Oscillatory flow and mass transfer within asymmetric and symmetric channels with sinusoidal wavy walls

Abstract

Mass transfer for oscillatory flow was studied experimentally in channels with two different geometries, i.e., a periodically converging-diverging channel and a serpentine channel, both having sinusoidal wavy walls. The experiments were carried out under the following conditions: 10<Re<500 and 0.008<St<0.05. The channel geometries were found to have an important effect on the flow patterns and the mass transfer rates. At low Strouhal numbers of less than 0.023, the mass transfer rates for both channels were almost identical, regardless of different flow patterns and wall shear stresses. At high Strouhal numbers, however, the serpentine channel had a smaller mass transfer rate than the converging-diverging channel. The mass transfer characteristics were explained in terms of the vortex dynamics, wall shear stresses and fluid mixing based on numerical analysis and flow visualizations. The serpentine channel yields a better mass transfer and pumping power performance than the converging and diverging channel at low Strouhal numbers.