Study of Shock Wave Boundary Layer Interaction Using Pressure-Sensitive Paint

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The Ohio State University

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Through the advancement of aviation, engineers and designers have strove to improve the performance of aircraft and push through the various flight regimes. As aircraft encounter transonic flight, compressibility effects begin to impose limitations and impede their performance. One such limitation comes from the shock wave boundary layer interaction, also known as buffeting, that occurs on the wings of aircraft but more so on the blades of rotor-craft. Prior work in this study has investigated the effects on oscillating free stream Mach numbers on a NACA0012 airfoil due to its relevance to helicopter aerodynamics. These studies were conducted with the airfoil at a fixed angle of attack with the Mach number set to oscillate in and out of the known buffet conditions. By oscillating the flow with a rotating cam, the Mach number can be forced to mimic the periodically varying freestream velocity conditions that a rotor blade would experience in forward flight. In these experiments the presence of oscillatory shock waves at high subsonic speeds and their physical mechanisms are not fully understood. This experiment sets out to use Pressure Sensitive Paint (PSP) as a method of detecting buffet on the surface of an airfoil by obtaining global surface pressure distribution in transonic flight conditions. The tests include steady runs as a baseline as well as oscillatory free stream velocity fields on a NACA 0012. The pressure taps were used to validate the PSP results. A fast-acting single-luminophore pressure sensitive paint applied to a polymer-ceramic basecoat was chosen for the experiments. The PSP measurements were made using an intensity-based pressure-sensitive paint technique that utilized a high-speed camera and Ultra-Violet LED arrays. This technique allows for accurate unsteady pressure measurements in the oscillating flow field.



Shock wave, boundary layer, pressure-sensitive paint, buffet