Coherent Flow Structures, Turbulence, and Center of Pressure over Pitching Swept Wings

This study examines the movement of the center of pressure (c.p.) on rigid pitching swept wings using measurements reported in a previous study from the same laboratory. The wings analyzed feature sweep angles of 0, 10, and 20 deg, and they are subjected to large-amplitude sinusoidal pitching instabilities below a critical torsional spring stiffness. The c.p. location is determined from time-resolved force and moment measurements, revealing minimal variation in the cross-chord direction but significant spanwise and chordwise movements, varied by sweep angle. The trajectory of the c.p. varies with sweep angle owing to the evolving strength and dynamics of the leading edge and tip vortices. The force and moment partitioning method is applied to stereo particle image velocimetry 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 flowfield, in influencing the net forces and moments.