Experimental Investigation of the Flow Structure around a Pitching Airfoil by Mean and Instantaneous Data

Document Type : Research Paper

Authors

1 Ph.D. Candidate, Department of Mechanical Engineering, Hakim Sabzevari University, Sabzevar, Iran

2 Corresponding Author, Professor, Department of Mechanical Engineering, Hakim Sabzevari University, Sabzevar, Iran

Abstract

This paper focuses on a selected set of results from extensive experimental tests to characterize the wake aerodynamics of an SD7062 wind turbine airfoil in steady-state and pitch oscillating motion. Investigating the wake of an airfoil provides outstanding information on physical aspects of the downstream. Wake measurements were accomplished through hot-wire anemometers in the Laboratory of Aerodynamics at the Hakim Sabzevari University. The impact of AoA and Reynolds number were both examined in the steady-state. Regarding the pitching airfoil motion, the effect of reduced frequency, Reynolds number, symmetric, and asymmetric oscillation were also investigated. The results revealed that in both the pitching and the steady-state cases, strength of the vortices is highly related to the airfoil shape, amplitude, and Reynolds number. In respect of pitching state, the TI value is decreased as the Reynolds number increases, while it grows up with increasing the reduced frequency. Besides, TI in asymmetry oscillation is significantly higher than in symmetric oscillation, which is probably due to the formation of larger vortices. For steady-state, the instantaneous TI and velocity are almost the same as their mean values. Hence, statistical data could be used to calculate aerodynamic forces on a static airfoil. It is necessary to meticulously consider the effect of mean and instantaneous forces in the pitching state, as the forces acting on the pitching airfoil could reach several times its average state in some moments during its impact. As a result, the importance of these instantaneous loads is required to be considered enabling us to select the proper material for the airfoil.

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References

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