telemac3d-gaia/bed exchange reference height incompatibility
It is a fairly well known fact that the vertical discretisation of telemac3d affects the net erosion and deposition patterns. This is because there is an imbalance between the erosion (which uses a fixed reference height for determining the reference concentration) and the deposition (which uses the concentration in plane 1, which is not representative of the concentration at the reference height used for erosion).
I have obtained better results by extrapolating the deposition concentration down to the same height as the reference concentration height. This is somewhat complicated because the height of plane 1 is not obvious! (and may vary in definition between different vertical schemes). However, for the "set_dif" scheme, using an assumed height of 1/4 of the distance between plane1 and plane2 as the height of the concentration leads to much improved results when comparing with 2D and there is considerably less variability in bed evolution when the plane discretisation is changed. It is likely that there is a better definition for the height of plane 1 concentration...I am working on it, but if anyone else has suggestions then they are welcome!
I have attached a powerpoint that I hope demonstrates the improvements. csratio.pptx
cheers Tom