T. Nishimura et S. Matsune, VORTICES AND WALL SHEAR STRESSES IN ASYMMETRIC AND SYMMETRICAL CHANNELS WITH SINUSOIDAL WAVY WALLS FOR PULSATILE FLOW AT LOW REYNOLDS-NUMBERS, International journal of heat and fluid flow, 19(6), 1998, pp. 583-593
Numerical simulation and flow visualization were performed to study th
e dynamical behavior of vortices generated in channels with two differ
ent geometries, i.e., a periodically converging-diverging channel and
serpentine channel, both having sinusoidal wavy walls. This system for
pulsatile flow is used to enhance heat and mass transfer in very visc
ous liquids. The numerical results predict well the dynamical behavior
of vortices and agree with the flow visualizations. For both channels
, the vortex expands in each furrow of the channel walls during the de
celeration phase and shrinks during the acceleration phase, which lead
s to fluid exchange between the vortex and the mainstream. The time-av
eraged vortex strength and wall shear stresses increase, as the freque
ncy of fluid oscillation increases under a fixed oscillatory fraction
of the flow rate. However, above a certain value of the frequency, the
y reversely decrease due to viscous effects. This frequency for the se
rpentine channel is smaller than that for the converging-diverging cha
nnel. The channel geometries are found to have an important effect of
the flow characteristics. (C) 1998 Elsevier Science Inc. All rights re
served.