Effect of crucible wall roughness on the laminar/turbulent flow transition of the Ga75ln25 alloy stirred by a rotating magnetic field

The critical magnetic induction (Bcr) values of a melt flow produced by a rotating magnetic field (RMF), remaining laminar or turbulent, are essential in different solidification processes. In an earlier paper (Metall Res Technol 100: 1043-1061, 2003), we showed that Bcr depends on the crucible radius (R) and frequency of the magnetic field (f). The effect of wall roughness (WR) on Bcr was investigated in this study. Using ten different wall materials, we determined the angular frequency (w) and Reynolds number (Re) as a function of the magnetic induction (B) and f using two different measuring methods (pressure compensation method, PCM; height measuring method, HMM). The experiments were performed at room temperature; therefore, the Ga75wt%In25wt% alloy was chosen for the experiments. Based on the measured and calculated results, a simple relationship was determined between Bcr and Re*, f, R, and WR, where the constants K-1, K-2, K-3, and K-4 depended on the physical properties of the melt and wall material: Bcr(Re*,f, R, WR) = Re*/R-2 (K(1)f(-K2) + K(3)f(-)(K4)WR)