Scaling the propulsive performance of heaving flexible panels

TLDR

Investigate the propulsive performance of flexible panels actuated by leading‑edge heave oscillations. Use experimental kinematic video, particle image velocimetry, and direct force measurements to characterize the panels. Results reveal that trailing‑edge amplitude and mode shapes scale with Euler–Bernoulli beam parameters, net thrust increases with frequency and peaks near resonances where efficiency is maximized, and the thrust coefficient depends on Strouhal number, with self‑propulsion confined to a narrow Strouhal range and propulsive economy improving at higher flexibilities and lower speeds.

Abstract

Abstract We present an experimental investigation of flexible panels actuated with heave oscillations at their leading edge. Results are presented from kinematic video analysis, particle image velocimetry, and direct force measurements. Both the trailing edge amplitude and the mode shapes of the panel are found to scale with dimensionless parameters originating from the Euler–Bernoulli beam equation. The time-averaged net thrust increases with heaving frequency, but experiences localized boosts near resonant frequencies where the trailing edge amplitude is maximized. These boosts correspond to local maxima in the propulsive efficiency. For a constant heave amplitude, the time-averaged net thrust coefficient is shown to be a function of Strouhal number over a wide range of conditions. It appears, therefore, that self-propelled swimming (zero net thrust) only occurs over a small range of Strouhal numbers. Under these near-constant Strouhal number conditions, the propulsive economy increases with higher flexibilities and slower swimming speeds.