Flow characteristics of translating flexible wings at low reynolds numbers

Yazdanpanah, Mahdi
This study experimentally investigates the flow field around surging-translating wings that are started from rest and compares the flow field characteristics with that of surging-revolving wings. Three wings with different level of chordwise flexural stiffness (i.e., highly flexible, moderately flexible and rigid) were studied. The experiments were performed in an octagonal water tank at the Reynold number of 7360 based on the terminal velocity of 0.08 m/s, and the wing chord length of 92 mm. Two-dimensional two-component particle image velocimetry (2D2C PIV) technique was employed to obtain the planar flow fields at the 75% of wingspan position. The PIV measurements reveal a coherent leading edge vortex at the initial phases of the translating motion for all of the wings considered in the study. After approximately two chord lengths of travel, the LEV bursts in the rigid and moderately flexible wings, whereas for the highly flexible wing the LEV preserves its coherency for a longer period of motion. The comparison of flow fields between the translating and the revolving motion kinematics reveals similar behavior of the vortical structures yet the LEV circulation in the translating wings has higher values. The LEV centroid in the revolving cases stays above the leading-edge, while in the translating wings, it always remains at a lower position. The effect of high flexibility results in the retention of LEV closer to the wing surface for both translating and revolving cases.


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Karakaş, Hasan Halil; Perçin, Mustafa; Department of Aerospace Engineering (2022-8-12)
This study experimentally investigates the flow field around the wings, which first accelerate with constant acceleration from the rest and then perform a linear translating motion with constant velocity. Four wings, which are 3D-printed, with a bending stiffness in different directions are examined. The difference in bending stiffness values is achieved by placing stiffeners having different angles with the leading edge on the upper surface of the wing. The stiffeners are printed with wings to obtain well-...
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This study explores the effects of rotational mechanisms on the characteristics of the leading edge vortex (LEV) by comparing translating and revolving flexible wings that are started from rest. Tomographic particle image velocimetry (tomographic-PIV) technique was employed to acquire three-dimensional flow fields for the revolving wings, while planar flow fields for the case of translating wings were acquired via 2D2C-PIV measurements. The comparison of flow fields between the two motion kinematics reveal...
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Çekinmez, Aybüge; Alemdaroğlu, Hüseyin Nafiz; Department of Aerospace Engineering (2013)
In this thesis, the vortex shedding formation/mechanism for flapping airfoil making the figure of eight motion in hover is investigated experimentally using Particle Image Velocimetry (PIV) technique and numerically for some parameters determined. For this investigation, a new flapping mechanism is designed and implemented to the existing water tank, where the airfoil is traversed laterally, such that the motion depicts a figure of eight. The traversing system is moved both in x (horizontal) and y (vertical...
Citation Formats
M. Yazdanpanah, “Flow characteristics of translating flexible wings at low reynolds numbers,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Aerospace Engineering., Middle East Technical University, 2019.