Modeling of Pitching and Plunging Airfoils at Reynolds Number between 1×10 4 and 6×10 4

Fluid physics associated with a pitching and plunging airfoil, while critical to the development of flapping wing air vehicles, is not adequately understood. To help assess the state-of-the-art of engineering predictive tools, we utilize recently obtained experimental information based on particle image velocimetry (PIV) in a water tunnel from two different facilities to examine the effects of chord Reynolds number, and the airfoil shape on the associated flow structures. Two rigid airfoils, SD7003 and flat plate, undergoing pitching and plunging motion in nominally two-dimensional conditions are investigated with the aid of the original Menter’s Shear Stress Transport (SST) turbulence model and a modified version which limits the production of turbulence kinetic energy to reduce the build-up of turbulence in stagnation regions. We consider two kinematic schemes, a pitching and plunging, and a pure plunging motion. For the SD7003 airfoil under pitching and plunging motion, the original SST model offers consistently favorable agreement with both PIV measurements. For the pure plunging SD7003 airfoil case, depending on the turbulence characteristics including those caused the motion of the wing, and the implied eddy viscosity level, qualitatively different flow structures are observed experimentally and computationally. The flat plate creates flow fields insensitive to the Reynolds number, and quite different from those around the SD7003 airfoil, due to the leading edge effect.

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