Characteristics of sliding bubble in aqueous electrolyte: In presence of an external magnetic field

An experment was carried out to examine the influence of an external magnetic field on a bubble in an aqueous electrolytic cell. In the electrolysis process, bubbles nucleate instateneously and the electrolytic flow is mostly caused by swarm of bubbles, which makes it difficult to quantify the impacts of various forces, in particular the magneto-hydrodynamic (MHD) and gravity forces in Hall-Héroult cells. In this paper, an aqueous-electrolytic cell was designed to allow a single bubble to slide underneath the inclinde anode in an electrolytic environment and in presence of an external magnetic field. Air was injected at a constant flow rate of 6.2 ml/min through a 3 mm diameter orifice into a quiescent conducting aqueous electyrolytic media. Experiments were conducted both with and without external-magnetic field for varying anode-inclinations ranging from θ = 4°, 6° and 8° in order to quantify the order of magnitude of MHD force in comparison to the gravity force. The data clearly shows that, in presence of the magnetic field, the bubble changes its shape and orientation at the onset of nucleation, which in turn gives rise to a non-linear trajectory across the longitudinal axis of electrode establishing a large circulatory flow within the electrolytic cell. In general, the experimental data shows that the bulk velocity was found to be dominated by the MHD driven flow overshadowing the influence of gravity force.