The publication list delivered as friendly as possible for the LaTeX users, in the form of the familiar BibTeX data base, just copy-and-paste. Concerns only journal and conference papers. The formal links lead to contents elsewhere, this means: by the publishers. Thanks to papercite plugin.

2018

• Platzek, F. W., Stelling, G. S., Jankowski, J. A., Patzwahl, R., & Pietrzak, J. D.. (2018). River computations: artificial backwater from the momentum advection scheme. Journal of Hydraulic Research, 1-16. doi:10.1080/00221686.2017.1399935
  [BibTeX] [Abstract] [Download PDF]
  

  The established method for determining dike heights and dimensioning river training structures is to assess the resulting backwater by numerical modelling. The common consensus is that bottom friction determines the backwater and that momentum advection only has a local effect. We demonstrate that the numerical/artificial backwater contribution from the momentum advection approximation can be of the same order of magnitude as the bottom friction contribution, depending on the advection scheme. This is realized using a one-dimensional analysis and verified using a set of one- and two-dimensional test problems including a wavy bed case, flow over emerged and submerged groynes and finally an actual river. We compare first- and second-order accurate advection schemes and compute their artificial contribution to the backwater, for a range of practically-feasible grid resolutions. The tests demonstrate that the conservation/constancy properties of the scheme determine the size of this contribution, rather than the order of the scheme.

  @Article{Platzek2018,
  author = {Frank W. Platzek and Guus S. Stelling and Jacek A. Jankowski and Regina Patzwahl and Julie D. Pietrzak},
  journal = {Journal of Hydraulic Research},
  title = {River computations: artificial backwater from the momentum advection scheme},
  year = {2018},
  note = {Published online: 05 Mar 2018},
  number = {0},
  pages = {1-16},
  volume = {0},
  abstract = {The established method for determining dike heights and dimensioning river training structures is to assess the resulting backwater by numerical modelling. The common consensus is that bottom friction determines the backwater and that momentum advection only has a local effect. We demonstrate that the numerical/artificial backwater contribution from the momentum advection approximation can be of the same order of magnitude as the bottom friction contribution, depending on the advection scheme. This is realized using a one-dimensional analysis and verified using a set of one- and two-dimensional test problems including a wavy bed case, flow over emerged and submerged groynes and finally an actual river. We compare first- and second-order accurate advection schemes and compute their artificial contribution to the backwater, for a range of practically-feasible grid resolutions. The tests demonstrate that the conservation/constancy properties of the scheme determine the size of this contribution, rather than the order of the scheme.},
  doi = {10.1080/00221686.2017.1399935},
  eprint = {https://doi.org/10.1080/00221686.2017.1399935},
  owner = {jaj},
  publisher = {Taylor \& Francis},
  timestamp = {2018.03.10},
  url = {https://doi.org/10.1080/00221686.2017.1399935},
  }

2017

• Platzek, F. W., Stelling, G. S., Jankowski, J. A., Patzwahl, R., & Pietrzak, J. D.. (2017). Ein effizienter semi-impliziter Subgrid-Ansatz für Strömungen mit freier Oberfläche auf hierarchischen Gittern. BAW Mitteilungen, 2017(100), 207-224.
  [BibTeX] [Abstract] [Download PDF]
  

  German Abstract: Es wird eine neue Modellierstrategie zur Effizienzsteigerung rechenintensiver Simulationen von Flüssen vorgestellt. Der Ansatz kombiniert einen semi-impliziten Subgrid-Ansatz zur Berücksichtigung von hochaufgelösten Geländeinformationen auf gröberen Netzen mit einer auf Hierarchischen-Netzen basierenden Strategie. Diese Kombination führt zu einer Genauigkeits- und Effizienzsteigerung hydro-numerischer Flussmodelle sowohl im stationären als auch instationären Fall. Die hier präsentierte Arbeit beschränkt sich auf den stationären Fall und zeigt, dass der „Hierarchische-Gitter-Subgrid“-Ansatz zu einer bis zu 43-fachen Verringerung der Rechenzeiten führen kann. Zusätzlich gewährt die Methode einen direkten und automatisierten Einblick in das Gitterkonvergenzverhalten. Es werden die Effizienz und Anwendbarkeit des Ansatzes sowohl an einem schematischen Beispiel als auch an einem realen Flussmodell aufgezeigt. Diesem Beitrag liegt folgende Veröffentlichung zugrunde: Platzek et al. (2015): An efficient semi-implicit subgrid method for free-surface flows on hierarchical grids. Int. J. Numer. Meth. Fluids 80 (12): S. 715-741. DOI: 10.1002/fld.4172. Copyright © 2015 John Wiley & Sons, Ltd. English Abstract: A new modelling strategy for improving the efficiency of computationally intensive flow problems in environmental free-surface flows is presented. The approach combines a recently developed semi-implicit subgrid method with a hierarchical-grid solution strategy. The method allows the incorporation of high-resolution data on subgrid scale to obtain a more accurate and efficient hydrodynamic model. The subgrid method improves the efficiency of the hierarchical grid method by providing better solutions on coarse grids. The method is applicable to both steady and unsteady flows, although the particular focus here is on river flows with steady boundary conditions. There, the combined hierarchical grid-subgrid method reduces the computational effort to obtain a steady state with factors up to 43. Additionally, the method provides automatic insight in grid convergence. The efficiency and applicability of the method using a schematic test for the vortex shedding around a circular cylinder and a real-world river case study is demonstrated. This work is based on: Platzek et al. (2015): An efficient semi-implicit subgrid method for free-surface flows on hierarchical grids. Int. J. Numer. Meth. Fluids 80 (12): p. 715-741. DOI: 10.1002/fld.4172. Copyright © 2015 John Wiley & Sons, Ltd.

  @Article{Platzek2017,
  author = {Platzek, F.W. and Stelling, G.S. and Jankowski, J.A. and Patzwahl, R. and Pietrzak, J.D.},
  journal = {BAW Mitteilungen},
  title = {Ein effizienter semi-impliziter Subgrid-Ansatz für Strömungen mit freier Oberfläche auf hierarchischen Gittern},
  year = {2017},
  month = {March},
  number = {100},
  pages = {207-224},
  volume = {2017},
  abstract = {German Abstract: Es wird eine neue Modellierstrategie zur Effizienzsteigerung rechenintensiver Simulationen von Flüssen vorgestellt. Der Ansatz kombiniert einen semi-impliziten Subgrid-Ansatz zur Berücksichtigung von hochaufgelösten Geländeinformationen auf gröberen Netzen mit einer auf Hierarchischen-Netzen basierenden Strategie. Diese Kombination führt zu einer Genauigkeits- und Effizienzsteigerung hydro-numerischer Flussmodelle sowohl im stationären als auch instationären Fall. Die hier präsentierte Arbeit beschränkt sich auf den stationären Fall und zeigt, dass der „Hierarchische-Gitter-Subgrid“-Ansatz zu einer bis zu 43-fachen Verringerung der Rechenzeiten führen kann. Zusätzlich gewährt die Methode einen direkten und automatisierten Einblick in das Gitterkonvergenzverhalten. Es werden die Effizienz und Anwendbarkeit des Ansatzes sowohl an einem schematischen Beispiel als auch an einem realen Flussmodell aufgezeigt. Diesem Beitrag liegt folgende Veröffentlichung zugrunde: Platzek et al. (2015): An efficient semi-implicit subgrid method for free-surface flows on hierarchical grids. Int. J. Numer. Meth. Fluids 80 (12): S. 715-741. DOI: 10.1002/fld.4172. Copyright © 2015 John Wiley & Sons, Ltd.
  English Abstract: A new modelling strategy for improving the efficiency of computationally intensive flow problems in environmental free-surface flows is presented. The approach combines a recently developed semi-implicit subgrid method with a hierarchical-grid solution strategy. The method allows the incorporation of high-resolution data on subgrid scale to obtain a more accurate and efficient hydrodynamic model. The subgrid method improves the efficiency of the hierarchical grid method by providing better solutions on coarse grids. The method is applicable to both steady and unsteady flows, although the particular focus here is on river flows with steady boundary conditions. There, the combined hierarchical grid-subgrid method reduces the computational effort to obtain a steady state with factors up to 43. Additionally, the method provides automatic insight in grid convergence. The efficiency and applicability of the method using a schematic test for the vortex shedding around a circular cylinder and a real-world river case study is demonstrated. This work is based on: Platzek et al. (2015): An efficient semi-implicit subgrid method for free-surface flows on hierarchical grids. Int. J. Numer. Meth. Fluids 80 (12): p. 715-741. DOI: 10.1002/fld.4172. Copyright © 2015 John Wiley & Sons, Ltd.},
  keywords = {advection schemes, computational efficiency, free surface flows, grid convergence, hierarchical grids, steady-state computations, subgrid, validation, verification},
  owner = {jaj},
  timestamp = {2017.04.18},
  url = {https://hdl.handle.net/20.500.11970/102499},
  }

2016

• Platzek, F. W., Stelling, G. S., Jankowski, J. A., Patzwahl, R., & Pietrzak, J. D.. (2016). An efficient semi-implicit subgrid method for free-surface flows on hierarchical grids. International Journal for Numerical Methods in Fluids, 80(12), 715–741. doi:10.1002/fld.4172
  [BibTeX] [Abstract] [Download PDF]
  

  We present a new modelling strategy for improving the efficiency of computationally intensive flow problems in environmental free-surface flows. The approach combines a recently developed semi-implicit subgrid method with a hierarchical grid solution strategy. The method allows the incorporation of high-resolution data on subgrid scale to obtain a more accurate and efficient hydrodynamic model. The subgrid method improves the efficiency of the hierarchical grid method by providing better solutions on coarse grids. The method is applicable to both steady and unsteady flows, but we particularly focus on river flows with steady boundary conditions. There, the combined hierarchical grid–subgrid method reduces the computational effort to obtain a steady state with factors up to 43. For unsteady models, the method can be used for efficiently generating accurate initial conditions on high-resolution grids. Additionally, the method provides automatic insight in grid convergence. We demonstrate the efficiency and applicability of the method using a schematic test for the vortex shedding around a circular cylinder and a real-world river case study.

