[Sebastian.]

Hey,

i am relatively new to OpenFoam, but i successfully did some cases with the incompressibleFlow SolverModule and incompressible flows with the fluid SolverModule. I am working with OF11, so the .org-version. Now i am trying to run a laminar compressible flow in a easy straight-pipe geometry with the perfectGas-model, but i just cant get a case running. I searched through the tutorials and also the template-files for a CHT case, but i do not get, what to do .

So now my questions: and i guess they connected
- there are several discritisation schemes that i found:
div(phi(p|rho)
div(phid,p)
div((phi|interpolate(rho)),p)
Which one of these do i need and whats the difference (i read smth. about Ma-number) between them.
- when do i use a solver for p and when for p_rgh? and for what do i have to whatch out for when i set their initial values?
- I add the most important files from my template case with rhoConst. What do i have to change?

Help would be much appreciated. Or maybe just some hint where to find the information. I searched the web, the user guide, several tutorials but i am completly stuck

Here the files, because upload make troubles:

0/p_rgh

  dimensions [ 1 -1 -2 0 0 0 0 ];
  
  internalField uniform 0;
  
  boundaryField 
  {
      inlet
      {
          type            fixedFluxPressure;
      }
  
      outlet
      {
          type            fixedValue;
          value           uniform 0;
      }
  
      wand
      {
          type            fixedFluxPressure;
      }
  }

0/p

  dimensions      [ 1 -1 -2 0 0 0 0 ];
  
  internalField   uniform 1e05;
  
  boundaryField
  {
      ".*"
      {
          type            calculated;
          value           uniform 0;
      }
  }

constant/physicalProperties

  // AIR @ T = 293 K = 20 °C
  
  thermoType
  {
      type            heRhoThermo;
      mixture         pureMixture;
      transport       const;
      thermo          hConst;
      equationOfState perfectGas;
      specie          specie;
      energy          sensibleEnthalpy;
  }
  
  mixture
  {
      specie
      {
          nMoles      1;
          molWeight   28.9;           // [g/mol]
      }
      thermodynamics
      {
          Cp          1006;           // [J/kg*K]
          Hf          0;
      }
      transport
      {
          mu          1.81e-05;       // [Pa*s]
          Pr          0.71;
      }
  }

system/fvSchemes

  ddtSchemes
  {
      default         steadyState;
  }
  
  gradSchemes
  {
      default         Gauss linear;
  }
  
  divSchemes
  {
      default         none;
  
      div(phi,e)          Gauss linearUpwind grad(U);
      div(phi,U)          Gauss linearUpwind grad(U);
      div(phi,(p|rho))    Gauss linear;
      div(phi,K)          Gauss linear;
  
  }
  
  laplacianSchemes
  {
      default         Gauss linear corrected;
  }
  
  interpolationSchemes
  {
      default         linear;
  }
  
  snGradSchemes
  {
      default         corrected;
  }

system/fvSolution

  solvers
  {
      U
      {
          solver           PBiCGStab;
          preconditioner   DILU;
          tolerance        1e-6;
          relTol           0.1;
      }
  
      e
      {
          solver           PBiCGStab;
          preconditioner   DILU;
          tolerance        1e-6;
          relTol           0.1;
      }
  
      p_rgh
      {
          solver           GAMG;
          smoother         GaussSeidel;
          tolerance        1e-7;
          relTol           0.01;
          //minIter          3;
          maxIter          100;
      }
  }
  
  PIMPLE
  {
      momentumPredictor           yes;
      nCorrectors                 1;
      nNonOrthogonalCorrectors    1;
  }
  
  relaxationFactors
  {
      fields
      {
          p_rgh           0.3;
      }
      equations
      {
          U               0.7;
          ".*"            0.7;
      }
  }