Numerical study of large amplitude,nonsinusoidal motion and camber effects on pitching airfoil propulsion |
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| Institution: | 1. Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 08826, Republic of Korea;2. Department of Mechanical Engineering, Sunmoon University, Asan 31460, Republic of Korea;3. Department of Mechanical Engineering, KAIST, Daejeon 34141, Republic of Korea;4. Big Data Institute, Seoul National University, Seoul 08826, Republic of Korea;1. Department of Aerodynamics, Nanjing University of Aeronautics and Astronautics Yudao Street 29, Nanjing, Jiangsu 210016, China;2. School of Engineering and Information Technology, University of New South Wales Canberra, ACT 2600, Australia;3. Aerodynamics Development Department, AVIC Aerodynamics Research Institute Yangshan Street 1, Shenyang, Liaoning 110034, China;1. Department of Naval Architecture & Marine Engineering, University of Strathclyde, Glasgow G4 0LZ, UK;2. Department of Structural Engineering, University of California, San Diego, La Jolla, CA 92093, USA |
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| Abstract: | The effects of large amplitude and nonsinusoidal motion on pitching airfoil aerodynamics for thrust generation were numerically studied with a 2-D NACA0012 airfoil used, and various 2-D NACA asymmetric airfoils were applied for camber effect study. The large amplitude effect study has been undertaken over a wide range of reduced frequency k (from 6 to 18) and pitching amplitude θ (from 5° to 30°) at Re=1.35×104 with sinusoidal pitching profile used. It is shown that the large pitching amplitude results in much more thrust generated than that at low pitching amplitude and the increase of thrust with amplitude becomes slow when the amplitude reaches some degree. However, the propulsive efficiency noticeably decreases with the increase of θ at a fixed k.An adjustable parameter K was employed to realize various nonsinusoidal motions and the effect of nonsinusoidal motion was investigated with various unsteady parameters (θ, k) applied. The results reveal that nonsinusoidal motion has a noticeable effect on the aerodynamic performance, as it affects the instantaneous force coefficients, maximum thrust coefficients and flow structures. An increase in K results in a better thrust generation performance at fixed θ and k, especially for K>0. It is also shown that the larger K noticeably influences the wake pattern and induces a stronger reverse von Karman vortex street in the wake, which in turn leads to the increased thrust. The camber study was performed on various 2-D NACA airfoils with different cambers and camber locations undergoing sinusoidal pitching motion at θ=5° and Re=1.35×104. It is found that varying camber offers little improvement in thrust generation performance. |
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