Numerical Study of the Fluid Dynamics of a Micro Pillar Immersed in a Laminar Boundary Layer

Flow Over Micro Pillars Immersed In A Laminar Boundary Layer: Effects Of Micro-Pillar Geometry And Tandem Interaction

“…infinitely long) cylinder in uniform cross flow at these flow Reynolds number values falls in the 40-150 Reynolds-number range for which the cylinder would experience transient alternating vortex shedding from its starboard and port sides to produce the well-known Karman vortex street. The present simulation results and those in the precursor study [17] indicate a steady flow field for all the configurations considered. The aspect ratio of the micro pillar may affect this outcome.…”

“…4c. As was demonstrated in the precursor study [17], the source of vorticity for the base vortices is the boundary layer developing on the micro-pillar side surface. The vorticity of this boundary layer develops a streamwise (x) component due to the cross-flow velocity gradient along the height of the micro pillar.…”

“…Based on the flow physics reviewed in the foregoing, placing the free end of the cylinder within this high-vorticity region may yield dynamics that deviate from the trends observed for cylinders where the undisturbed-flow vorticity near the free end of the cylinder is either low or zero. A computational study recently conducted by the present authors for such a configuration [17] demonstrated a unique wake development for a surfacemounted micro pillar immersed in the inner region of the surface boundary layer. The present study builds on this initial work by investigating variations in the micro pillar dimensions and a configuration involving two micro pillars in tandem.…”

“…A saddle point forms in the same plane at the base of the micro pillar. In the precursor study [17], these points were shown to be the unique result of the micro pillar being immersed in a flow of significant gradient in streamwise velocity. For the shorter micro pillar (H/D=2.5), these points are noted at very similar relative positions along the height of the micro pillar, as illustrated in Fig.…”

“…It may therefore be argued that this gradient plays a significant role in suppression of periodic shedding from the micro pillar. Analysis of the flow field around the micro pillar and its wake as presented in the recent precursor study [17] with reference to Fig. 3 helped to further explore this causeand-effect relationship.…”