Question #143963 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/143963
Status: Open => Answered
Andre Massing proposed the following answer:
Den 03.02.11 17.37, skrev Till B:
> 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
>
To remedy the issues with a direct solver you can change to an iterative
solver which is by far less memory consuming.
Have a look at the parameter demos or the stokes-iterative demos
in the undocumented demo section in your dolfin installation.
Cheers,
Andre
--
André Massing email: [email protected]
Ph.D. student mobile: +47 469 57 401
Simula Research Laboratory
NO-1367 Fornebu, Norway
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