Abstract: The experimental study showcases the aeroacoustic sources measured on a NACA0012 airfoil subjected to dynamic stall due to sinusoidal plunging motions. The flow fields are measured on the upper surface of the airfoil using time-resolved particle image velocimetry (PIV), and the broadband surface pressure fluctuations were measured using a flush-mounted microphone probe and the reconstructed pressure field from PIV. Boundary layer separation occurs as the plunging airfoil approaches the maximum plunging velocity. A dynamic stall vortex (DSV) forms on the upper surface near the leading edge. Pressure distribution over the upper surface evolves in response to the movement of the DSV, with the lowest surface pressure observed at the DSV location. Full boundary layer separation results in a temporary reversal of the adverse pressure gradient, and the lowest pressure during moments of full detachment is at the trailing edge. The overall magnitude of the power spectral density (PSD) of the surface pressure fluctuations increases during the stages near the maximum plunging speed, with greater increases observed for the downstroke phase where the DSV is proceeding over the surface. The low-frequency tonal peaks observed at both the DSV location during downstroke and the maximum velocity during upstroke. However, high-frequency broadband fluctuations were measured from the DSV passage during downstroke. These variations of the surface pressure and its broadband components indicate significant unsteady loading and broadband noise sources from a plunging wing. 

Abstract: Inviscid vortex sheet models provide fast, reduced-order descriptions of fluid–structure interaction by compressing the vorticity into a thin, lower-dimensional interface. For over a century, such models have been used to study unsteady aerodynamic phenomena. Yet their quantitative accuracy relative to the real viscous flows they seek to model has remained uncertain. Here we present a broad and uniform comparison between a single vortex sheet formulation and direct Navier–Stokes simulations across a large collection of plate maneuvers.

By enforcing consistent zero-thickness geometry and carefully resolving numerical singularities in both viscous and inviscid computations, we identify the regimes in which inviscid models accurately reproduce vortex dynamics and force histories, as well as those in which viscous effects are essential. Across most motions considered, the inviscid model achieves 10–20% average relative error. These results clarify the practical limits of inviscid modeling and support its use for the rapid exploration and control of complex unsteady flows.