Velocity measurement on a heated vertical wall under a transverse magnetic field using ultrasonic doppler velocimetry

The velocity boundary layer profile for an electrically conducting liquid over a heated vertical flat plate is measured using Ultrasonic Doppler Velocimetry (UDV) technique under a transverse magnetic field. A strong neodymium permanent magnet (of strength 0.35 Tesla on the surface) is kept on the rear side of the heated wall to produce a transverse magnetic field. The liquid used is the 5% and 10% (by weight) aqueous solutions of table salt. The velocity profile is measured at a fixed position of the plate for varying temperature differences \((\Delta T)\) $(\mathrm{\Delta }T)$ ( \(5, \;10, \;15\; ^\circ {\text{C}}\) $5,10,15{}^{\circ }\text{C}$ ) and at different Hartmann numbers ( \(Ha\) $\mathit{Ha}$ ) (0, 0.086, 0.75, and 0.93) under quasi-static heating condition. In this experimental study, we also demonstrate how to measure the velocity on a plane transverse to the wall by moving the UDV probe. Due to relatively low Hartmann numbers, the effect of Lorentz force in comparison with buoyancy is small; nevertheless, a cumulative volumetric force stretches the velocity boundary layer thickness under the applied external magnetic field. Our technique may be used with other conducting liquids such as liquid metals where the Ha is expected to be much larger.