I am using COMSOL for modelling the movement of the surface water. Figures are attached. My input data is in the form of topographic points, with X, Y and Z, and I am using 2D modelling (figure 1). The geometry is a square with the size of 6000 in 6000 meters. I also introduce a river to the geometry by defining the points of the river (figure 2). The only type of meshing that models the topography correctly is the mapped meshing with fixed distribution of elements. As I use other meshing techniques, the simulation shows water on the surface of the ground even if I consider the source term equal to zero (figure 3, the picture shows running the model with source term of zero). The problem of using mapped mesh in my case is that I cannot define an inner boundary (i.e. a stream) in the geometry. What do you recommend me to do so that I can use a meshing in my model, without having the problem of showing water on the surface even if the source term is zero?
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