open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,

I have a channel with complex bathymetry. I notice that as I increase the number of horizontal layers the free surface becomes increasingly less responsive to changes in the roughness coefficient. As the number of layers approaches 30 the model becomes too insensitive.

I thought that the roughness height shouldn't be affected by the number of layers. However, changing the number of horizontal layers is the only parameter which seems to influence the sensitivity issue (I've tested mesh improvements, solvers, free surface boundary conditions,added more diffusion,..).

Would it be correct to say that the increased vertical resolution means that the model is taking into account more bathymetry i.e. the model is resolving more vertical structure in the fluid flow which dampens the effect of bed roughness.

Would appreciate any advice on this matter.

Many thanks and kind regards.