Optimal Control of Boundary Layers under Body Forces

Abstract

Streamwise vortices developing in flows due to the interaction of viscous and body forces are important to study both for the basic insight into the laminar-turbulent transition phenomenon, and for practical applications dealing with transport processes in boundary layers. Matched numerical and experimental studies based on the Goertler stability theory and receptivity to induced longitudinal vortices enabled to observe the vortical structure evolution across the boundary layer thickness and downstream (or in time) and to formulate a logically stipulated approach to the vortex dynamics management. The basic idea proposed for optimal flow control is the utilization of an inherent dominating structure (streamwise vortices) of the flow under body forces. Being generated strictly according to the basic flow parameters, the streamwise vortices were shown either to stabilize the flow situation (extending a stage of the laminar-turbulent transition) or to intensify mixing processes near the wall (e.g. delaying flow separation or enhancing heat transfer).