[acouteau]

Dear OpenFOAM users,


I am trying to run simulations of a gas tank filling and study the heat transfer from the gas to the wall using chtMultiRegionFoam. The tank is cylindrical and I have created a mesh using a cylindrically shape blockMesh then refined it using snappyHexMesh.

However, I run into oscillations towards the end of the tank, as can be seen on the temperature pictures. These also results in extracted wallHeatFlux oscillations, as can be seen on the wall heat flux picture from paraview and on the graph showing heat flux along x at different angles.


I see 3 possibilities for these oscillations:

• The mesh: better refinement towards the end of the tank and/or more progressive grading should help. However, I believe the mesh looks good enough (grading-wise) and the velocity are anyway much smaller at the end of the end than in the jet region.
• The solvers: I use the following fvSchemes for the fluid region
  

  ddtSchemes
  {
      default         Euler;
  }
  
  gradSchemes
  {
      default         Gauss linear;
  }
  
  divSchemes
  {
      default         none;
  
      div(phi,U)      Gauss upwind;
  
      div(phi,K)      Gauss linear;
      div(phi,h)      Gauss upwind;
  
      div(phi,k)      Gauss upwind;
      div(phi,epsilon) Gauss upwind;
      div(phi,omega)  Gauss upwind;
  
      div(phi,R)      Gauss upwind;
      div((rho*R))    Gauss linear;
      div(R)          Gauss linear;
      div(U)          Gauss linear;
  
      div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear;
  }
  
  laplacianSchemes
  {
      default         Gauss linear corrected;
  }
  
  interpolationSchemes
  {
      default         linear;
  }
  
  snGradSchemes
  {
      default         corrected;
  }
  
  wallDist
  {
      method          meshWave;
  }

  that I inherited from the previous person working on this project. I am not an expert in choosing the schemes, so if someone picks up one that possibly leads to oscillations/checkerboard patterns, that'd be helpful!
• The gas-solid boundary condition:
  I use noSlip for velocity and the recommended for temperature:
  

          gas_to_liner
          {
              type           compressible::turbulentTemperatureRadCoupledMixed;
              Tnbr            T;
              kappaMethod     fluidThermo;
              value           uniform 288.15;
          }

Closing points:

• I use OF-v2206
• I use kOmegaSST turbulence model
• The time step is very small due to CFL limitations in the inlet pipe, and sadly, no (supported) local time stepping yet in CHT. So I'm ruling out issues with time step size

I thank you all in advance!
Arthur