Experimental investigation of Boundary Layer on an Oscillating (Pitching) Supercritical Airfoil in Compressible Flow Using Multiple Hot Film Sensors

Authors

Abstract

Aerodynamic characteristics of an airfoil are highly affected by the behavior of the boundary layer. This behavior, and the related phenomena, depends on such different parameters as Reynolds number, angle of attack, unsteady motion, local Mach number,and compressibility. In this paper a series of static and dynamic (pitching motion) tests at pre stall angle of attacks were performed in a high speed wind tunnel to study the steady and unsteady behavior of the compressible boundary layer on a Supercritical Airfoil. Some static tests were performed at Mach numbers of 0.4, and 0.5 whit maximum angles of attack of 6⁰ and oscillation amplitudes of 1⁰ and 3⁰ and oscillation frequencies of 3 and 6Hz in Sinusoidal pitching motions. Measurements involved pressure distribution and shear stress variations using multiple hot film. The effects of compressibility, free stream Mach number, mean angle, reduced frequency and oscillation amplitude were investigated. Results show delay in transition in pitching motion with respect to steady conditions, and asymmetry between transition and relaminarization during pitching motion.

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