  @Article{Platzek2016,
  author = {Platzek, F. W. and Stelling, G. S. and Jankowski, J. A. and Patzwahl, R. and Pietrzak, J. D.},
  journal = {International Journal for Numerical Methods in Fluids},
  title = {An efficient semi-implicit subgrid method for free-surface flows on hierarchical grids},
  year = {2016},
  issn = {1097-0363},
  note = {fld.4172},
  number = {12},
  pages = {715--741},
  volume = {80},
  abstract = {We present a new modelling strategy for improving the efficiency of computationally intensive flow problems in environmental free-surface flows. The approach combines a recently developed semi-implicit subgrid method with a hierarchical grid solution strategy. The method allows the incorporation of high-resolution data on subgrid scale to obtain a more accurate and efficient hydrodynamic model. The subgrid method improves the efficiency of the hierarchical grid method by providing better solutions on coarse grids. The method is applicable to both steady and unsteady flows, but we particularly focus on river flows with steady boundary conditions. There, the combined hierarchical grid–subgrid method reduces the computational effort to obtain a steady state with factors up to 43. For unsteady models, the method can be used for efficiently generating accurate initial conditions on high-resolution grids. Additionally, the method provides automatic insight in grid convergence. We demonstrate the efficiency and applicability of the method using a schematic test for the vortex shedding around a circular cylinder and a real-world river case study.},
  doi = {10.1002/fld.4172},
  keywords = {subgrid method, hierarchical grids, grid convergence, efficiency, steady-state computations, shallow water},
  owner = {jaj},
  timestamp = {2015.09.07},
  url = {http://dx.doi.org/10.1002/fld.4172},
  }

• Rustico, E., & Jankowski, J. A.. (2016). Evaluation and adaption of the SPH method for hydraulic engineering problems on federal waterways (final reportNo. B3953.05.04.70002). Bundesanstalt für Wasserbau (BAW).
  [BibTeX] [Abstract] [Download PDF]
  

  Smoothed Particle Hydrodynamics (SPH) is a Lagrangian method for fluid dynamic simulations. In the past decades it drew the attention of the scientific community for its versatility and the possibility to simulate complex phenomena such as e.g. surface tension and fluid-solid interactions with floating objects. SPH has in general higher computational requirements than the most common Eulerian methods and several different models have been proposed for the treatment of boundaries, each with advantages and limitations. The project aimed to develop, validate and increase the computational efficiency of an existing SPH code for hydraulic engineering problems. As base code for the development, the GPUSPH simulator has been chosen. As the name suggests, it is a SPH implementation which exploits the Graphic Processing Units (GPU) to perform the computation of the particle to particle interactions. The GPUSPH simulator has been developed within the ATHOS Consortium, whose members include universities and research institutes from different nations working on different aspects of the code. A development branch external to BAW butof particular interest for the project regards the newer “Semi-Analytical” boundary model, the development of which has been completed only recently. In the first phase, several features have been improved or introduced in the simulator, especially the capability of splitting a simulation across multiple nodes of a cluster each equipped with one or more GPU devices. This additional level of parallelism has enabled the simulation of high-resolution or spatially big scenarios (more than 100 million particles). In the second phase, two test cases have been developed. The first is a fish pass, that has been modeled following the plan of a physical scaled model situated in the laboratories of BAW Karlsruhe. Simple Lennard-Jones boundaries have been used, featuring “pseudo-open” boundaries capable of controlling the inlet flow and specifically developed for the test case. A comparison of the simulated flow and a set of laboratory measurements highlighted a very good agreement in terms of the stream shape, including the recirculation areas. The water level were however too high in the simulated model because of an excess of friction due to the boundary model. A ship lock has been modeled as second test case replicating the new Kiel-Holtenau lock, of which a scaled model was built at BAW Karlsruhe. The first implementation used the Semi-Analytical boundaries, featuring pressure- or velocity-driver open boundaries. Although the first results appeared to be promising, the low computational performance of the boundary model made a continuation of the tests on a large scale infeasible. Since a performance-optimized version of the model was not yet available (and is still in progress within the consortium), a second attempt has been done with the Dynamic Boundaries, a lighter boundary model featuring correct pressure at the boundaries but no inlets. The water inflow has been implemented either with “pseudo-inlet” and with a piston chamber. Both attempts showed a strong artifact causing the stream flow to go upward and hit the ship frontally rather than passing under it. This yielded the forces acting on the ship to be stronger than the forces measured in a laboratory model at BAW. The causes of the difference have been identified with high probability in the artificial stream lift caused by the non-physical inlet and the excess of friction along the ship hull. Both factors could be eliminated with a more physics-adherent boundary model. The test cases highlighted the limits of the simpler boundary models and the need for an optimized, industrial-level version of the newly developed Semi-Analytical boundaries. Although the current development status and the first results are very promising for the applicability of the method to complex real-life engineering problems, and are already being used in the scientific community for many simpler problem scenarios, an optimization of the new boundary model is crucial to free the high potential of the method and accurately determine its application range and characteristics. An additional time of at least one year would be required to re-implement both test cases with the new model and produce a definitive comparison, granted the availability of the consortium members involving the optimization of the boundary model.

  @TechReport{Rustico2016final,
  author = {Rustico, E. and Jankowski, J.A.},
  institution = {Bundesanstalt für Wasserbau (BAW)},
  title = {Evaluation and adaption of the SPH method for hydraulic engineering problems on federal waterways},
  year = {2016},
  number = {B3953.05.04.70002},
  type = {final report},
  abstract = {Smoothed Particle Hydrodynamics (SPH) is a Lagrangian method for fluid dynamic simulations. In the past decades it drew the attention of the scientific community for its versatility and the possibility to simulate complex phenomena such as e.g. surface tension and fluid-solid interactions with floating objects. SPH has in general higher computational requirements than the most common Eulerian methods and several different models have been proposed for the treatment of boundaries, each with advantages and limitations.
  The project aimed to develop, validate and increase the computational efficiency of an existing SPH code for hydraulic engineering problems. As base code for the development, the GPUSPH simulator has been chosen. As the name suggests, it is a SPH implementation which exploits the Graphic Processing Units (GPU) to perform the computation of the particle to particle interactions. The GPUSPH simulator has been developed within the ATHOS Consortium, whose members include universities and research institutes from different nations working on different aspects of the code. A development branch external to BAW butof particular interest for the project regards the newer “Semi-Analytical” boundary  model, the development of which has been completed only recently.
  In the first phase, several features have been improved or introduced in the simulator, especially the capability of splitting a simulation across multiple nodes of a cluster each equipped with one or more GPU devices. This additional level of parallelism has enabled the simulation of high-resolution or spatially big scenarios (more than 100 million particles).
  In the second phase, two test cases have been developed. The first is a fish pass, that has been modeled following the plan of a physical scaled model situated in the laboratories of BAW Karlsruhe. Simple Lennard-Jones boundaries have been used, featuring “pseudo-open” boundaries capable of controlling the inlet flow and specifically developed for the test case. A comparison of the simulated flow and a set of laboratory measurements highlighted a very good agreement in terms of the stream shape, including the recirculation areas. The water level were however too high in the simulated model because of an excess of friction due to the boundary model.
  A ship lock has been modeled as second test case replicating the new Kiel-Holtenau lock, of which a scaled model was built at BAW Karlsruhe. The first implementation used the Semi-Analytical boundaries, featuring pressure- or velocity-driver open boundaries. Although the first results appeared to be promising, the low computational performance of the boundary model made a continuation of the tests on a large scale infeasible. Since a performance-optimized version of the model was not yet available (and is still in progress within the consortium), a second attempt has been done with the Dynamic Boundaries, a lighter boundary model featuring correct pressure at the boundaries but no inlets. The water inflow has been implemented either with “pseudo-inlet” and with a piston chamber. Both attempts showed a strong artifact causing the stream flow to go upward and hit the ship frontally rather than passing under it. This yielded the forces acting on the ship to be stronger than the forces measured in a laboratory model at BAW. The causes of the difference have been identified with high probability in the artificial stream lift caused by the non-physical inlet and the excess of friction along the ship hull. Both factors could be eliminated with a more physics-adherent boundary model.
  The test cases highlighted the limits of the simpler boundary models and the need for an optimized, industrial-level version of the newly developed Semi-Analytical boundaries. Although the current development status and the first results are very promising for the applicability of the method to complex real-life engineering problems, and are already being used in the scientific community for many simpler problem scenarios, an optimization of the new boundary model is crucial to free the high potential of the method and accurately determine its application range and characteristics. An additional time of at least one year would be required to re-implement both test cases with the new model and produce a definitive comparison, granted the availability of the consortium members involving the optimization of the boundary model.},
  owner = {jaj},
  timestamp = {2017.02.27},
  url = {https://hdl.handle.net/20.500.11970/105111},
  }

