Three-dimensional flow and load characteristics of flexible revolving wings at low Reynolds number

Abstract

This study explores the flow field and fluid-dynamic loads generated by revolving low-aspect-ratio flat plate wings undergoing a revolving motion starting from rest. Three wings with different degree of chordwise flexural stiffness (i.e., rigid, moderate flexibility and high flexibility) have been tested in order to investigate the influence of the wing flexibility. The wings have an angle of attack of 45 deg in their undeformed condition. The measurements have been performed in a water tank at a Reynolds number of 10,000 based on the chord length and terminal velocity at the 75% span position. The experimental campaign consists of phase-locked tomographic particle image velocimetry measurements complemented with simultaneous force measurements The three-dimensional velocity fields are captured in three measurement volumes positioned side-by-side along the span of the wing for different phases of the revolving motion, generating a time-resolved volumetric velocity field data set. Subsequently, from the velocity data the pressure fields are reconstructed as well as the loads acting on the wing.