Experimental Investigation of Transonic Shock Oscillations on NACA 0018 at Incidence
A NACA 0018 airfoil model with a 3-inch chord was mounted into the trisonic wind tunnel at the National Center for Physical Acoustics at the University of Mississippi. Tunnel runs were conducted with the angle of incidence increasing from 0 degrees to 6 degrees at 1 degree increments, while the Mach number was held steady at 0.73. High-speed schlieren images were recorded at a sample rate of 4,000 Hz. A Matlab code was developed to display the spatial power spectral density distribution in the region of the shock. This code calculated the frequency spectrum at regular points along the range of shock motion and plotted the spatial distribution of frequency spectra across all the points. This identified the location of the high-amplitude frequencies, which indicated the precise range of the shock motion as well as its dominant oscillation frequency. It was found that, for each degree increase, the frequency of oscillations increased by approximately 10.8 Hz. This is equivalent to a reduced frequency increase of 0.0205 per degree.
Angle Of Incidence, Boundary Layer Separations, Buffeting, Symmetrical Airfoils, Transonic Shock Oscillations, Aerospace Engineering
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