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[Till B <question143963@xxxxxxxxxxxxxxxxxxxxx>]

New question #143963 on DOLFIN:
https://answers.launchpad.net/dolfin/+question/143963

Hi,

I recently installed the Fenics package and now I try to solve some problems with it. I want to simulate the flow of air around an obstacle. Eventually I want to include the temperature and see how a hot obstacle cools down in a colder air flow. However I encounter several problems, already with my baby example which does not even include the temperature. I am new in the CFD business. To begin, I adapted a few examples for Navier-Stokes solvers that I found in the Dolfin examples or on launchpad.net/nsbench (I tried both steady state and transient flow examples). I use a 3d mesh. 

My main problem occurs with mesh size. Unless I use a rather coarse mesh, I run out of memory, sometimes with a std::bad_alloc error, sometimes with the message that UMFPACK has run out of memory. It works with a mesh that has 7828 cells, but for example not, if I refine this mesh with the refine function of Dolfin. 
Is there anything I can do about this? I could get more RAM, but I do not think that this will ultimately solve my problem. In the end I want to use much larger meshes. 

With this coarse mesh I do not get realistic results. Now matter how I set my inflow velocity, the speed of the fluid in the bulk is very low. When I use a 2d version of my example with a finer mesh, I get results that make sense. 

Is there a way to circumvent the memory issue? 

Thank you!

Till

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