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

— The study investigates the flow development in the vicinity and wake of a micro pillar mounted on a surface immersed in the inner region of a laminar boundary layer. The investigation is based on the numerical solution of the Navier Stokes equations for incompressible conditions. It is demonstrated that the significant wall-normal gradient of streamwise velocity of the cross flow spanning the height of the micro pillar results in suppression of time-periodic shedding of vorticity from the side surfaces of the micro pillar, resulting in a steady wake flow. A pair of streamwise-oriented tip vortices and a corresponding pair of base vortices are observed to dominate the wake development. The sources of vorticity for these vortices and their relation to the vorticity in the recirculation zone immediately downstream of the micro pillar are identified. This improved understanding of flow physics is intended to inform future studies of passive control of boundary layers.