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AIRFOIL CHARACTERISTICS AT A LOW REYNOLDS NUMBER

S. Sunada
Mechanical Engineering Laboratory, AIST, MITI, 1-2 Namiki, Tsukuba-shi, Ibaraki-ken, 305-8564, Japan

K. Ozaki
Mechanical Engineering Laboratory, AIST, MITI, 1-2 Namiki, Tsukuba-shi, Ibaraki-ken, 305-8564, Japan

M. Tanaka
Mechanical Engineering Laboratory, AIST, MITI, 1-2 Namiki, Tsukuba-shi, Ibaraki-ken, 305-8564, Japan

T. Yasuda
Nihon University, 7-24-1 Narashinodai, Funabashi-shi, Chiba-ken, 274-8501, Japan

K. Yasuda
Nihon University, 7-24-1 Narashinodai, Funabashi-shi, Chiba-ken, 274-8501, Japan

Keiji Kawachi
University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo, 153-8405, Japan

ABSTRACT

Corrugation and leading-edge sharpness enhance the airfoils of insect wings and model airplanes, respectively. To clarify this enhancement, the effects of corrugation and leading-edge sharpness on airfoil characteristics at low Reynolds number (4 × 10³) were investigated by measuring the hydrodynamic force acting on such airfoils and by flow visualization.
Our results show that either proper corrugation or a sharp leading edge can improve the airfoil characteristics—that is, increase the maximum lift-to-drag ratio |(C_L /C_D)_max|. This increase in |(C_L /C_D)_max| is due not to an increase in lift, but to a decrease in drag. Furthermore, this decrease in drag is strongly related to the thickness of the vortex region on the upper surface. These results can explain the advantage of corrugation seen in insect wings and that of the sharp leading edge seen in model-airplane wings.