Effect of crucible wall roughness on the laminar/turbulent flow transition of the Ga75In25 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 (ω) 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: B c r Re ∗ , f , R , W R = Re ∗ R 2 ( K 1 f - K 2 + K 3 f - K 4 W R )