Quasi-steady response of free-to-pivot flat plates in hover

Free-to-Pivot Flat Plates in Hover for Reynolds Numbers 14 to 21,200

“…The St 0.05 and higher Strouhal number cases in Fig. 2 are characterized by a spike in C T and C N , which increases in relative magnitude with increasing St and is associable with the plate completing its rotation near each semistroke extremum and striking its incidence limiter [7]. Plate kinematics (that is, the phase during each semistroke that rotation occurs) is not completely independent of Reynolds number (Fig.…”

“…3 shows that force spikes coincide in t∕T with the point where the plate strikes against its incidence limiter. In other words, the force spike is not centered in t∕T about the midpoint of the plate's rotational motion, and it is therefore not due to the rotation itself [7].…”

“…This allows for large variations in Reynolds number, assessment of Reynolds number effects on vortex formation and shedding, thrust production, and propulsive efficiency. Here, we extend our work on rigid flat plates hinged at the leading edge and oscillated sinusoidally in a water tank [7], to the same motion in glycerin/water mixtures, enabling Reynolds number variations based on plate chord and leading-edge maximum speeds from O10 to O10; 000 to cover the Re 200 computations of Wan et al [4] and Gaston et al [8].…”

“…The test section walls are ≈1.5 chords away from the model. The aspect ratio effect is small, as noted by Granlund et al [7]. To vary the Reynolds number over a larger range than possible with just the velocity and size of the model, the working fluid is a mixture between 100% glycerin and 100% water, giving a chord-based Reynolds number range of 14 to 21,200, respectively, at 25°C [13].…”

The Response of a Single Degree-of-Freedom Wing at Low Reynolds Number

“…a rigid wing with hinges) is limited. Granlund et al 13 examined the response of a wing free to pivot about the leading edge, but constrained in maximum angle, in an oscillating surge hovering motion. The authors observed that allowing the wing to pivot eliminated any evidence of wake capture, and that a quasi-steady assumption was valid.…”