Determination of Laminar/Turbulent Flow Transition Using Pressure Compensation Method for Ga75In25 Alloy Stirred by RMF

Melt flow has a very significant influence on the microstructure formed during solidification. Due to the formation of vortices, turbulent flow significantly affects the formation of macro-segregation than laminar flow, for example, in continuous steel casting, where magnetic stirring is an industrial practice. Several software programs have recently been developed to simulate solidification processes, where melt flow induced by magnetic stirring is also considered. However, in practical cases, it is almost impossible to prove by experiments what the type of melt flow was; at most, it can be deduced somewhat from the microstructure.

The effect of melt-flow on the microstructure has been investigated by performing several unidirectional solidification experiments where the melt has been flown in a rotating magnetic field. It is well-known that the angular frequency of the melt cylinder always differs from the angular frequency of the magnetic field. However, it proved to be very difficult to determine during the experiments. In our present study, the magnetic Taylor number and the Reynolds number were determined as a function of the radius of the melt cylinder, the magnetic induction, and the angular frequency of the magnetic field using the real angular frequency defined by the so-called pressure -compensation method developed earlier in the case of Ga75In25 alloy. The simulations developed for performing similar experiments can be checked, and the different experiments can be compared correctly using the obtained measurement results. By knowing the critical Reynolds number belonging to the laminar/turbulent flow transition, the value of critical magnetic induction belonging to the transition has been determined as a function of the radius of the melt cylinder. With the described experimental method, it has been possible to determine at what magnetic induction the flow would be turbulent. The results can be used to validate the software, and then validated software has a good chance of characterizing the flow of practical technologies.