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Old   January 27, 2008, 16:18
Default Solver Selection with COMSOL
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S. Gatzka
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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!
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Old   January 27, 2008, 17:35
Default Re: Solver Selection with COMSOL
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S. Gatzka
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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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