Drag characteristics of unsteady, perturbed boundary layer flows
Abstract
A series of timedependent numerical computations have been performed for the flow of an unsteady boundary layer over an embedded cavity, which is aligned normal to the flow direction. The unsteady flow is the result of the imposition of a Stuart vortex, at the inflow boundary of the computational domain, onto an otherwise unperturbed twodimensional laminar boundary layer flow. This produces a strongly vortical, but spatially monochromatic, motion at inflow which is allowed to evolve downstream through the timedependent numerical solution of appropriate conservation equations. As the imposed vortex evolves over the solid boundary, a weaker induced vortical motion is produced and together these perturbing motions interact with the fluid motion in the embedded cavity. An analysis of the pertinent dynamic variables as well as the timedependent drag characteristics for this type of nonplanar geometry is performed; with particular emphasis on the relative contribution of both pressure drag and frictional drag at various times in the evolution process.
 Publication:

American Institute of Aeronautics and Astronautics
 Pub Date:
 March 1985
 Bibcode:
 1985shfc.conf.....G
 Keywords:

 Boundary Layer Flow;
 Computational Fluid Dynamics;
 Drag Reduction;
 Time Dependence;
 Unsteady Flow;
 Vortices;
 Cavities;
 Conservation Equations;
 Differential Equations;
 Reynolds Number;
 Surface Roughness;
 Fluid Mechanics and Heat Transfer