Abstract
An unsteady flow visualization and force measurement were carried out in order to investigate the effects of the reduced frequency of a dragonfly-type model. The flow visualization of the wing wake region was conducted by using a smoke-wire technique. An electronic device was mounted below the test section in order to find the exact position angle of the wing for the visualization. A load-cell was employed in measuring aerodynamic forces generated by a plunging motion of the experimental model. To find the period of the flapping motion in real time, trigger signals were also collected by passing laser beam signals through the gear hole. Experimental conditions were as follows: the incidence angles of the foreand hind-wing were 0° and 10°, respectively, and the reduced frequencies were 0.150 and 0.225. The freestream velocities of the flow visualization and force measurement were 1.0 and 1.6m/sec, respectively, which correspond to Reynolds numbers of 3.4 × 103 and 2.9 × 103. The variations of the flow patterns and phase-averaged lift and the thrust coefficients during one cycle of the wing motion were presented. Results showed that the reduced frequency was closely related to the flow pattern that determined flight efficiency, and the maximum lift coefficient and lift coefficient per unit of time increased with reduced frequency.
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Song Hak Kim received his B.S. degree in aerospace engineering from Korea Aerospace University in 2005. He is currently a graduate student in the Department of Aerospace and Mechanical Engineering at Korea Aerospace University. His research interest is bio-fluid mechanics in the field of aerospace engineering.
Jo Won Chang received his B.S. degree in aerospace engineering from the Korea Air Force Academy in 1982, and his M.S. and Ph.D. degrees from Seoul National University and KAIST in 1986 and 1999, respectively. He is currently an associate professor in the Department of Aeronautical Science and Flight Operation at Korea Aerospace University in Korea. His research interests include unsteady aerodynamics, bio-fluid mechanics, wind tunnel experiments, and flight tests.
Myong Hwan Sohn received his B.S. degree in aerospace engineering from the Korea Air Force Academy in 1977, and his M.S. and PhD degrees from Seoul National University and Georgia Institute of Technology in 1980 and 1986, respectively. He is currently a professor in the Department of Aerospace Engineering at the Korea Air Force Academy. His research interests include unsteady aerodynamics, bio-fluid mechanics, and flow control.
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Kim, S.H., Chang, J.W. & Sohn, M.H. Flow visualization and aerodynamic-force measurement of a dragonfly-type model. J Vis 11, 37–44 (2008). https://doi.org/10.1007/BF03181912
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DOI: https://doi.org/10.1007/BF03181912