Hi Spencer, I also used Zero-Neumann BC on velocity and Zero Dirichlet BC on pressure and got the same result. I simulate this flow using OpenFOAM also, where at outlet boundary I imposed zeroGradient BC on velocity for positive flux (outflow) and zeroValue(Dirichlet) for negative flux (inflow). Could we do similar to this in Nektar++? warm regards, Sartaj Tanweer Research Scholar, Department of Applied Mechanics, Indian Institute of Technology Delhi, India On Sun, Dec 13, 2020 at 5:30 PM Sherwin, Spencer J <s.sherwin@imperial.ac.uk> wrote:

HI Shartaj,

That does indeed look strange. I am cc’ing Mohammad who has been running temperature based simulations. i cannot see anything wrong in your condition file so I wonder if we have an issue on how it is selecting the pressure information in this outflow condition.

Have you tried using the simpler out flow condition of Zero-Neumann on velocity and Zero Dirichlet on pressure. If you get energetic vorticites at the outflow this may cause problems (which is what the HOUTFLOW is good for) but it might get you going for now.

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 20 Nov 2020, at 06:33, Sartaj Tanweer <s.tanweer25@gmail.com> wrote:

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Dear all,

I am using Nektar++(4.4.1) for computations of the flow past a square cylinder placed near a moving wall under the influence of buoyancy. I have used *"HOutflow*" boundary condition at the outlet as suggested by the user guide, but I got the wrong result.

Could someone please suggest a right BC at the outlet?

I have attached the mesh and condition files and the resultant streamlines.

with best regards, Sartaj Tanweer <conditions.xml><streamlines.tiff><mesh.xml> _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users