Flow over a rough bed

This case is a simulation of water flow over gravel in a flume. The experiment was done at the University of Braunschweig in Germany by Dr. Jochen Aberle and Dr. Katinka Koll. Detailed measurements of velocity and turbulence profiles were done for a number of water levels and discharges.

The case was modelled with very fine grid, resolving the roughness elements. Our department carried out a study solving the Reynolds-Averaged Navier-Stokes Equations (RANS). Dr. Thorsten Stoesser at the Georgia Institute of Technology computed the same case with Large Eddy Simulations. Our RANS computations used different grids, the finest with 72 million cells. Details of some of the grids are given below.

The two figures below shows the grid and the velocities in colour. Red is highest velocity and blue is lowest velocity.

Examples of vertical velocity profiles is given below. The measurements were done by a laser instrument. The computations were done by SSIIM 2. Both a first-orde upwind scheme (POW) and a second-order upwind scheme (SOU) were used.

The velocity in m/s is on the horizontal axis and the vertial axis is level above the bed in meters.

The following pictures shows the flume seen from above, where the colours give the values of the different variables close to the bed:

The figure above shows the bed shear stress. Red is 3 Pa and blue is zero.

The research is being carried out in cooparation with Dr. Jochen Aberle and Dr. Katinka Koll at the University of Braunschweig and Dr. Thorsten Stösser at Georgia Institute of Technology.

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This page was last updated: 19. October 2010