RELATIONSHIP BETWEEN THE HYDRODYNAMICS IN THE MELT AND THE SHAPE OF THE CRYSTAL MELT INTERFACE DURING CZOCHRALSKI GROWTH OF OXIDE SINGLE-CRYSTALS .2. DETERMINATION OF THE CRITICAL CRYSTAL ROTATION RATE FROM PHYSICAL SIMULATION DATA ON GROWTH IN THE PRESENCE OF SIMULTANEOUS FREE AND FORCED CONVECTIONS - COMPARISON WITH EXPERIMENTAL-DATA ON CRYSTAL-GROWTHT