Vortices, turbulence, and center of pressure in flow over pitching swept wings

TL;DR

This paper investigates how vortex dynamics influence the center of pressure on pitching swept wings, revealing sweep-dependent CoP trajectories and applying advanced flow analysis to identify vortex contributions to aerodynamic forces.

Contribution

It introduces a combined experimental and analytical approach using FMPM and stereo PIV to dissect vortex effects on CoP movement in pitching swept wings.

Findings

CoP varies significantly spanwise and chordwise with sweep angle.

Leading edge and tip vortices dominate force and moment contributions.

Flow field exhibits both periodic and stochastic vortex behaviors.

Abstract

This study examines the center of pressure (CoP) movement of rigid pitching swept wings based on prior measurements by (Zhu, Breuer, 2023}. The wings analyzed feature sweep angles of $0^{\circ}$, $10^{\circ}$, and $20^{\circ}$, and are subjected to large amplitude sinusoidal pitching instabilities below a critical torsional spring stiffness. The CoP location is determined from time-resolved force and moment measurements, revealing minimal variation in the cross-chord direction but significant spanwise and chord-wise movement, varied by sweep angle. The trajectory of the CoP varies with sweep angle due to the evolving strength and dynamics of the leading edge and tip vortices. The Force Moment Partitioning Method (FMPM) is applied to stereo Particle Image Velocimetry (PIV) data to identify contributions from wing kinematics, vortex structures, and viscous effects. This approach elucidates the roles of leading edge and tip vortices, as well as the periodic and stochastic components of the flow field, in influencing the net forces and moments.