Near wall measurements in a separating turbulent boundary layer with and without passive flow control

Abstract

The present paper reports the results of a detailed experimental study on low profile vortex generators used to control a turbulent boundary layer separation on a large-scale flat plate with prescribed adverse pressure gradient, which conditions are representative of aggressive turbine intermediate ducts. Laser Doppler Velocimetry has been employed to investigate the velocity fields in different measurement planes to characterize the turbulent boundary layer at separation conditions, without and with control devices application. The detail of the performed measurements allows the evaluation of the deformation works in the test section symmetry plane; normal and shear contributions of viscous and turbulent deformation works have been distinctly analyzed. Furthermore the analysis on the flow generated by VGs has been extended evaluating velocity and turbulence profiles in a cross stream plane immediately downstream of the control device.