Acoustic streaming enhanced mass transfer at a wall
By Ghani, Nouhayla El; Miralles, Sophie; Botton, Valéry; Henry, Daniel; Hadid, Hamda Ben; Ter-Ovanessian, Benoît; Marcelin, Sabrina
Published in International Journal of Heat and Mass Transfer
2021
Abstract
The influence of an impinging acoustic streaming jet on wall mass transfer is studied both experimentally and numerically. The idea is to show that acoustically-driven jets generated by ultrasounds can be used to enhance transfer phenomena at a distance, by creating localized friction zones. An experimental setup has been developed consisting in a cavity containing an electrolytic solution of [Fe(CN)6]4−/[Fe(CN)6]3−. A jet forced by an ultrasound beam impinges on the upper wall instrumented with electrodes, at which the mass transfer influenced by the streaming is measured by electrochemical technics. Numerical simulations of the flow and mass transfer in the same configuration are also performed. A significant enhancement of the mass transfer at the electrodes (represented by the Sherwood number Sh) with the injected acoustic power (quantified by the acoustic Grashof number Grac) is observed. An order of magnitude of the expected Sherwood number and friction coefficient is proposed on the basis of the Leveque law and momentum budget considerations. Scaling laws involving both experimental and numerical mass transfer at the electrodes (Sh), numerical wall shear stress and injected power (Grac) are finally derived.