Effect of pre-strain and excess length on unsteady fluid-structure interactions of membrane airfoils

Pinunta Rojratsirikul, Zhijin Wang, Ismet Gursul

OAI: oai:purehost.bath.ac.uk:openaire_cris_publications/5353b09d-7969-48a1-98b0-f6a2391b5603 • DOI: https://doi.org/10.1016/j.jfluidstructs.2010.01.005

Aerodynamic characteristics of two-dimensional membrane airfoils were experimentally investigated in a wind tunnel. The effects of the membrane pre-strain and excess length on the unsteady aspects of the fluid-structure interaction were studied. The deformation of the membrane as a function of angle of attack and free-stream velocity was measured using a high-speed camera. These measurements were complemented by the measurements of unsteady velocity field with a high frame-rate Particle Image Velocimetry (PIV) system as well as smoke visualization. Membrane airfoils with excess length exhibit higher vibration modes, earlier roll-up of vortices, and smaller separated flow regions, whereas the membranes with pre-strain generally behave more similarly to a rigid airfoil. Measured frequencies of the membrane vibrations suggest a possible coupling with the wake instabilities at high incidences for all airfoils.