On 15 Sep 2020, at 10:33, Edward Threlfall <ejthrelfall@gmail.com> wrote:

Dear Professor,

You are correct, the example is supposed to be Rayleigh-Benard convection in a 3D box (a temperature-driven flow).  Prof. Hossain provided me with a working 2D example and I tried to convert to 3D.

I am now trying to get Nektar++ running in the Visual Studio IDE so I can attempt to find the issue.

Many thanks,

Ed.

On Tue, Sep 15, 2020 at 10:16 AM Sherwin, Spencer J <s.sherwin@imperial.ac.uk> wrote:

Hi Ed,

Having a quick look at your file  it seems the problem might be something like a temperature  driven flow in a box? Adding a temperature field like this might be the issue since I would have expected this case to run otherwise. 

Mohammad (cc’ed) has been working on a  branch of the code where we have fixed a number of issues to do with adding a temperature field. @Mohammad: Could you try running Ed’s case and see if it works for you? If so I suggest Ed runs on your branch until we get that merged? 

Cheers,

Spencer.

Spencer Sherwin FREng, FRAeS
Head of Aerodynamics Section,
Director of Research Computing Service,
Professor of Computational Fluid Mechanics,
Department of Aeronautics,
South Kensington Campus,

Imperial College London, SW7 2AZ,  UK
Phone: +44 (0)20 7594 5052

http://www.imperial.ac.uk/people/s.sherwin/

On 10 Sep 2020, at 18:04, Edward Threlfall <ejthrelfall@gmail.com> wrote:

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Dear users,

I have been running simulations of 3D convection in a box with the incompressible Navier-Stokes solver.

I find that there is always an anomaly at one of the points, where the pressure field is zero (it is obvious that this zero value is wrong - see attached image).  It might be worth noting that in the image, there are 12 elements with 4 modes per direction each, so 12*4^3 (=768) degrees of freedom, and the anomalous point seems to be number 767 i.e. the final one, so perhaps the last pressure variable is not being updated.  The session file used to generate the result shown in the image is attached (takes about 1min to run on my laptop).  Also note it is correct that u, v, w, and T are zero at the sample point - just not p!

I have found this issue on a variety of cuboidal and also tetrahedral meshes.

The command to run I used is

mpiexec -np 4 incnavierstokessolver nektar_3d_convection.xml

Can anyone help resolve this?

Many thanks,

Dr Ed Threlfall, UKAEA.

<nektar_3d_convection_problem.png><nektar_3d_convection.xml>_______________________________________________
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