I am using ASPECT 2.3.0 to simulate crustal deformation in 3D in presence of compression and extension, and for some of my simulations I would like to introduce erosion. As pointed out in the manual, erosion is reproduced by diffusing the surface, and the diffusion rate depends on a hillslope transport coefficient k that has a default value of 10e-6.
I have already run my models by adopting a free surface, and everything works as expected. However, when I switch from free surface to diffusion, I always obtain a flat model surface, regardless of the adopted value for k (I tested values ranging from 10e-4 to 10e-30). In addition, when I implement time dependent, compression-to-extension velocity boundary conditions, the solver does not converge anymore when the change of velocity at the boundaries occurs.
Can anyone tell me a little bit more about how the surface diffusion works, and why I do not see any relief in the model surface?
Thank you very much.