Unsteady surface pressure measurement on a pitching air foil

Abstract

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.

An experimental analysis of the unsteady pressure distribution on a two dimensional pitching Eppler- 361 airfoil was conducted by using transducers at low speed wind tunnel. Dynamic pitching motion was produced by oscillating the model over a range of reduced frequencies, k=0.02355- 0.1413. In addition, Static data were recorded as base line for analysis and comparison. Both static and oscillatory tests were conducted at Reynolds numbers of 5 Re 5. The angle of attack of the model was varying between 0 to 15 degrees. Surface static pressure was measured for both upper and lower surfaces. Pitch rate, Reynolds number and oscillation amplitudes and mean angle of attack were varied to determine the effect on pressure distributions. During the test a series of the quasi-sinusoidal pitching motion were imposed to the model. At different reduced frequency the hysteresis loops were observed in variation of Cp vs.α. Hysteresis loops when plotted against the angle of attack were both clockwise and counterclockwise. It was found that pitching amplitudes, reduced frequency had strong effects in pressure distribution, near the leading edge of the airfoil.