Jeudi 11 septembre 2025 à 11h00, salle des séminaires IRPHE
Acoustic streaming refers to the steady, time-averaged fluid motion induced by the propagation of acoustic waves in viscous media. It typically arises from the dissipation of acoustic energy, either within viscous boundary layers (boundary-driven streaming) or in the fluid bulk (bulk-driven streaming). Although the phenomenon has been studied since the seminal works of Faraday, Stokes, and Rayleigh in the 19th century, research on acoustic streaming remains highly active due to its importance in applications such as medical ultrasound and microscale acoustofluidics. In this seminar, we will focus on boundary-driven acoustic streaming. We begin by presenting our recent discovery of streaming suppression that occurs when two types of solute molecules are laminated within a microchannel. This effect results from the competition between the acoustic body force, arising from gradients in fluid density and compressibility, and the shear stress responsible for inducing boundary-driven streaming. We will then discuss acoustic streaming in the presence of a temperature gradient, which may originate either from optical heating or from heating within viscous boundary layers under conditions of high acoustic energy density. Finally, we will introduce recent investigations of acoustic streaming in viscoelastic fluids, highlighting the discrepancies observed between theoretical predictions and experimental measurements.
Short bio: Wei Qiu received his Ph.D. degree from Tokyo Institute of Technology in 2015. He then worked as a postdoctoral fellow at Tokyo Institute of Technology, Technical University of Denmark, and Lund University, under various schemes including JSPS Research Fellowships for Young Scientists, H.C. Ørsted COFUND Postdoc Fellowship, Wenner-Gren Foreign Postdoctoral Fellowship, and Marie Curie Fellowship. In 2022, he became a tenure-track assistant professor in the Department of Biomedical Engineering, Lund University. His research focuses on physical acoustics, with a particularly emphasis on microscale acoustofluidics. He is currently holding 10 MSEK research funding, including the Starting Grant from Swedish Research Council.