Tag Archives: semi-Lagrangian

Parallel implementation of a non-hydrostatic model for free surface flows with semi-Lagrangian advection treatment

Jacek A. Jankowski

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. Continue reading

Very high resolution numerical modelling for inland waterway design

R. Patzwahl, J.A. Jankowski, T. Lege

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. Continue reading

Verification and validation of the parallel UnTRIM

Jacek A. Jankowski. Verification and validation of the parallel UnTRIM, 5th UnTRIM Workshop, Trento, 19-21 May 2008.

A new UnTRIM version has been released (see Casulli 2008), featuring better data locality, improved interpolations in the advection scheme and, the most important, a radically new mass-conservative iterative approach to drying and wetting treatment based on Newton iterations with a proven convergence. In the presentation, detailed issues detected during the verification and validation of the refreshed MPI-parallel “2009” version of UnTRIM are presented, treated and resolved. Continue reading

Parallel streamline tracking for UnTRIM

Jacek A. Jankowski. Parallel streamline tracking for UnTRIM, 4th UnTRIM Workshop, Trento, 7-9 May 2007.

The parallel streamline tracking algorithm for the domain decomposition method applied in the MPI version of UnTRIM, is described in detail. The streamline tracking is the integral part of the semi-Lagrangian method of characteristics, being one of the most robust methods for the non-linear momentum advection, working also for larger Courant numbers. The method is however awkward to parallelise in the framework of the point-to-point communication typical for the domain decomposition method. Continue reading

UnTRIM parallelization with message passing

Jacek A. Jankowski. UnTRIM parallelization with message passing, 3rd UnTRIM Workshop, Trento, 15-17 May 2006.

This is a second part of the UnTRIM parallelisation project presentations — for the background, see the previous post. The most important issue addressed so far concerns absolving a number of stringent verification tests applied for checking the parallel implementation correctness as well as the user steering of the model. Continue reading