# Solver Selection with COMSOL

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 January 27, 2008, 16:18 Solver Selection with COMSOL #1 S. Gatzka Guest   Posts: n/a Hello World. Another Problem with COMSOL. Problem Geometry is just a square. Its a problem with natural convection. So I created a multiphysical model: Non-isothermal flow and general heat transfer. The problem has two adiabat boundary conditions at the top and at the bottom. On the boundarys to the right and to the left I created temperature-conditions. The left wall is 100 K hotter than the other. Concerning the flow there are 4 similar conditons: no-slip (u=v=0) on all boundarys. Thermal conductivity and heat capacity were chosen with constants. For the density I created a subdomain expression which is equal to the Boussinesq-approximation (rho=rho0(1-beta(T-T0)). To create the gravitational force I declared the volume-force (Fy) with -g*rho0. I used Lagrange Quadratic Elements. But I cant get a solution using the Stationary Nonlinear Solver: Failed to find a solution: No convergence, even when using the minimum damping factor. Returned solution has not converged. What is the problem? Problem set is located here: http://rapidshare.com/files/87111315...elter.mph.html Thanks in advance!

 January 27, 2008, 17:35 Re: Solver Selection with COMSOL #2 S. Gatzka Guest   Posts: n/a I simulated the problem with FLUENT. On first impression it seems to work. In materials I declared the boussinesq approximation. But still I have to specify a density. When solving the problem I get a contour of Stream Function that looks like the one I have from a reverence solution. But when I display the density it is constant all over the area. But how is that? It has to follow the boussinesq law? Case, Data and Mesh are stored here: http://rapidshare.com/files/87129064/square.rar.html

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