Date of Award

4-1994

Degree Name

Master of Science in Engineering

Department

Mechanical and Aeronautical Engineering

First Advisor

Dr. Parviz Merati

Second Advisor

Dr. Richard B. Hathaway

Third Advisor

Dr. Judah Ari-Gur

Access Setting

Masters Thesis-Open Access

Abstract

This research investigated the effects of internal acoustic excitation on the boundary layer and surface of an airfoil. A NACA 16- 018 symmetric airfoil was tested in the Western Michigan University wind tunnel. The shedding vortex frequency of the airfoil was determined using hot-film anemometry. Using stroboscopic and holographic interferometry, the natural frequencies of the airfoil surface were determined. The airfoil surface was tuned such that the frequency of the shedding vortex is a resonant frequency and two internally mounted acoustic drivers were used to excite the surface of the airfoil at the shedding vortex frequency. The effects on pressure drag of acoustic excitation at various amplitudes were recorded. A reduction in drag of approximately 5-7% was recorded with excitation at 100 Hz and 83 dB and the power per unit area saved from a reduction in drag was approximately 1600 to 2800 times greater than that required to excite the boundary layer flow. A reduction in pressure drag has the potential of improving the efficiency of current airfoils and leading to better airfoil designs.

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