Influence of Fluid Viscoelasticity on Acoustic Streaming in Microchannels

The emergence of acoustofluidic systems has enabled innovative techniques for microscale manipulation of biologically relevant fluids to enable promising applications such as sputum liquefaction, whole blood pumping, and cell sorting. However, while most biological fluids (e.g., blood, saliva, cytoplasm) are inherently viscoelastic, our understanding of acoustofluidic phenomena in such fluids is largely shaped by Newtonian fluid models. As a result, the understanding of nonlinear, time-averaged effects—such as acoustic streaming and radiation forces—in viscoelastic media remains limited.



In this work, we present a numerical investigation of acoustic streaming in an acoustically-actuated viscoelastic fluid. The fluid is modeled using the Oldroyd-B constitutive model. Following standard acoustofluidic modeling approach, a perturbation expansion is employed to decompose the fluid response into oscillatory acoustic and time-averaged components. Our results demonstrate that, depending on the relaxation time and polymer viscosity, the resulting streaming field can deviate significantly both qualitatively and quantitatively from that in a Newtonian fluid. These results illustrate the possibility of realizing enhanced fluid mixing and transport beyond what is achievable in Newtonian fluid systems.