Mode regulation of elastic instability from non-Brownian suspension

Introduction: Viscoelastic fluid carrying suspension is ubiquitous in engineering applications. When the shear rate is high, the visco-elastic flow tends to be unstable. And secondary flows will emerge. This phenomenon is named elastic instability.  In this experimental work, we combined rheo-microscope, rheo-flow visualization, and dynamic mode decomposition. We investigated the influence of finite volume fraction non-Brownian suspension on the elastic instability of visco-elastic shear flow. We found that, in the visco-elastic flow, suspension assembles to large ordered structures, even under a volume fraction far lower than the random close pack. Further, such structures will regulate the secondary flow, which suppresses higher-order modes of the secondary flow. This research highlights the connections between suspension structures and the elastic instabilities of a viscoelastic flow and provides guidelines for the use of suspensions in viscoelastic fluid in industrial applications.