Abstract
Experimental investigations were carried out to study the wake profile of a supercritical airfoil at Mach numbers of 0.4 and 0.6 in a pitching motion. Both static and dynamic tests were conducted in a tri-sonic wind tunnel. Flow field inside the wake was measured by hot wire anemometry at downstream distances of 0.25 and 0.5 times the chord length from trailing edge. All data were taken at mean incidence angle of 3°; the amplitude of oscillation was 3° and the oscillation frequencies were 3 and 6 Hz. Moreover, numerical study was applied for the same airfoil under similar experimental test conditions; finally, wake profiles obtained from both numerical and experimental methods were compared.
Highlights
It is important to consider the unsteady aerodynamic behavior of airfoils to understand the problems associated with flutter and buffet
Hot wire anemometry has been used widely in subsonic flow and sometimes in supersonic flow. Major problems such as wire breakage due to high dynamic pressures, dust particles and vibrations limit the application of hot wires in transonic flows
Much research has been conducted into the study of unsteady flow wake, there is steel much to do to investigate the wake profiles by hot wire anemometry in compressible flows
Summary
It is important to consider the unsteady aerodynamic behavior of airfoils to understand the problems associated with flutter and buffet. Bodapatti and Lee (1984) studied wake profiles of an airfoil along with an oscillating flap in a transonic flow They used pressure sensors besides hot wires and compared the results. To measure the velocity in wake region, they used hot wire anemometry and applied smoke wire visualization method to illustrate the flow Their observations revealed that the shedding frequency in wake region of an oscillating airfoil was quite different from that of a fixed airfoil at a specified angle of attack; variation of shedding frequency was diminished as the reduced frequency of oscillation increased. Wake of a supercritical airfoil is measured in compressible flow by means of hot wire sensors in a transonic wind tunnel for both fixed and oscillating airfoil. Calibration of sensor voltage is carried out by in-direct method and velocity profiles are obtained inside the wake. Mach contours and velocity profiles are obtained from numerical analysis and compared with experimental results
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