populationBalanceModel → velocityGroup Relation

File in applications/solvers/multiphase/multiphaseEulerFoam/phaseSystems/populationBalanceModel	Includes file in applications/solvers/multiphase/multiphaseEulerFoam/phaseSystems/diameterModels/velocityGroup
populationBalanceModel / populationBalanceModel.H	sizeGroup / sizeGroup.H