Tag Archives: three-dimensional

Accurate vertical profiles of turbulent flow in z-layer models

F.W. Platzek, G.S. Stelling, J.A. Jankowski and J.D. Pietrzak

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. Continue reading

On the representation of bottom shear stress in z-layer models

F. Platzek, G.S. Stelling, J.A. Jankowski, R. Patzwahl

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. Continue reading

Mathematical Model UnTRIM – MPI Version Manual

Jacek A. Jankowski

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. Continue reading

Further developments of UnTRIM: parallel implementation and its verification

Jacek A. Jankowski. Further developments of UnTRIM: parallel implementation and its verification, ISEH V – IAHR Fifth International Symposium on Environmental Hydraulics, 2007, Tempe, Arizona, USA.

This presentation is complementary to the contributed conference paper. It is a summary of all stages of the development of the parallel version of UnTRIM applying the domain decomposition method and message passing (MPI): Continue reading

Further developments of UnTRIM: parallel implementation and its verification

J.A. Jankowski

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. Continue reading