code: def frac_vol_floc(ConcAluminum, ConcClay, coag, DIM_FRACTAL,
                    material, DiamTarget):
      
      return (frac_vol_floc_initial(ConcAluminum, ConcClay, coag, material)
              * (DiamTarget / material.Diameter)**(3-DIM_FRACTAL)
              )
docs: Return the floc volume fraction.