2014

• Jankowski, J. A.. (2014). Potential der Intel Many Integrated Core Architektur für die Flussmodellierung – Codes UnTRIM und TELEMAC (Internal ReportNo. A39530510012). BAW.
  [BibTeX] [Abstract] [Download PDF]
  

  In der Einführung werden die Aspekte der heterogenen Rechnerarchitekturen mit der besonderen Berücksichtigung von Beschleunigern zusammen mit den gängigen Programmiermethoden beschrieben. Auf dieser Basis werden die Eigenschaften des neuen Intel Xeon Phi Prozessors vorgestellt, der in der heute gegebenen Form eine neue Art von Beschleuniger ist. Es werden die Eigenschaften der Systemsoftware, Programmiertechniken und existierende Entwicklungswerkzeuge diskutiert. Es werden genaue Spezifikationen für die verwendete Hardware geliefert. Nach dieser Einführung werden die getroffenen Annahmen und die minimalen Anpassungen notwendig für die Untersuchung der Leistungsfähigkeit des Xeon Phi Prozessors für den Code von UnTRIM2 – und für einen Vergleich auch mit den deutlich älteren Codes Telemac3D und Telemac2D – erortert. Der Code von UnTRIM2 wurde unverändert, nur mit modifizierten Compilereinstellungen, Makefiles, Umgebungsvariablen für OpenMP und MPI und Laufskripten angewendet. Genauso für Telemac3D und Telemac2D, bei denen zusätzlich noch einige Fehler im Code teilweise beseitigt werden mussten. Bei allen Einstellungen hat man sich an die allgemeinen Empfehlungen der Firma Intel für numerische Programme orientiert, die sich auch nach rudimentären Tests als korrekt erwiesen haben. Es handelt sich hier also um eine Voruntersuchung im Sinne einer sog. “naiven Portierung” der o.g. Codes ohne eine gezielte Optimierung zu wagen. Die Programme wurden auf der Xeon Phi Karte (60 Rechenkerne) alleine in dem sog. nativen Modus ausgeführt und die Rechenzeiten mit den Resultaten aus einem two-socket CPU-basierten System (zwei Xeon Prozessoren im Tandem, je mit 8 Rechenkernen) verglichen – d.h. mit einem System, welches im Sinne des Energieverbrauchs und des aktuellen Preises ähnlich ist. Bei allen Beispielen zeite sich, dass die besten erzielten Rechenzeiten mit einem Xeon Phi um ein Vielfaches (3-6 Mal) schlechter waren, als auf dem entsprechenden CPU-System. Es wurden dabei auch rudimentäre Untersuchungen für die Autovektorisierung der Programme gemacht. Es zeigte sich hiermit, dass obwohl die Portierung der älteren Codes auf die Xeon Phi mit Intel Entwicklungswerkzeugen ausgesprochen einfach ist, die Programme suboptimal ausgeführt werden. Diese Resultate sind konsistent mit Ergebnissen von anderen naiven Portierungen komplexer Codes für die MIC-Architektur. Anschliessend wird das Potential der angezielten Optimierung der untersuchten Codes diskutiert, insbesondere im Hinblick auf die Hardwareanforderungen und bekannten Entwicklungspläne der Firma Intel. Von allen Codes hat UnTRIM, bzw. der grundlegende Algorithmus oder die bereits existierenden Nachfolgeprogramme die besten Aussichten.

  @TechReport{Jankowski2014mic,
  author = {Jankowski, J.A.},
  institution = {BAW},
  title = {{Potential der Intel Many Integrated Core Architektur für die Flussmodellierung – Codes UnTRIM und TELEMAC}},
  year = {2014},
  number = {A39530510012},
  type = {Internal Report},
  abstract = {In der Einführung werden die Aspekte der heterogenen Rechnerarchitekturen mit der besonderen Berücksichtigung von Beschleunigern zusammen mit den gängigen Programmiermethoden beschrieben. Auf dieser Basis werden die Eigenschaften des neuen Intel Xeon Phi Prozessors vorgestellt, der in der heute gegebenen Form eine neue Art von Beschleuniger ist. Es werden die Eigenschaften der Systemsoftware, Programmiertechniken und existierende Entwicklungswerkzeuge diskutiert. Es werden genaue Spezifikationen für die verwendete Hardware geliefert.
  Nach dieser Einführung werden die getroffenen Annahmen und die minimalen Anpassungen notwendig für die Untersuchung der Leistungsfähigkeit des Xeon Phi Prozessors für den Code von UnTRIM2 – und für einen Vergleich auch mit den deutlich älteren Codes Telemac3D und Telemac2D – erortert. Der Code von UnTRIM2 wurde unverändert, nur mit modifizierten Compilereinstellungen, Makefiles, Umgebungsvariablen für OpenMP und MPI und Laufskripten angewendet. Genauso für Telemac3D und Telemac2D, bei denen zusätzlich noch einige Fehler im Code teilweise beseitigt werden mussten. Bei allen Einstellungen hat man sich an die allgemeinen Empfehlungen der Firma Intel für numerische Programme orientiert, die sich auch nach rudimentären Tests als korrekt erwiesen haben. Es handelt sich hier also um eine Voruntersuchung im Sinne einer sog. “naiven Portierung” der o.g. Codes ohne eine gezielte Optimierung zu wagen.
  Die Programme wurden auf der Xeon Phi Karte (60 Rechenkerne) alleine in dem sog. nativen Modus ausgeführt und die Rechenzeiten mit den Resultaten aus einem two-socket CPU-basierten System (zwei Xeon Prozessoren im Tandem, je mit 8 Rechenkernen) verglichen – d.h. mit einem System, welches im Sinne des Energieverbrauchs und des aktuellen Preises ähnlich ist.
  Bei allen Beispielen zeite sich, dass die besten erzielten Rechenzeiten mit einem Xeon Phi um ein Vielfaches (3-6 Mal) schlechter waren, als auf dem entsprechenden CPU-System. Es wurden dabei auch rudimentäre Untersuchungen für die Autovektorisierung der Programme gemacht. Es zeigte sich hiermit, dass obwohl die Portierung der älteren Codes auf die Xeon Phi mit Intel Entwicklungswerkzeugen ausgesprochen einfach ist, die Programme suboptimal ausgeführt werden. Diese Resultate sind konsistent mit Ergebnissen von anderen naiven Portierungen komplexer Codes für die MIC-Architektur.
  Anschliessend wird das Potential der angezielten Optimierung der untersuchten Codes diskutiert, insbesondere im Hinblick auf die Hardwareanforderungen und bekannten Entwicklungspläne der Firma Intel. Von allen Codes hat UnTRIM, bzw. der grundlegende Algorithmus oder die bereits existierenden Nachfolgeprogramme die besten Aussichten.},
  owner = {jaj},
  timestamp = {2016.08.18},
  url = {http://papers.jankowski.org/intel-many-integrated-core-mic-architecture-and-the-untrim-code},
  }

• Platzek, F. W., Stelling, G. S., Jankowski, J. A., & Pietrzak, J. D.. (2014). Accurate vertical profiles of turbulent flow in z-layer models. Water Resources Research, 50(3), 2191–2211. doi:10.1002/2013WR014411
  [BibTeX] [Abstract] [Download PDF]
  

  Three-dimensional hydrodynamic z-layer models, which are used for simulating the flow in rivers, estuaries, and oceans, suffer from an inaccurate and often discontinuous bottom shear stress representation, due to the staircase bottom. We analyze the governing equations and clearly show the cause of the inaccuracies. Based on the analysis, we present a new method that significantly reduces the errors and the grid dependency of the results. The method consists of a near-bed layer-remapping and a modified near-bed discretization of the k − ε turbulence model. We demonstrate the applicability of the approach for uniform channel flow, using a schematized two-dimensional vertical model and for the flow over a bottom sill using the Delft3D modeling system.

