Affiliations: Osaka Science & Technology Center, 1-8-4
Utsubohonmachi, Nishi-ku, Osaka 550-0004, Japan. | Department of Mechanical Systems Engineering, Kyushu
Institute of Technology, 680-4 Kawazu, Iizuka, Fukuoka 820-8502, Japan.
Abstract: Two-dimensional flow patterns have been visualized by two kinds of
dyes and a VTR camera in a water tunnel at Re = 4.0 ×10³ in order to
study how flow patterns of vortex changed behind a pitching airfoil with
various pitching rates and pitching amplitudes. The tested airfoil was
NACA0010. The experiment was performed under the conditions such as the
pitching motions with sinusoidal or triangular wave around its mid- or
quarter-chord axis. The non-dimensional pitching rates were k = 1.97, 2.81 and
4.22. The pitching amplitudes were changed as A = ±2·,
±6· and ±12·, however the mean angle of attack was
fixed at α_m = 0·. As a result, the followings were clarified. The
flow pattern of thrust producing vortex street was observed in the wake behind
the pitching airfoil with a higher non-dimensional pitching rate. Similar flow
patterns of the vortex were observed in spite of the differences in the
location of pitching motion axis, in the pitching motion wave profile and in
the pitching amplitude. Moreover, the pitching motion around the quarter-chord
axis with triangular wave could realize the thrust producing vortex street more
easily.