An Experimental Study of Compressibility Effects on the Film Cooling Effectiveness Using PSP and PIV Techniques Wenwu Zhou 1 , Blake Johnson 2 , Hui Hu 3 () Department of Aerospace Engineering, Iowa State University, Ames, Iowa, 50010 An experimental study was performed to examine effects of compressibility on film cooling effectiveness for coolant flowing from cylindrical holes in a flat plate. The incoming flow Mach number was set at 0.07, 0.30, 0.50 and 0.70. The Pressure Sensitive Paint (PSP) technique, which is based on a mass transfer analogy, was used to map the adiabatic film cooling effectiveness distribution on the surface of interest. The high- resolution PSP measurement result showed that there was marginal enhancement of film cooling performance for higher Mach number flow comparing to the Ma=0.07 case. A high-resolution Particle Image Velocimetry (PIV) system was also used to conduct detailed flow field measurements to uncover the underlying physics of film cooling in the high speed flow, which showed similar flow field measurement results at M=0.4 for both Ma=0.07 and 0.30 cases, but slightly different ensemble-averaged velocity distribution was found for M=1.25 case. Nomenclature M = Mass flux ratio of the coolant and mainstream flow, c c V V     I = Momentum flux ratio of the coolant and mainstream flow, 2 2 c c V V     DR = Density ratio of the coolant and mainstream, c    D = Diameter of hole aw  = Adiabatic film cooling effectiveness at the wall aw T = Adiabatic wall temperature at the wall c T = Temperature of the coolant T  = Temperature of the main stream flow  = Thermal diffusion coefficient s D = Concentration diffusion coefficient of species Le = Lewis number, s D    2 o main C = Oxygen concentration of mainstream   2 o mix C = Oxygen concentration of mainstream-coolant mixture at the wall   2 o coolant C = Oxygen concentration of cooling flow   2 o air p = Partial pressure of oxygen with air as the coolant   2 o mix p = Partial pressure of oxygen with N 2 or CO 2 as the coolant   2 o ref p = Partial pressure of oxygen at reference state b I = PSP image intensity of background noise ref I = PSP image intensity of the excitation light at the reference state without flow 1 Graduate Student, Department of Aerospace Engineering. 2 Postdoctoral Associate, Department of Aerospace Engineering, Present address: Visiting lecturer, Department of Mechanical Science & Engineering, University of Illinois, Champaign, IL 61801. 3 Professor, Department of Aerospace Engineering, AIAA Associate Fellow, Email: huhui@iastate.edu Downloaded by Hui Hu on January 18, 2015 | http://arc.aiaa.org | DOI: 10.2514/6.2015-0352 53rd AIAA Aerospace Sciences Meeting 5-9 January 2015, Kissimmee, Florida AIAA 2015-0352 Copyright © 2015 by Wenwu Zhou, Blake Johnson and Hui Hu. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. AIAA SciTech