  @Article{Platzek2014a,
  author = {Platzek, F. W. and Stelling, G. S. and Jankowski, J. A. and Pietrzak, J. D.},
  journal = {Water Resources Research},
  title = {Accurate vertical profiles of turbulent flow in z-layer models},
  year = {2014},
  issn = {1944-7973},
  number = {3},
  pages = {2191--2211},
  volume = {50},
  abstract = {Three-dimensional hydrodynamic z-layer models, which are used for simulating the flow in rivers, estuaries, and oceans, suffer from an inaccurate and often discontinuous bottom shear stress representation, due to the staircase bottom. We analyze the governing equations and clearly show the cause of the inaccuracies. Based on the analysis, we present a new method that significantly reduces the errors and the grid dependency of the results. The method consists of a near-bed layer-remapping and a modified near-bed discretization of the k − ε turbulence model. We demonstrate the applicability of the approach for uniform channel flow, using a schematized two-dimensional vertical model and for the flow over a bottom sill using the Delft3D modeling system.},
  doi = {10.1002/2013WR014411},
  keywords = {Hydrodynamic modeling, Turbulence, diffusion, and mixing processes, Topographic/bathymetric interactions, Numerical modeling, Hydrodynamics, boundary layer flow, z-coordinates, discretization errors, k-epsilon turbulence, staircase problem},
  owner = {jaj},
  timestamp = {2015.09.07},
  url = {http://dx.doi.org/10.1002/2013WR014411},
  }

• Rustico, E., Jankowski, J., Hérault, A., Bilotta, G., & Del Negro, C.. (2014). Multi-GPU, multi-node SPH implementation with arbitrary domain decomposition. Paper presented at the Proceedings of the 9th SPHERIC International Workshop.
  [BibTeX] [Abstract] [Download PDF]
  

  We present a restructured version of GPUSPH [4], [8], [11], a CUDA-based implementation of SPH. The new version is extended to allow execution on multiple GPUs on one or more host nodes, making it possible to concurrently exploit hundreds of devices across a network, allowing the simulation on larger domains and at higher resolutions. Partitioning of the computational domain is not limited anymore to parallel planes and can follow arbitrary, user-defined shapes at the resolution of individual cells, where the cell is defined by the auxiliary grid used for fast neighbor search. This allows optimal partitioning even in the case of complex domains, such as rivers with Uturns. The version we present also includes many additional features that have been developed on GPUSPH. Particularly important are: the uniform precision work by H´erault et al. [13], which is essential for numerical robustness in the case of very large ratios between the domain size and particle resolution; a compact neighbor list, which allows larger subdomains to be loaded on each device; the semi-analytical boundary conditions by Ferrand et al. [9], [12], and support for floating objects [14]. All of these features are seamlessly supported in single-GPU, multi-GPU and multi-node modes.

  @InProceedings{Rustico2014b,
  author = {Rustico, E. and Jankowski, J. and Hérault, A. and Bilotta, G. and Del Negro, C.},
  booktitle = {Proceedings of the 9th SPHERIC International Workshop},
  title = {Multi-{GPU}, multi-node {SPH} implementation with arbitrary domain decomposition},
  year = {2014},
  editor = {Damien Violeau, Alexis Hérault, Antoine Joly},
  month = {Paris, France, June, 03-05 2014},
  organization = {CNAM, Paris, France},
  pages = {127--133},
  abstract = {We present a restructured version of GPUSPH [4], [8], [11], a CUDA-based implementation of SPH. The new version is extended to allow execution on multiple GPUs on one or more host nodes, making it possible to concurrently exploit hundreds of devices across a network, allowing the simulation on larger domains and at higher resolutions. Partitioning of the computational domain is not limited anymore to parallel planes and can follow arbitrary, user-defined shapes at the resolution of individual cells, where the cell is defined by the auxiliary grid used for fast neighbor search. This allows optimal partitioning even in the case of complex domains, such as rivers with Uturns. The version we present also includes many additional features that have been developed on GPUSPH. Particularly important are: the uniform precision work by H´erault et al. [13], which is essential for numerical robustness in the case of very large ratios between the domain size and particle resolution; a compact neighbor list, which allows larger subdomains to be loaded on each device; the semi-analytical boundary conditions by Ferrand et al. [9], [12], and support for floating objects [14]. All of these features are seamlessly supported in single-GPU, multi-GPU and multi-node modes.},
  owner = {jaj},
  timestamp = {2014.06.23},
  url = {https://hdl.handle.net/20.500.11970/100905},
  }

2013

• Jankowski, J. A.. (2013). Adaptierung und Erweiterung von Casulli-Algorithmen für Parallelrechner mit Hardware-Beschleunigung und zur Anwendung von konservativen Advektionsverfahren (AbschlußberichtNo. A39530270001). Bundesanstalt für Wasserbau.
  [BibTeX] [Abstract] [Download PDF]
  

  Abstract: The aim of the R&D-project is development and application of new programming paradigms in high performance computing through the adaptation of Casulli algorithms for arriving parallel computer architectures with hardware acceleration. Additionally, the existing advection schemes should be adapted for all flow regimes. Zusammenfassung: Das Ziel des F&E-Vorhabens ist Erarbeitung und Anwendung neuer Programmierparadigmen im Hochleistungsrechnen durch die Adaptierung von Casulli-Algorithmen für kommende Parallelrechner-Architekturen mit Hardware-Beschleunigung. Zusätzlich sollen die vorhandenen Advektionsverfahren für alle Abflussarten angepasst werden.

  @TechReport{Jankowski2013hard,
  author = {Jankowski, J.A.},
  institution = {Bundesanstalt für Wasserbau},
  title = {{Adaptierung und Erweiterung von Casulli-Algorithmen für Parallelrechner mit Hardware-Beschleunigung und zur Anwendung von konservativen Advektionsverfahren}},
  year = {2013},
  month = {Januar 2013},
  note = {62pp.},
  number = {A39530270001},
  type = {Abschlußbericht},
  abstract = {Abstract: The aim of the R&D-project is development and application of new programming paradigms in high performance computing through the adaptation of Casulli algorithms for arriving parallel computer architectures with hardware acceleration. Additionally, the existing advection schemes should be adapted for all flow regimes.
  Zusammenfassung: Das Ziel des F&E-Vorhabens ist Erarbeitung und Anwendung neuer Programmierparadigmen im Hochleistungsrechnen durch die Adaptierung von Casulli-Algorithmen für kommende Parallelrechner-Architekturen mit Hardware-Beschleunigung. Zusätzlich sollen die vorhandenen Advektionsverfahren für alle Abflussarten angepasst werden.},
  file = {:http\://www.baw.de/content/files/forschung_entwicklung/documents/A39530270001.pdf:PDF},
  owner = {jaj},
  timestamp = {2013.10.30},
  url = {http://papers.jankowski.org/adaptierung-und-erweiterung-von-casulli-algorithmen-fur-parallelrechner-mit-hardware-beschleunigung-und-zur-anwendung-von-konservativen-advektionsverfahren},
  }

2012

• Jankowski, J. A.. (2012). A hardware-accelerated parallel implementation of a two-dimensional scheme for free surface flows. Paper presented at the Proceedings of HIC 2012 – 10th International Conference on Hydroinformatics, Hamburg, July 14-18, 2012.
  [BibTeX] [Abstract] [Download PDF]
  

  This contribution concerns the verification and performance assessment of a hardware-accelerated parallel implementation of an algorithm for the semi-implicit finite difference method for solving the vertically integrated shallow water equations including a non-linear treatment of wetting and drying and conservative advection schemes. Instead of adapting an existing serial, OpenMP-, or MPI-parallelised code with all necessary compromises to be met, the selected approach is to write the code from scratch exposing the fine-grained parallelism of the scheme and execute the whole computational kernel of the code on a state-of-the-art streaming processor, i.e. a GPU. The reached speedups compared to a single CPU core are in the order of 20 or 30 for the double or single precision, respectively, which confirms the attractivity of the presently available advanced programming technologies for detailed, high-resolution river modelling applying commodity hardware.

  @InProceedings{Jankowski2012,
  author = {Jankowski, J.A.},
  booktitle = {Proceedings of HIC 2012 -- 10th International Conference on Hydroinformatics, Hamburg, July 14-18, 2012},
  title = {A hardware-accelerated parallel implementation of a two-dimensional scheme for free surface flows},
  year = {2012},
  note = {Hamburg, Germany},
  publisher = {TuTech Verlag},
  abstract = {This contribution concerns the verification and performance assessment of a hardware-accelerated parallel implementation of an algorithm for the semi-implicit finite difference method for solving the vertically integrated shallow water equations including a non-linear treatment of wetting and drying and conservative advection schemes. Instead of adapting an existing serial, OpenMP-, or MPI-parallelised code with all necessary compromises to be met, the selected approach is to write the code from scratch exposing the fine-grained parallelism of the scheme and execute the whole computational kernel of the code on a state-of-the-art streaming processor, i.e. a GPU. The reached speedups compared to a single CPU core are in the order of 20 or 30 for the double or single precision, respectively, which confirms the attractivity of the presently available advanced programming technologies for detailed, high-resolution river modelling applying commodity hardware.},
  url = {https://hdl.handle.net/20.500.11970/100838},
  }

• Platzek, F., Stelling, G. S., Jankowski, J. A., & Patzwahl, R.. (2012). On the representation of bottom shear stress in z-layer models. Paper presented at the Proceedings of HIC 2012 – 10th International Conference on Hydroinformatics, Hamburg, July 14-18, 2012.
  [BibTeX] [Abstract] [Download PDF]
  

  Bottom friction plays an important role in modelling river flows. In three-dimensional (3D) models, the vertical discretization is commonly based on σ-layers or z-layers. In this paper we focus on a well-known problem encountered when applying z-layers: local truncation errors in the computation of bottom shear stress and near-bed turbulence along a sloping bottom as e.g. in the case of 3D river simulations. This problem stems from the ‘staircase’ representation of the bottom and results in difficulties in the computation of morphological changes. We consider uniform channel flow and analyze the influence of variations in near- bed layer thickness on the local truncation errors in the vertical diffusion term. Application of both an algebraic turbulence model, based on a prescribed mixing-length and the standard k-ε turbulence model to compute the eddy viscosity is investigated. We consider two approaches that reduce the local truncation errors and inspect their applicability for more general flow situations.

