Possible variable name conflict in friction models for liquid film

Summary

In the liquidFilm model, when computing the wall shear stress with DarcyWeisbach model, the same variable name Cf is used as for the modelling of the shear stress at the liquid/gas interface.

Steps to reproduce

Please refer to the two variable definitions:

• shear stress at the liquid/gas interface in $FOAM_SRC/regionFaModels/liquidFilm/subModels/kinematic/filmTurbulenceModel/laminar/laminar.C
• wall shear stress (solid/liquid film interface) in $FOAM_SRC/regionFaModels/liquidFilm/subModels/kinematic/filmTurbulenceModel/filmTurbulenceModel/filmTurbulenceModel.C

Example case

Please refer to the tutorial $FOAM_TUTORIALS/lagrangian/kinematicParcelFoam/pitzDailyWithSprinkles, with the following modification for 0/U.base:

    laminarCoeffs  
    {  
        friction        DarcyWeisbach; // Wall friction model  
        Cf              0;      // Gas friction or Cf for DarcyWeisbach model  
    }  

What is the current bug behaviour?

The entry Cf seems to be used both for the computation of the gas friction and in the DarcyWeisbach wall friction model.

What is the expected correct behavior?

Change one of the two variable names, either for the gas friction or in the DarcyWeisbach model to avoid the naming conflict.

Relevant logs and/or images

Environment information

• OpenFOAM version : develop
• Operating system : ubuntu
• Compiler : gcc

Possible fixes

Change the name for the variable Cf in the DarcyWeisbach model.