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Session: PIV/PTV methods and applications IV
Session starts: Thursday 06 November, 11:00
Presentation starts: 11:00
Room: Lecture room A

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Qin-Feng Guo (Fluid Mechanics Key Laboratory of Education Ministry, Beihang University, Beijing, China)
Jin-Jun Wang (Fluid Mechanics Key Laboratory of Education Ministry, Beihang University, Beijing, China)

Abstract:
This paper develops a high-speed synchronous measurement system, including high accuracy three-dimensional deformation measurement (HADM), Particle Image Velocimetry (PIV), and a force transducer. The system is applied to investigate the fluid–structure interaction of a square flexible membrane wing with a sampling frequency of 1100 Hz. The membrane's three-dimensional deformations, mid-span flow fields, and lift fluctuations are examined at an angle of attack of 8° and a Reynolds number of 8.2 × 10^4. The membrane exhibits a second mode vibration along the streamwise direction, with a dominant frequency of 135.8 Hz. It is newly observed that two leading-edge vortices (LEV1 and LEV2) are formed above the membrane as the lift increases from its minimum to maximum value. LEV1 sheds from the leading-edge shear layer, while LEV2 remains attached to the wing surface. When LEV1 and LEV2 coexist above the wing surface, the lift reaches its maximum value.