  @InProceedings{Platzek2012,
  author = {Platzek, F. and Stelling, G.S. and Jankowski, J.A. and Patzwahl, R.},
  booktitle = {Proceedings of HIC 2012 - 10th International Conference on Hydroinformatics, Hamburg, July 14-18, 2012},
  title = {On the representation of bottom shear stress in z-layer models},
  year = {2012},
  note = {Hamburg, Germany},
  publisher = {TuTech Verlag},
  abstract = {Bottom friction plays an important role in modelling river flows. In three-dimensional (3D) models, the vertical discretization is commonly based on σ-layers or z-layers. In this paper we focus on a well-known problem encountered when applying z-layers: local truncation errors in the computation of bottom shear stress and near-bed turbulence along a sloping bottom as e.g. in the case of 3D river simulations. This problem stems from the ‘staircase’ representation of the bottom and results in difficulties in the computation of morphological changes. We consider uniform channel flow and analyze the influence of variations in near- bed layer thickness on the local truncation errors in the vertical diffusion term. Application of both an algebraic turbulence model, based on a prescribed mixing-length and the standard k-ε turbulence model to compute the eddy viscosity is investigated. We consider two approaches that reduce the local truncation errors and inspect their applicability for more general flow situations.},
  url = {https://hdl.handle.net/20.500.11970/106398},
  }

2009

• Jankowski, J. A.. (2009). Parallel implementation of a non-hydrostatic model for free surface flows with semi-Lagrangian advection treatment. International Journal for Numerical Methods in Fluids, 59(10), 1157–1179. doi:10.1002/fld.1859
  [BibTeX] [Abstract] [Download PDF]
  

  The parallel implementation of an unstructured-grid, three-dimensional, semi-implicit finite difference and finite volume model for the free surface Navier–Stokes equations (UnTRIM) is presented and discussed. The new developments are aimed to make the code available for high-performance computing in order to address larger, complex problems in environmental free surface flows. The parallelization is based on the mesh partitioning method and message passing and has been achieved without negatively affecting any of the advantageous properties of the serial code, such as its robustness, accuracy and efficiency. The key issue is a new, autonomous parallel streamline backtracking algorithm, which allows using semi-Lagrangian methods in decomposed meshes without compromising the scalability of the code. The implementation has been carefully verified not only with simple, abstract test cases illustrating the application domain of the code but also with advanced, high-resolution models presently applied for research and engineering projects. The scheme performance and accuracy aspects are researched and discussed.

  @Article{Jankowski2009,
  author = {Jankowski, J.A.},
  journal = {International Journal for Numerical Methods in Fluids},
  title = {Parallel implementation of a non-hydrostatic model for free surface flows with semi-Lagrangian advection treatment},
  year = {2009},
  number = {10},
  pages = {1157--1179},
  volume = {59},
  abstract = {The parallel implementation of an unstructured-grid, three-dimensional, semi-implicit finite difference and finite volume model for the free surface Navier–Stokes equations (UnTRIM) is presented and discussed. The new developments are aimed to make the code available for high-performance computing in order to address larger, complex problems in environmental free surface flows. The parallelization is based on the mesh partitioning method and message passing and has been achieved without negatively affecting any of the advantageous properties of the serial code, such as its robustness, accuracy and efficiency. The key issue is a new, autonomous parallel streamline backtracking algorithm, which allows using semi-Lagrangian methods in decomposed meshes without compromising the scalability of the code. The implementation has been carefully verified not only with simple, abstract test cases illustrating the application domain of the code but also with advanced, high-resolution models presently applied for research and engineering projects. The scheme performance and accuracy aspects are researched and discussed.},
  doi = {10.1002/fld.1859},
  keywords = {parallel; free surface; non-hydrostatic; semi-Lagrangian; unstructured grid; UnTRIM},
  url = {http://onlinelibrary.wiley.com/doi/10.1002/fld.1859/abstract},
  }

2008

• Jankowski, J. A.. (2008). Mathematical model UnTRIM – MPI version manual (Technical Report). Bundes\-anstalt für Wasser\-bau, Karlsruhe.
  [BibTeX] [Abstract] [Download PDF]
  

  This document is aimed to provide the user of the MPI version of UnTRIM with necessary information for the installation, compilation and especially execution of the software.

  @TechReport{Jankowski2008mpi,
  author = {Jankowski, J.A.},
  institution = {Bundes\-anstalt für Wasser\-bau, Karlsruhe},
  title = {{Mathematical model UnTRIM -- MPI version manual}},
  year = {2008},
  note = {Version August 2008 (1.0), 55~pp.},
  type = {Technical Report},
  abstract = {This document is aimed to provide the user of the MPI version of UnTRIM with necessary information for the installation, compilation and especially execution of the software.},
  file = {manual_mpi_untrim.pdf:http\://www.baw.de/downloads/wasserbau/mathematische_verfahren/pdf/:PDF},
  url = {http://papers.jankowski.org/mathematical-model-untrim-mpi-version-manual},
  }

• Patzwahl, R., Jankowski, J. A., & Lege, T.. (2008). Very high resolution numerical modelling for inland waterway design. Paper presented at the Proceedings of the International Conference on Fluvial Hydraulics (River Flow 2008).
  [BibTeX] [Abstract] [Download PDF]
  

  The paper discusses the advantages and disadvantages of numerical modelling of rivers with a grid of very high resolution using the new MPI version of UnTRIM as the computational engine. The main aim of the investigation is to assess the economy of this approach taking especially into account the effort required for the mesh generation and its modification, which is usually laborious in the case of coarser meshes requiring exact reproduction of structure lines defining the flow. In the first step the results of a low-resolution Telemac-2D grid are compared to the results obtained for the same river stretch topography with a high-resolution UnTRIM model. In the second step the results of two- and three-dimensional modelling applying a high-resolution mesh based on a high quality digital terrain model are studied. It is concluded that under the assumption of appropriate computational resources readily available, the high-resolution modelling reduces significantly the effort required for the initial model set-up and for adjustments due to changes in the model topography. The calibration, parametrisation and validation of the models is simplified without affecting the accuracy, freeing the engineer to concentrate on the project aims and not bypass the weak points of the methodology.

  @InProceedings{Patzwahl2008,
  author = {Patzwahl, R. and Jankowski, J.A. and Lege, T.},
  booktitle = {Proceedings of the International Conference on Fluvial Hydraulics (River Flow 2008)},
  title = {Very high resolution numerical modelling for inland waterway design},
  year = {2008},
  note = {Izmir, Turkey, 2008},
  abstract = {The paper discusses the advantages and disadvantages of numerical modelling of rivers with a grid of very high resolution using the new MPI version of UnTRIM as the computational engine. The main aim of the investigation is to assess the economy of this approach taking especially into account the effort required for the mesh generation and its modification, which is usually laborious in the case of coarser meshes requiring exact reproduction of structure lines defining the flow. In the first step the results of a low-resolution Telemac-2D grid are compared to the results obtained for the same river stretch topography with a high-resolution UnTRIM model. In the second step the results of two- and three-dimensional modelling applying a high-resolution mesh based on a high quality digital terrain model are studied. It is concluded that under the assumption of appropriate computational resources readily available, the high-resolution modelling reduces significantly the effort required for the initial model set-up and for adjustments due to changes in the model topography. The calibration, parametrisation and validation of the models is simplified without affecting the accuracy, freeing the engineer to concentrate on the project aims and not bypass the weak points of the methodology.},
  url = {http://papers.jankowski.org/very-high-resolution-numerical-modelling-for-inland-waterway-design},
  }

2007

• Jankowski, J. A.. (2007). Further developments of UnTRIM: parallel implementation and its verification. Paper presented at the Proceedings of the IAHR Fifth International Symposium on Environmental Hydraulics, (ISEH V), Tempe, Arizona, USA.
  [BibTeX] [Abstract] [Download PDF]
  

  This contribution deals with further developments of UnTRIM, an unstructured-grid, three-dimensional, semi-implicit finite difference finite volume model for the shallow water equations (Casulli, 2002). Attractive numerical properties of the method like its robustness due to the unlimited stability and successes in practical applications spawned efforts aimed at making the available code fit for the high performance computing in order to address larger, complex problems in hydraulic engineering. The paper concentrates on the parallel implementation of the program, based on the domain decomposition method and message passing, which has been achieved without negatively affecting any of the properties of the serial code. A special attention is paid to a new, autonomous parallel streamline backtracking algorithm, which allows using semi-Lagrangian methods in decomposed meshes without compromising the scalability of the code. The new developments have been carefully verified not only with the numerous simple, abstract test cases illustrating the application domain of the code, but also with advanced, high resolution models presently applied for research and engineering projects.

