[babakflame]

Dear Folks

I am kinda new in multiphase solvers of OpenFoam. I am trying to learn SmagorinskyZhang model in this address in OF 8.
$FOAM_SRC/MomentumTransportModels/phaseCompressible/LES/SmagorinskyZhang

Can somebody please explain to me what does this if condition exactly mean?

  if (!gasTurbulencePtr_)
     {
         const volVectorField& U = this->U_;
  
         const transportModel& liquid = this->transport();
         const twoPhaseSystem& fluid =
             refCast<const twoPhaseSystem>(liquid.fluid());
         const transportModel& gas = fluid.otherPhase(liquid);
  
         gasTurbulencePtr_ =
            &U.db()
            .lookupObject<PhaseCompressibleTurbulenceModel<transportModel>>
             (
                 IOobject::groupName
                 (
                     turbulenceModel::propertiesName,
                     gas.name()
                 )
             );
     }

Thanks