The melt flow has a significant effect on the structure developing during the unidirectional solidification of alloys. This phenomenon can be experienced during the solidification of melts stirred by the rotating magnetic field (RMF)-type magnetohydrodynamic (MHD) facility as well. As it would be very difficult to measure the intensity of melt flow (e.g. its revolution number, angular velocity) during solidification, it seems to be reasonable to perform the so-called "scale model" experiments applied usually in the hydrodynamics. Using the results of these measurements, conclusions can be drawn concerning the flows during solidification by means of the similarity law of hydrodynamics. The revolution number of Ga-In alloy melt placed in the rotating magnetic field can be measured by the equipment developed for performing the "scale model" experiments. The measurements were performed in crucibles with different surface roughness using melt-cylinders with different diameters located in rotating magnetic field having different frequencies and magnetic induction.