  @InProceedings{Jankowski2007,
  author = {Jankowski, J.A.},
  booktitle = {Proceedings of the IAHR Fifth International Symposium on Environmental Hydraulics, (ISEH V)},
  title = {{Further developments of UnTRIM: parallel implementation and its verification}},
  year = {2007},
  address = {Tempe, Arizona, USA},
  organization = {IAHR},
  publisher = {IAHR},
  abstract = {This contribution deals with further developments of UnTRIM, an unstructured-grid, three-dimensional, semi-implicit finite difference finite volume model for the shallow water equations (Casulli, 2002). Attractive numerical properties of the method like its robustness due to the unlimited stability and successes in practical applications spawned efforts aimed at making the available code fit for the high performance computing in order to address larger, complex problems in hydraulic engineering. The paper concentrates on the parallel implementation of the program, based on the domain decomposition method and message passing, which has been achieved without negatively affecting any of the properties of the serial code. A special attention is paid to a new, autonomous parallel streamline backtracking algorithm, which allows using semi-Lagrangian methods in decomposed meshes without compromising the scalability of the code. The new developments have been carefully verified not only with the numerous simple, abstract test cases illustrating the application domain of the code, but also with advanced, high resolution models presently applied for research and engineering projects.},
  owner = {jaj},
  timestamp = {2013.10.09},
  url = {http://papers.jankowski.org/further-developments-of-untrim-parallel-implementation-and-its-verification},
  }

2001

• Jankowski, J. A., & Zielke, W.. (2001). The mesoscale sediment transport due to technical activities in the deep sea. Deep Sea Research Part II: Topical Studies in Oceanography, 48(17–18), 3487–3521. doi:10.1016/S0967-0645(01)00054-6
  [BibTeX] [Abstract] [Download PDF]
  

  This paper presents a mesoscale model for sediment transport in the deep sea resulting from technical activities such as manganese nodule mining. The model includes the temporal variability of ambient currents, the modification of the water density due to suspended sediments (density driven flow), bottom boundary-layer effects, and the influence of flocculation on the sediment settling velocity. It yields the three-dimensional sediment concentration and the bottom blanketing for time periods of up to a few weeks in areas of up to a few hundred square kilometers. The model also allows simulation of the mobilization, sorption and the transport of heavy metals. Two applications are presented. One treats the sediment transport during the NOAA Benthic Impact Experiment. The other is concerned with dispersion of heavy metals, including the interaction with suspended sediment in the Disturbance and Recolonization Experiment Experimental Area. The model is highly sophisticated with regard to the processes and numerical methods. Nevertheless, a final conclusion concerning the quantification of its prognostic capability for industrial scale operations cannot presently be drawn because of the lack of complete and coherent data sets.

  @Article{Jankowski2001a,
  author = {Jankowski, J.A. and Zielke, W.},
  journal = {Deep Sea Research Part II: Topical Studies in Oceanography},
  title = {The mesoscale sediment transport due to technical activities in the deep sea},
  year = {2001},
  note = {Environmental Impact Studies for the Mining of Polymetallic Nodul es from the Deep Sea},
  number = {17--18},
  pages = {3487--3521},
  volume = {48},
  abstract = {This paper presents a mesoscale model for sediment transport in the deep sea resulting from technical activities such as manganese nodule mining. The model includes the temporal variability of ambient currents, the modification of the water density due to suspended sediments (density driven flow), bottom boundary-layer effects, and the influence of flocculation on the sediment settling velocity. It yields the three-dimensional sediment concentration and the bottom blanketing for time periods of up to a few weeks in areas of up to a few hundred square kilometers. The model also allows simulation of the mobilization, sorption and the transport of heavy metals. Two applications are presented. One treats the sediment transport during the NOAA Benthic Impact Experiment. The other is concerned with dispersion of heavy metals, including the interaction with suspended sediment in the Disturbance and Recolonization Experiment Experimental Area. The model is highly sophisticated with regard to the processes and numerical methods. Nevertheless, a final conclusion concerning the quantification of its prognostic capability for industrial scale operations cannot presently be drawn because of the lack of complete and coherent data sets.},
  doi = {10.1016/S0967-0645(01)00054-6},
  owner = {jaj},
  timestamp = {2013.10.09},
  url = {http://www.sciencedirect.com/science/article/pii/S0967064501000546},
  }

• Oebius, H. U., Becker, H. J., Rolinski, S., & Jankowski, J. A.. (2001). Parametrization and evaluation of marine environmental impacts produced by deep-sea manganese nodule mining. Deep Sea Research Part II: Topical Studies in Oceanography, 48(17–18), 3453–3467. doi:http://dx.doi.org/10.1016/S0967-0645(01)00052-2
  [BibTeX] [Abstract] [Download PDF]
  

  The evaluation of marine environmental impacts resulting from the exploitation of marine resources requires the numerical description, parametrization, and modelling of such processes in order to be able to transfer, compare, and forecast the effects of anthropogenic activities in the deep sea. One of the controversial effects is the formation and behaviour of sediment clouds as a consequence of anthropogenic activities on the seafloor. Since there is a need for reliable data, two subprojects of the “Interdisciplinary Deep-sea Environmental Protection Group (TUSCH)”-project “Impacts from Technical Activities on the Deep-Sea Ecosystem of the South East Pacific Offshore Peru (ATESEPP)” were devoted to the assembly of such data. Based on the German technical approach for deep-sea mining, the possible environmental impacts by a miner were estimated, the impacts on the seafloor were simulated and investigated by tests with large volume undisturbed sediment samples on board the research vessel and in the laboratory, and the results were evaluated and extrapolated. This report gives a comprehensive presentation of the physical problems, the technical approach, and the results of these investigations.

  @Article{Oebius99a,
  author = {Horst U. Oebius and Hermann J. Becker and Susanne Rolinski and Jacek A. Jankowski},
  journal = {Deep Sea Research Part II: Topical Studies in Oceanography},
  title = {Parametrization and evaluation of marine environmental impacts produced by deep-sea manganese nodule mining},
  year = {2001},
  issn = {0967-0645},
  note = {Environmental Impact Studies for the Mining of Polymetallic Nodul es from the Deep Sea},
  number = {17–18},
  pages = {3453--3467},
  volume = {48},
  abstract = {The evaluation of marine environmental impacts resulting from the exploitation of marine resources requires the numerical description,  parametrization, and modelling of such processes in order to be able to transfer, compare, and forecast the effects of anthropogenic activities in the deep sea. One of the controversial effects is the formation and behaviour of sediment clouds as a consequence of anthropogenic activities on the seafloor. Since there is a need for reliable data, two subprojects of the “Interdisciplinary Deep-sea Environmental Protection Group (TUSCH)”-project “Impacts from Technical Activities on the Deep-Sea Ecosystem of the South East Pacific Offshore Peru (ATESEPP)” were devoted to the assembly of such data. Based on the German technical approach for deep-sea mining, the possible environmental impacts by a miner were estimated, the impacts on the seafloor were simulated and investigated by tests with large volume undisturbed sediment samples on board the research vessel and in the laboratory, and the results were evaluated and extrapolated. This report gives a comprehensive presentation of the physical problems, the technical approach, and the results of these investigations.},
  doi = {http://dx.doi.org/10.1016/S0967-0645(01)00052-2},
  url = {http://www.sciencedirect.com/science/article/pii/S0967064501000522},
  }

2000

• Hervouet, J. M., & Jankowski, J. A.. (2000). Comparing numerical simulations of free surface flows using non-hydrostatic Navier-Stokes and Boussinesq equations. Paper presented at the Proceedings of the 4th Conference on Hydroinformatics, Iowa City, Iowa (USA).
  [BibTeX] [Abstract] [Download PDF]
  

  The numerical solutions of three-dimensional, non-hydrostatic Navier-Stokes equations are compared to the ones obtained with Boussinesq equations in the case of a solitary wave in a rectangular channel. The solution procedures used in Telemac-2D for Boussinesq and in Telemac-3D for Navier-Stokes are presented and the numerical results are compared, focusing on the computational time. Depending on the number of mesh levels used in 3D, the solution of full Navier-Stokes equations can be computationally more advantageous than applying the 2D Boussinesq equations.

