| JBurnham |
December 10, 2013 11:13 |
Hi, Miss Miti. There are several reasons you might be having insufficient scour. Please try the following:
1) check the mesh resolution: there should be at least 4 cells across all solid components, and ideally there should be at least 10 cells across the most shallow flow depth.
2) check the boundary conditions: are the water free-surface elevations correct? if you are using flow rate or velocity, are they correct?
3) calibrate the sediment Critical Shields Parameter. It is best to do this with a 2-D mesh (only one cell in the 3rd direction, make sure the cell is thin so that the geometry in it is also 2-D). Vary the Critical Shields Parameter until the nearly correct scour formation is observed.
4) also in 2-D, if necessary, turn off scour entirely and get the simulation to run correctly for just water. Then turn scour back on. This is a good way to debug simulations that have problems besides the scour model.
5) check units. All your units should be consistent. If you are in SI units, for example, the sediment density should be in kg/m^e (e.g., 2650), and the sediment diameter should be in m (e.g., 0.001 for 1 mm sand).
6) do the tutorials in the User Manual and on the User Site. Consider attending a training for FLOW-3D. Contact the company that sold you the software to get more info about training, or consider asking them for support.
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