Propulsion via buoyancy driven boundary layer

Abstract

Heating a sloped surface generates a well-studied boundary layer flow, but the resulting surface forces have never been studied in propulsion applications. We built a triangular wedge to test this effect by mounting a resistive heating pad to one of its conducting sloped surfaces. We submerge the wedge within a two-layer water stratification, turn the heater on and track the wedge's motion. We have observed a propulsion speed of 0.613 ± 0.042 mm/s with a temperature difference between the heated surface and ambient fluid of 4°C. We also use theory and numerics to predict the propulsion speed and predicted a speed of 1.43 mm/s, within an order of magnitude of the observed results, and thus our model was validated by the experiments.