In the present study the dynamic lift and drag acting on the pitching airfoils such as a flat plate, NACA0010, NACA0020, NACA65-0910 and BTE have been measured by using a sixaxes sensor in a water tunnel at low Reynolds number region under the condition of various pitching frequencies. The unsteady characteristics of the dynamic lift and drag have been compared with the quasi-steady ones which are measured in the steady state condition. The pitching motion is available for keeping the lift higher even after the separation occurs. The characteristics of the dynamic lift is quite different from the quasi-steady one at high pitching frequency region such as 3.0 Hz in the amplitude as well as in the phase. As the pitching frequency decreases, the amplitude of the dynamic lift becomes closer to the quasi-steady one. However, the phase remains different between the steady and unsteady conditions even at low pitching frequency such as 0.05 Hz. On the other hand the dynamic drag is governed strongly by the angle of attack.
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