  @InProceedings{Hervouet2000,
  author = {Hervouet, J. M. and Jankowski, J.A.},
  booktitle = {Proceedings of the 4th Conference on Hydroinformatics},
  title = {Comparing numerical simulations of free surface flows using non-hydrostatic Navier-Stokes and Boussinesq equations},
  year = {2000},
  address = {Iowa City, Iowa (USA)},
  abstract = {The numerical solutions of three-dimensional, non-hydrostatic Navier-Stokes equations are compared to the ones obtained with Boussinesq equations in the case of a solitary wave in a rectangular channel. The solution procedures used in Telemac-2D for Boussinesq and in Telemac-3D for Navier-Stokes are presented and the numerical results are compared, focusing on the computational time. Depending on the number of mesh levels used in 3D, the solution of full Navier-Stokes equations can be computationally more advantageous than applying the 2D Boussinesq equations.},
  owner = {jaj},
  timestamp = {2016.04.17},
  url = {http://papers.jankowski.org/comparing-numerical-simulations-of-free-surface-flows-using-non-hydrostatic-navier-stokes-and-boussinesq-equations},
  }

1999

• Jankowski, J. A.. ((1999). A non-hydrostatic model for free surface flows.). PhD Thesis.
  [BibTeX] [Abstract] [Download PDF]
  

  An algorithm for solution of three-dimensional Navier-Stokes equations for incompressible free surface flows is developed. A decoupled algorithm based on the fractional step (operator-splitting) technique is applied. The solution is obtained in subsequent stages treating equations split into parts having well-defined mathematical properties, so that the most adequate methods for a given differential operator type can be used. The decoupled algorithm structure, which does not use the continuity equation explicitly, allows application of equal-order linear interpolation functions for all variables. The applied reference element type, a prism with six nodes and linear interpolation functions, is a compromise between the exactness of the interpolation, model complexity and computational cost. The finite difference method is applied for the time discretisation and the computational domain variability is taken into account by a standard sigma-mesh structure which is well suited to most geophysical applications. The model is implemented in the framework of the Telemac system, developed in Laboratoire National d’Hydraulique in Chatou, Electricité de France (EDF) for modelling of free surface flows including transport phenomena. It is a far-reaching further development of existing three-dimensional code Telemac-3D whose application domain is limited due to the hydrostatic approximation and because the free surface position is computed from shallow water equations. Therefore, the vertical acceleration is neglected and the free surface and bottom gradients must be small. In the new model, the vertical acceleration is taken into account by decomposing the global pressure into its hydrostatic (i.e. barotropic as well as baroclinic) and hydrodynamic components. In consequence, the hydrodynamic pressure is found from a pressure Poisson equation from fractional formulation, whereby the hydrostatic part is computed explicitly from the free surface elevation and density field. The final velocity is obtained under assumption of its incompressibility from the projection of the intermediate result, which is found without hydrodynamic pressure gradients. The free surface position can be found using height function methods based on the kinematic boundary condition or the free surface conservative equation (vertically integrated continuity equation). In the numerical solution algorithm the method of characteristics, streamline upwind Petrov-Galerkin FEM, or explicit formulation in finite elements can be chosen. The developed new algorithm steps have been verified separately, using analytical solutions. The verification of the algorithm as a whole has been performed using benchmark test cases covering the targeted model application domain. Some of these allowed a formal comparison with an analytical problem solution. They include free surface and internal waves, sub- and supercritical channel flow over a steep ramp, wind- and buoyancy-driven currents. The implementation of the model within the well-validated Telemac system allows immediate application of the newly developed algorithm for practical hydraulic engineering problems and geophysical flows.

  @PhdThesis{Jankowski98D,
  author = {Jankowski, J.A.},
  school = {Universität Hannover},
  title = {{A non-hydrostatic model for free surface flows}},
  year = {1999},
  note = {Bericht Nr. 56/1999, Institut für Strömungsmechanik und ERiB},
  abstract = {An algorithm for solution of three-dimensional Navier-Stokes equations for incompressible free surface flows is developed. A decoupled algorithm based on the fractional step (operator-splitting) technique is applied. The solution is obtained in subsequent stages treating equations split into parts having well-defined mathematical properties, so that the most adequate methods for a given differential operator type can be used. The decoupled algorithm structure, which does not use the continuity equation explicitly, allows application of equal-order linear interpolation functions for all variables. The applied reference element type, a prism with six nodes and linear interpolation functions, is a compromise between the exactness of the interpolation, model complexity and computational cost. The finite difference method is applied for the time discretisation and the computational domain variability is taken into account by a standard sigma-mesh structure which is well suited to most geophysical applications.
  The model is implemented in the framework of the Telemac system, developed in Laboratoire National d’Hydraulique in Chatou, Electricité de France (EDF) for modelling of free surface flows including transport phenomena. It is a far-reaching further development of existing three-dimensional code Telemac-3D whose application domain is limited due to the hydrostatic approximation and because the free surface position is computed from shallow water equations. Therefore, the vertical acceleration is neglected and the free surface and bottom gradients must be small.
  In the new model, the vertical acceleration is taken into account by decomposing the global pressure into its hydrostatic (i.e. barotropic as well as baroclinic) and hydrodynamic components. In consequence, the hydrodynamic pressure is found from a pressure Poisson equation from fractional formulation, whereby the hydrostatic part is computed explicitly from the free surface elevation and density field. The final velocity is obtained under assumption of its incompressibility from the projection of the intermediate result, which is found without hydrodynamic pressure gradients.
  The free surface position can be found using height function methods based on the kinematic boundary condition or the free surface conservative equation (vertically integrated continuity equation). In the numerical solution algorithm the method of characteristics, streamline upwind Petrov-Galerkin FEM, or explicit formulation in finite elements can be chosen.
  The developed new algorithm steps have been verified separately, using analytical solutions. The verification of the algorithm as a whole has been performed using benchmark test cases covering the targeted model application domain. Some of these allowed a formal comparison with an analytical problem solution. They include free surface and internal waves, sub- and supercritical channel flow over a steep ramp, wind- and buoyancy-driven currents.
  The implementation of the model within the well-validated Telemac system allows immediate application of the newly developed algorithm for practical hydraulic engineering problems and geophysical flows.},
  file = {:http\://papers.jankowski.org/wp-content/uploads/d.pdf:PDF},
  url = {http://papers.jankowski.org/a-non-hydrostatic-model-for-free-surface-flows},
  }

• Weilbeer, H., & Jankowski, J. A.. (1999). A Three-Dimensional Non-Hydrostatic Model for Free Surface Flows: Development, Verification and Limitations. Paper presented at the Proceedings of the 6th International Conference on Estuarine and Coastal Modeling, New Orleans, Louisiana, United States.
  [BibTeX] [Abstract] [Download PDF]
  

  The theoretical background of a new finite-element non-hydrostatic model for simulation of free surface flows based on the fractional step method and pressure decomposition is presented. One of the verification cases concerning the solitary wave propagation is provided. Further developments concerning more sophisticated turbulence modelling for practical applications as flows around structures or scour formation are discussed and illustrated with preliminary, but very promising results.

  @InProceedings{Weilbeer1999,
  author = {H. Weilbeer and J. A. Jankowski},
  booktitle = {Proceedings of the 6th International Conference on Estuarine and Coastal Modeling},
  title = {A Three-Dimensional Non-Hydrostatic Model for Free Surface Flows: Development, Verification and Limitations},
  year = {1999},
  address = {New Orleans, Louisiana, United States},
  editor = {Malcolm L. Spaulding and H. Lee Butler},
  month = {November 3--5},
  organization = {ASCE, American Society of Civil Engineers},
  pages = {162--177},
  publisher = {ASCE},
  abstract = {The theoretical background of a new finite-element non-hydrostatic model for simulation of free surface flows based on the fractional step method and pressure decomposition is presented. One of the verification cases concerning the solitary wave propagation is provided. Further developments concerning more sophisticated turbulence modelling for practical applications as flows around structures or scour formation are discussed and illustrated with preliminary, but very promising results.},
  file = {:http\://papers.jankowski.org/wp-content/uploads/weilbeer_jankowski_zielke_1999.pdf:PDF},
  keywords = {Water flow; Free surfaces; Three-dimensional models; Finite element method; Turbulence},
  owner = {jaj},
  timestamp = {2013.10.09},
  url = {http://papers.jankowski.org/a-threedimensional-non-hydrostatic-model-for-free-surface-flows-development-verification-and-limitations},
  }

1997

• Jankowski, J. A., & Zielke, W.. (1997). Data support for modelling of deep-sea mining impacts. Paper presented at the Proceedings of the Seventh (1997) International Offshore and Polar Engineering Confrence, Honolulu, USA.
  [BibTeX] [Abstract] [Download PDF]
  

  The paper critically reviews the presently available experimental data from various tests and experiments connected with the deepsea mining issue with regard to their feasibility in supporting and validating the developed numerical models. Numerical modelling is applied mainly to predetermining the plume development and sea floor blanketing caused by various sediment discharges. The paper describes processes included in these models and discusses the experimental acquisition of needed model parameters. The existing models and their validation are shortly reviewed and parameters essential to operate and validate them are pointed out. Recommendations for further field studies are given in order to improve the quality of model forecasts.

