FLUID MIXING AND MASS-TRANSFER IN 2-DIMENSIONAL CAVITIES WITH TIME-PERIODIC LID VELOCITY

Fluid mixing and mass transfer in cavities with time-periodic lid velo city were examined numerically. Unsteady Galerkin finite elements comp utations were performed for various flow parameters. Global fluid mixi ng is greatly promoted when an unsteady component of the velocity is s uperimposed on the steady flow. There is an optimum oscillation freque ncy that produces the best mixing. Fluid mixing also depends on the os cillation amplitude and the geometric aspect ratio. However, the oscil lation frequency has little effect on mass transfer between the walls at different concentrations. It is revealed that excellent global flui d mixing does not always lead to heat and mass transfer enhancement. ( C) 1997 by Elsevier Science Inc.