Regarding modified drag force formulation for application in dense flows

轉載自：http://www.cfd-online.com/Forums/openfoam-programming-development/129966-regarding-modified-drag-force-formulation-application-dense-flows.html

If you have a look into the classes defined in the folder "src/lagrangian/intermediate/submodels/Kinematic/ParticleForces", there is an interesting pattern:

• The sub-folder "ParticleForce" has the base class for all possible forces. It has 3 important methods:

  Code:

• //- Calculate the coupled force
              virtual forceSuSp calcCoupled
              (
                  const typename CloudType::parcelType& p,
                  const scalar dt,
                  const scalar mass,
                  const scalar Re,
                  const scalar muc
              ) const;
  
              //- Calculate the non-coupled force
              virtual forceSuSp calcNonCoupled
              (
                  const typename CloudType::parcelType& p,
                  const scalar dt,
                  const scalar mass,
                  const scalar Re,
                  const scalar muc
              ) const;
  
              //- Return the added mass
              virtual scalar massAdd
              (
                  const typename CloudType::parcelType& p,
                  const scalar mass
              ) const;      

• • All rely in the class "forceSuSp", located in the sub-folder of the same name, which has the following description:

    Quote:

    Code: Helper container for force Su and Sp terms. F = Sp(U - Up) + Su Explicit contribution, Su specified as a force Implicit coefficient, Sp specified as force/velocity

  • For example, the sub-folder "Lift/LiftForce" has the base class structure for lift, which relies in the method "calcCoupled" and defines only the "Su" part and "Sp" is set to "0.0".
  • The sub-folder "Drag" has the classes for drag, from which you've pointed out "SphereDrag". These classes also rely in the method "calcCoupled" and defines only the "Sp" part.
  • The sub-folder "Gravity" has a single class that relies in the method "calcNonCoupled" and affects only "Su".
  • The class in the sub-folder "PressureGradient" also relies in the method "calcCoupled" and also affects "Su" only.

  OK, so this gets us the individual accountabilities of each force component. The remaining question is: how are all of them added up?

  It's in the class "KinematicParcel", method "calcVelocity", located in the folder "src/lagrangian/intermediate/parcels/Templates/KinematicParcel/". It relies on the class "TrackData::cloudType::forceType", where "TrackData" is a template name... OK, I got lost here, because this section is deeply based in templates, which is a considerable pain to figure out who-is-what-and-where-and-how 

  

  But the point is that this line:

  Code:

  const forceSuSp Fcp = forces.calcCoupled(p, dt, mass, Re, mu);      

  is probably the addition of all forces that is listed inside "forces".

• Hi ansu, Bruno,

  I am also investigating this solver. I still have many remaining questions, but maybe the follwing gives you a starting point:

  A. For information on template for class Trackdata look into /intermediate/parcels/Templates/KinematicParcel/KinematicParcel.C.

  B. If you want to include a new force to the solver, you may try the following (which I haven't tried yet):

  • Copy the intermediate library, recompile it to something like "mylib" in your user folder and link the new user library to your own copy of the solver (myIco... )
  • in submodels/Kinematic/ParticleForces/.. copy a drag model and rename it (do not forget to rename the classes inside the file)

  • In intermediate/parcels/include/makeParcelForces.H include the file "myNewForce.H" and add the force to the definition (register it to the library):

    Code:

    ...
    #include "myNewForce.H"
    
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    
    #define makeParcelForces(CloudType)                                           \
                                                                                  \
        makeParticleForceModel(CloudType);                                        \
        makeParticleForceModelType(myNewForce, CloudType);                   \
    ...      

  • In the case file /constant/kinematicCloudProperties add

    Code:

    ...
    subModels
    {
        particleForces
        {
            sphereDrag;
            gravity;
            myNewForce;
        }
    ...      

  I might find some time at the weekend to implement a new force and check if the works. I will keep you updated.