Boundary Layer Flow Induced by Pitched and Skewed Jets in a Freestream

Pitched and skewed jets issuing through small holes in a wall into a freestream have proven effective regarding the control of boundary layer separation. Longitudinal vortices are produced by the interaction between the jets and the freestream. In this method, the fluid particles which have large energy of the freestream are supplied to decelerated fluid particles in the boundary layer by longitudinal vortices. In order to have a better understanding of the suppressing mechanism of longitudinal vortices, the velocity measurements were carried out in a region close to the wall for the various jet pitch angles. In the case of a large pitch angle (measured from lower wall), longitudinal vortices exist apart from the lower wall under influence of the velocity induced by the vortex pair. The flow in the boundary layer is affected by a pitch angle. Longitudinal vortices produced by the small jet pitch angle strongly disturb the flow in the boundary layer and therefore effective separation control is attained.