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Problem with meshing

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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?



2 Replies Last Post 29 ago 2019, 04:58 GMT-4
Michael Rembe Certified Consultant

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Posted: 5 years ago 15 ago 2019, 06:19 GMT-4
Updated: 5 years ago 15 ago 2019, 06:16 GMT-4

Hi Saeed,

I don't fully understand what do you do. Du you want simulate subsurface flow (groundwater) or the (movement) flow of the surface water?

If you want to simulate the flow of surface water it is not so easy. From my point of view you have to set up a 3D model or you have to set up the so called shallow water equations. You can read an example in the blog "Solving Shallow Water Equations with Equation-Based Modeling"

https://www.comsol.com/blogs/solving-shallow-water-equations-with-equation-based-modeling/

I hope it will help you!

Best regards, Michael

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Michael Rembe
Rembe Consulting PartG mbB
www.rembe-consulting.de


Hi Saeed, I don't fully understand what do you do. Du you want simulate subsurface flow (groundwater) or the (movement) flow of the surface water? If you want to simulate the flow of surface water it is not so easy. From my point of view you have to set up a 3D model or you have to set up the so called shallow water equations. You can read an example in the blog "Solving Shallow Water Equations with Equation-Based Modeling" https://www.comsol.com/blogs/solving-shallow-water-equations-with-equation-based-modeling/ I hope it will help you! Best regards, Michael

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Posted: 5 years ago 29 ago 2019, 04:58 GMT-4

Hey Saeed,

Based on what you described this video might also be useful. https://www.comsol.com/video/equation-based-modeling-custom-simulations-comsol-multiphysics If not, a bit more in-depth explanation would be nice.

Regards, Rob

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www.ti-electronic.com/pcbassembly/
Hey Saeed, Based on what you described this video might also be useful. https://www.comsol.com/video/equation-based-modeling-custom-simulations-comsol-multiphysics If not, a bit more in-depth explanation would be nice. Regards, Rob

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