Effect of sheared-induced diffusion on the transfer of heat across a sheared suspension

Suspensions of non-Brownian particles undergoing shear provide a quasi-unique system where mixing occurs spontaneously at low Reynolds number. In essence, particles behave in the fluid as so many ``stirrers.'' The questions raised are how do they affect the transport of heat/mass across sheared suspensions? What will be the influence of the particle size, their volume fraction and the applied shear? By using an index matched suspension and a laser induced fluorescence imaging technique, we were able to measure individual particle trajectories and correlate the particle diffusion motion to the thermal diffusion of the suspension. Particles cause a significant enhancement ($>$ 300\%) of the suspension transport properties. Simulations which combine a Lattice Boltzman technique to solve the flow and a passive Brownian tracer algorithm to solve for the transfer of heat are in very good agreement with experiments.