Experimental and numerical analysis of free surface deformation in an electrically driven flow

The present paper presents the experimental and numerical results of an electrically induced flow in a cylindrical container (188 mm diameter) filled with a In–Ga–Sn alloy. The electric current is applied from copper electrodes of various diameters (4–8 mm) and varied from 100 to 700 A. The deformation of the free surface just under the electrode is reported in term of depth. At some critical current an arc develops around the electrode tip. To explore numerically what happens in such flows, calculations of the Magnetohydrodynamic (MHD) flow are performed. The numerical model is based on a potential formulation for the electromagnetic field. The evolution of the free surface flow is tracked with a VOF model. The electromagnetic parameters are fully coupled with the evolution of the free surface and the contact surface at the electrode. At low current density the interface is shifted downward by the pinch action of the Lorentz force. In the same time the rotational part of the Lorentz force drives the liquid metal flow in radial direction towards the electrode. The flow is accelerated towards the electrode and sinks in the form of a strong jet. At the high current density, the velocities are strong enough to induce further displacement of the interface by a Bernoulli mechanism. The combined action of the pinch and the rotational components of the Lorentz force on the interface displacement, scales as I2. The numerical and experimental results are in good agreements.

Surface of the liquid metal for the case of 5 mm electrode diameter. A plastic gain of pink colour surrounds the tip of the electrode. The applied DC current is 50, 100, 150, 250, 300 and 350 A. Circular waves are visible for I > 250 A. A dark area near the electrode appear when the cavern becomes deep and wide enough. For I = 350 A an arc appears around the electrode tip.Figure optionsDownload as PowerPoint slide