Connection Between Vortex Structures and the Center of Pressure in Unsteady Separated Flow Over Pitching Swept Wings

This study examines the center of pressure (CoP) movement of elastically mounted, rigid swept wings based on prior measurements by Zhu and Breuer [1]. The wings analyzed feature sweep angles of 0◦, 10◦, and 20◦, 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.