Flexible flapping airfoil propulsion at low reynolds numbers


Heathcote, S. and Gursul, I., 2007. Flexible flapping airfoil propulsion at low reynolds numbers. AIAA Journal, 45 (5), pp. 1066-1079.

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Water tunnel experiments on chord wise-flexible airfoils heaving with constant amplitude have been carried out for Reynolds numbers of 9,000 to 27,000. A degree of flexibility was found to increase both thrust coefficient and propulsive efficiency. Measurements of the flow field revealed stronger trailing-edge vortices corresponding to higher thrust coefficients, and weaker leading-edge vortices corresponding to higher efficiencies. By analogy with a rigid airfoil in coupled heave and pitch, thrust coefficient and propulsive efficiency were found to be functions of the Strouhal number and pitch phase angle. Propulsive efficiency peaks at a pitch phase angle of 95-100 deg (consistent with experimental and computational simulations of rigid airfoils in coupled heave and pitch), and a Strouhal number of 0.29, which lies in the middle of the range observed in nature. Thrust peaks at pitch phase angles in the region of 110-120 deg, but at higher Strouhal numbers. The results suggest the effect of chordwise flexibility is beneficial for purely heaving airfoils at low Reynolds numbers.


Item Type Articles
CreatorsHeathcote, S.and Gursul, I.
Uncontrolled Keywordsaircraft propulsion,flow fields,airfoils,strouhal number,vortex flow,reynolds number
DepartmentsFaculty of Engineering & Design > Mechanical Engineering
Research CentresAerospace Engineering Research Centre
ID Code1621


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