Experimental and numerical investigation of film cooling jet on a flat plate wind tunnel

An experimental and numerical study was conducted to investigate the unsteady behavior of film cooling jet for two different hole geometries on a flat plate wind tunnel. The numerical part was devoted to the assessment of different turbulence models to get the best prediction of both aerodynamic and thermal performance with a conventional RANS approach. The investigated hole geometries include a row of three cylindrical holes and a row of three fan-shaped holes with an inclination of 30 degrees with respect to the flat plate. Tests have been carried out at low speed and low inlet turbulence intensity level, with blowing ratios varied in the range of 0.5–1.5, and 1-2 for cylindrical and fan-shaped holes, respectively. Aerodynamic investigations have been performed by means of Laser Doppler Velocimetry (LDV), Particle Image Velocimetry (PIV), and Hotwire Anemometry (HW). LDV was used to study the boundary layer behavior just downstream of the holes. A high- resolution PIV system was used for flow visualization and flow field measurement to investigate the unsteady mixing process taking place between the coolant and main flow. Furthermore, HW has been used to measure velocity components in a vertical-lateral plane. For thermal measurements, the binary PSP technique was used to measure adiabatic film cooling effectiveness. Results obtained from aerothermal experiments show that by expanding the exit of the cooling hole, the penetration of the cooling jet is significantly reduced relative to the cylindrical hole, thereby providing a better coverage over the flat plate even at high blowing ratios. Furthermore, the effect of density ratio was investigated using CO2 as a foreign gas. In the same BR, the jet with a greater density ratio provides better film protection over the flat plate surface. Finally, detailed experimental data was compared with three turbulence models, which are RKE, SST KW, and RSM turbulence models, in the state-of-art CFD code STAR-CCM+, result in selecting SST KW and RSM turbulence models for cylindrical and fan-shaped holes, respectively.