Surface streak experiments coupled with flow visualization and numerical simulations were used to investigate short length-to-diameter injection holes for geometries of interest to the gas turbine industry. The flow field results were also related to measured surface heat transfer in the downstream region of the jets. Geometric surface topology maps inferred from "oil and lampblack" surface streak experiments give insights into the flow field, as well as boundary layer disruption, and ultimately the convective heat transfer coefficient enhancement in the wake region of the jets.
A secondary counter-rotating vortex pair (CRVP) with the opposite sense of rotation as the well documented main counter-rotating vortex pair is found to enhance the attachment event in the wake region and correspondingly increase the center line enhancement of the convective heat transfer coefficient. In addition to providing information about the crossflow boundary layer disruption, the surface topological results relate the signature of the surface shear stress to the coherent flow structures in the flow field being investigated.