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IDProjectCategoryView StatusLast Update
0000054OpenFOAM[All Projects] Bugpublic2010-10-07 17:58
Reporteruser50Assigned Tohenry 
PriorityhighSeveritymajorReproducibilityalways
Status resolvedResolutionfixed 
Product Version 
Fixed in Version 
Summary0000054: The buoyancy force term in the momentum equation of the buoyantBoussinesqPimpleFoam solver is incorrect.
DescriptionIn OF 1.6.x (buoyantBoussinesqPisoFoam) the buoyancy force term in Ueqn.h is

  UEqn
   ==
  fvc::reconstruct
  (
     (
    fvc::interpolate(rhok)*(g & mesh.Sf()) <===
        - fvc::snGrad(p)*mesh.magSf()
     )
  )

This changed in OF 1.7.x (buoyandBoussinesqPimpleFoam) to

  UEqn
   ==
  fvc::reconstruct
  (
     (
    - ghf*fvc::snGrad(rhok)*mesh.magSf() <===
        - fvc::snGrad(p)*mesh.magSf()
     )
  )

which is incorrect. The buoyancy force should be F=rhok*g instead of F~grad(T)*g.h
Additional InformationIn my calculations (Rayleigh-Benard configuration) the UZ residual practically does not drop with increasing number of pimple iterations. Changing back to the buoyancy force term from OF 1.6.x solves this problem.

As far as I see, also the other solvers in heatTransfer are affected.
TagsModelling, Solver

Activities

henry

2010-10-07 10:57

manager   ~0000077

This is already fixed in OpenFOAM-1.7.x, the error is in using p rather than p_rgh. The correct form of the momentum predictor is

        solve
        (
            UEqn
         ==
            fvc::reconstruct
            (
                (
                  - ghf*fvc::snGrad(rhok)
                  - fvc::snGrad(p_rgh)
                )*mesh.magSf()
            ),
            mesh.solver(U.select(finalIter))
        );

Issue History

Date Modified Username Field Change
2010-10-07 10:42 user50 New Issue
2010-10-07 10:52 henry Assigned To => henry
2010-10-07 10:52 henry Status new => assigned
2010-10-07 10:57 henry Note Added: 0000077
2010-10-07 10:57 henry Status assigned => resolved
2010-10-07 10:57 henry Resolution open => fixed
2010-10-07 17:58 user2 Tag Attached: Modelling
2010-10-07 17:58 user2 Tag Attached: Solver