Evolution of jets effusing from inclined holes into crossflow

The turbulent flow structure and vortex dynamics of a jet-in-a-crossflow (JICF) problem, which is related to gas turbine blade film cooling, is investigated using the particle-image velocimetry (PIV) technique. A cooling jet emanating from a pipe interacts with a turbulent flat plate boundary layer at a Reynolds number Re_∞ = 400,000. The streamwise inclination of the coolant jet is 30° and two velocity ratios (VR = 0.28, VR = 0.48) and two mass flux ratios (MR = 0.28, MR = 0.48) are considered. Jets of air and CO₂ are injected separately into a boundary layer to examine the effects of the density ratio between coolant and mainstream on the mixing behavior and consequently, the cooling efficiency. The results show a higher mass flux ratio to enlarge the size of the recirculation region leading to a more pronounced entrainment of hot outer fluid into the wake of the jet. Furthermore, the lateral spreading of the coolant is strongly increased at a higher density ratio. The results of the experimental measurements are used to validate numerical findings. This comparison shows an excellent agreement for mean velocity and higher moment velocity distributions.