Sommaire:

Mixing viscous fluids is difficult. The question addressed here is how the presence of rigid particles in a viscous shear flow accelerates this process. This information is crucial for instance to predict the transport of drugs or oxygen in blood flow or the transport of nutrients inside biological cells undergoing cytoplasmic-streaming. Here, high-resolution measurements of the fluid phase velocity field are performed in a model sheared suspension to reconstruct the stretching histories of material lines within the interstitial fluid. We found that the presence of particles changes the very nature of the flow kinematics: stretching in a pure shear flow is linear, it becomes exponential and widely distributed (converging to a log-normal) in the presence of particles. These trends can be well captured by multiplicative stretching process based on the distribution of local shear-rates and their persistence time. This complete description of the flow kinematics allows us to make predictions for the mixing times and show how, and in which limit, the presence of particles accelerates mixing within sheared suspensions.

Pour plus d'informations, merci de contacter Berthier L.