  @InProceedings{Jankowski97,
  author = {Jankowski, J.A. and Zielke, W.},
  booktitle = {Proceedings of the Seventh (1997) International Offshore and Polar Engineering Confrence, Honolulu, USA},
  title = {Data support for modelling of deep-sea mining impacts},
  year = {1997},
  pages = {451--460},
  publisher = {International Society of Offshore and Polar Engineers},
  volume = {I},
  abstract = {The paper critically reviews the presently available experimental data from various tests and experiments connected with the deepsea mining issue with regard to their feasibility in supporting and validating the developed numerical models. Numerical modelling is applied mainly to predetermining the plume development and sea floor blanketing caused by various sediment discharges. The paper describes processes included in these models and discusses the experimental acquisition of needed model parameters. The existing models and their validation are shortly reviewed and parameters essential to operate and validate them are pointed out. Recommendations for further field studies are given in order to improve the quality of model forecasts.},
  url = {http://papers.jankowski.org/data-support-for-modelling-of-deep-sea-mining-impacts},
  }

1996

• Jankowski, J. A., Malcherek, A., & Zielke, W.. (1996). Numerical modeling of suspended sediment due to deep-sea mining. Journal of Geophysical Research: Oceans, 101(C2), 3545–3560. doi:10.1029/95JC03564
  [BibTeX] [Abstract] [Download PDF]
  

  A numerical model was developed in order to estimate the residence time of a sediment plume generated by potential deep-sea mining activities, with special attention to discharges in the bottom boundary layer. The site of the Disturbance and Recolonization Experiment (DISCOL) in the Peru Basin in the southeast Pacific Ocean was chosen as a case study. The model includes the actual bathymetry, as well as the characteristic flow patterns of this region. Various aspects affecting the transport and sedimentation of the plume, such as stratification, flocculation in a sediment-laden water column, and the hydrodynamics are discussed in conjunction with field data and studied with the overall aim of providing a reliable risk assessment of deep-sea mining environmental impacts.

  @Article{Jankowski95a,
  author = {Jankowski, J.A. and Malcherek, A. and Zielke, W.},
  journal = {Journal of Geophysical Research: Oceans},
  title = {Numerical modeling of suspended sediment due to deep-sea mining},
  year = {1996},
  issn = {2156-2202},
  number = {C2},
  pages = {3545--3560},
  volume = {101},
  abstract = {A numerical model was developed in order to estimate the residence time of a sediment plume generated by potential deep-sea mining activities, with special attention to discharges in the bottom boundary layer. The site of the Disturbance and Recolonization Experiment (DISCOL) in the Peru Basin in the southeast Pacific Ocean was chosen as a case study. The model includes the actual bathymetry, as well as the characteristic flow patterns of this region. Various aspects affecting the transport and sedimentation of the plume, such as stratification, flocculation in a sediment-laden water column, and the hydrodynamics are discussed in conjunction with field data and studied with the overall aim of providing a reliable risk assessment of deep-sea mining environmental impacts.},
  doi = {10.1029/95JC03564},
  url = {http://papers.jankowski.org/numerical-modeling-of-suspended-sediment-due-to-deep-sea-mining},
  }

1995

• Jankowski, J. A., & Zielke, W.. (1995). Mesoskalige Stofftransporte im Pazifik als Folge des Tiefseebergbaus (Final Report). Institut für Strömungsmechanik und ERiB, Universität Hannover.
  [BibTeX] [Download PDF]

  @TECHREPORT{Jankowski95,
  author = {Jankowski, J.A. and Zielke, W.},
  title = {{Mesoskalige Stofftransporte im Pazifik als Folge des Tiefseebergbaus}},
  institution = {Institut für Strömungsmechanik und ERiB, Universität Hannover},
  year = {1995},
  type = {Final Report},
  note = {86 pp.},
  url = {http://papers.jankowski.org/mesoskalige-stofftransporte-im-pazifik-als-folge-des-tiefseebergbaus}
  }

• Zielke, W., Jankowski, J. A., Sündermann, J., & Segschneider, J.. (1995). Numerical Modelling of Sediment Transport Caused by Deep Sea Mining. Paper presented at the Proceedings of the First (1995) ISOPE – Ocean Mining Symposium, Tsukuba, Japan.
  [BibTeX] [Abstract] [Download PDF]
  

  The paper describes the application of mesoscale and large scale models in order to simulate the impact of deep sea mining sediment discharges on the marine environment. The modelling efforts are crosslinked with the experiments of the Tusch research group which provide supporting data. The results yield time-dependent and three-dimensional concentration fields, the amount of redeposition, and the plume residence time. The emissions at the bottom lead to an impact mainly at a local scale, whereas contamination in the larger areas due to discharges at the free surface or in some intermediate depth cannot be excluded.

  @InProceedings{Zielke1995,
  author = {Zielke, W. and Jankowski, J.A. and Sündermann, J. and Segschneider, J.},
  booktitle = {Proceedings of the First (1995) ISOPE - Ocean Mining Symposium},
  title = {Numerical Modelling of Sediment Transport Caused by Deep Sea Mining},
  year = {1995},
  address = {Tsukuba, Japan},
  month = {November 21--22},
  pages = {157--161},
  publisher = {ISOPE},
  abstract = {The paper describes the application of mesoscale and large scale models in order to simulate the impact of deep sea mining sediment discharges on the marine environment. The modelling efforts are crosslinked with the experiments of the Tusch research group which provide supporting data. The results yield time-dependent and three-dimensional concentration fields, the amount of redeposition, and the plume residence time. The emissions at the bottom lead to an impact mainly at a local scale, whereas contamination in the larger areas due to discharges at the free surface or in some intermediate depth cannot be excluded.},
  owner = {jaj},
  timestamp = {2013.10.09},
  url = {http://papers.jankowski.org/numerical-modelling-of-sediment-transport-caused-by-deep-sea-mining},
  }

1994

• Jankowski, J. A., Malcherek, A., & Zielke, W.. (1994). Numerical modeling of sediment transport processes caused by deep sea mining discharges. Paper presented at the Proceedings of the OCEANS 94 Conference, Brest.
  [BibTeX] [Abstract] [Download PDF]
  

  A numerical model was developed in order to estimate the residence time of a sediment plume generated by deep-sea mining activities. The model is capable of simulating density currents in a sediment-laden ocean bottom boundary layer. The numerical model was verified using an analytical solution, which does not take into account the above menioned effects. The results show that due to density differences the residence time of a plume is reduced substantially.

  @InProceedings{Jankowski94b,
  author = {Jankowski, J.A. and Malcherek, A. and Zielke, W.},
  booktitle = {Proceedings of the OCEANS 94 Conference, Brest},
  title = {Numerical modeling of sediment transport processes caused by deep sea mining discharges},
  year = {1994},
  pages = {269--276},
  publisher = {IEEE/SEE},
  volume = {III},
  abstract = {A numerical model was developed in order to estimate the residence time of a sediment plume generated by deep-sea mining activities. The model is capable of simulating density currents in a sediment-laden ocean bottom boundary layer. The numerical model was verified using an analytical solution, which does not take into account the above menioned effects. The results show that due to density differences the residence time of a plume is reduced substantially.},
  url = {http://papers.jankowski.org/numerical-modeling-of-sediment-transport-processes-caused-by-deep-sea-mining-discharges},
  }

• Jankowski, J. A., & Zielke, W.. (1994). Mesoskalige Stofftransporte im Pazifik als Folge des Tiefseebergbaus (Report). Institut für Strömungsmechanik und ERiB, Universität Hannover.
  [BibTeX] [Download PDF]

  @TECHREPORT{Jankowski94,
  author = {Jankowski, J.A. and Zielke, W.},
  title = {{Mesoskalige Stofftransporte im Pazifik als Folge des Tiefseebergbaus}},
  institution = {Institut für Strömungsmechanik und ERiB, Universität Hannover},
  year = {1994},
  type = {Report},
  note = {Bericht Nr. JJ/01/1994, 66 pp.},
  url = {http://papers.jankowski.org/mesoskalige-stofftransporte-im-pazifik-als-folge-des-tiefseebergbaus}
  }

1993

• Jankowski, J. A., & Zielke, W.. (1993). Mesoskalige Stofftransporte im Pazifik als Folge des Tiefseebergbaus (Report). Institut für Strömungsmechanik und ERiB, Universität Hannover.
  [BibTeX] [Download PDF]

  @TECHREPORT{Jankowski93,
  author = {Jankowski, J.A. and Zielke, W.},
  title = {{Mesoskalige Stofftransporte im Pazifik als Folge des Tiefseebergbaus}},
  institution = {Institut für Strömungsmechanik und ERiB, Universität Hannover},
  year = {1993},
  type = {Report},
  note = {Bericht Nr. JJ/01/1993, 136 pp.},
  url = {http://papers.jankowski.org/mesoskalige-stofftransporte-im-pazifik-als-folge-des-tiefseebergbaus}
  }

1992

• Malcherek, A., Jankowski, J. A., & Hoyme, H.. (1992). SEACLOUD: Ein analytisches Modell zur Berechnung des mesoskaligen Stofftransports als Folge des Tiefseebergbaus (Report). Institut für Strömungsmechanik und ERiB, Universität Hannover.
  [BibTeX]

  @TECHREPORT{Malcherek92S,
  author = {Malcherek, A. and Jankowski, J.A. and Hoyme, H.},
  title = {{SEACLOUD: Ein analytisches Modell zur Berechnung des mesoskaligen
  Stofftransports als Folge des Tiefseebergbaus}},
  institution = {Institut für Strömungsmechanik und ERiB, Universität Hannover},
  year = {1992},
  type = {Report},
  note = {(Bericht Nr. AM/003/1992), 144 pp.}
  }