On the dominant vortex created by a pitched and skewed jet in crossflow

Vortex Generating Jets (VGJs) are jets that pass through a wall and into a crossflow to create a dominant streamwise vortex. The jets are produced by flow through holes in the wall that are pitched with respect to the wall and skewed with respect to the crossflow. For low jet to crossflow velocity ratios, the dominant vortex remains embedded in the crossflow boundary layer along the wall. The embedded vortex has important consequences for boundary layer separation control and film cooling applications.; Flow visualization experiments were used to investigate the vorticity dynamics of the interaction between the jet and the crossflow. It was found that the core of the dominant vortex consisted primarily of jet boundary layer fluid. Vorticity generation mechanisms, at the wall near the jet-orifice, combined with the realignment and stretching of vorticity that originates from the boundary layer in the jet-hole form the dominant vortex core. The dominant vortex is closely related to the counter-rotating vortex pair created by a normal jet in crossflow (one with no pitch or skew).; Detailed planes of three-component Laser Doppler Velocimetry (LDV) measurements were obtained at several downstream locations and for several different VGJ configurations to study how the embedded dominant vortex modified the turbulent boundary layer. For a given jet to crossflow velocity ratio, the VGJ configuration of 60° skew and 30° pitch produced the strongest dominant vortex. Higher velocity ratio jets produced stronger dominant vortices which were located further from the wall. Increasing the pitch angle also placed the vortex further away from the wall. Measurements over the jet-orifice demonstrated that there is significant secondary flow in the jet-hole upstream of the jet-orifice.; In studying the downstream development of the embedded vortex, several features were noted. Peak magnitudes of most turbulent stresses decreased exponentially. At most locations the turbulent transport vectors of the turbulent kinetic energy, q2/2, followed the gradients of q2/2, implying that diffusion transport modeling is appropriate for this quantity. The same could not be said of the six individual Reynolds shear stresses. Mean convection dominated the downstream evolution of streamwise vorticity. m evolution of streamwise vorticity.