Recently, a great deal of attention has been focused on development of microfabricated devices for manipulating minute amounts of liquids. In particular, an extensive experimental work is devoted to generation, motion and manipulation of drops in microfluidic channels, or digital microfluidics. In the present work the numerical approach based on volume-of-fluid method, combined with the piece-wise linear interface reconstruction scheme, is implemented for modeling of droplet motion and forced heat transport in a droplet-laden laminar flow in a circular microchannel. The simulations show a very good agreement with asymptotic results concerning the motion of spherical and slender drops in confined laminar flows. The effective rates of the forced heat transfer in a droplet-laden flow are found to be superior over that in single-phase Poiseuille flow. The enhancement is anticipated to be a result of the flow disturbance in the carrier fluid due to propagation of a train of translating drops and efficient convective transport within drops due to internal circulation.

The steady two-dimensional viscous supersonic turbulent ow over a backward facing step was calculated using the PHOENICS CFD code. The two-equation k-turbulence model was employed for the turbulent ow simulation. The e ects of the incoming boundary layer, Reynolds number and inlet Mach number on the ow were investigated. The maximum free stream Mach number was 3.5. The PHOENICS code was found to be adequate for supersonic ow simulations with M 63:5, however, at hypersonic turbulent ow conditions convergence was not obtained. The numerical results indicate that the separation point is positioned on the step face, below the corner. The calculations also show that a lip shock is formed to match the ow conditions at the step corner. The results exhibit favorable agreement with data from both experiments and other numerical simulations.