Evolution of wake structure and wake-induced loads along the path of freely rising axisymmetric bodies

This paper reports on the zigzagging motion of disks of various thicknesses rising freely under the effect of buoyancy in a liquid otherwise at rest. Time sequences of the velocity fields around the moving body were obtained using particle image velocimetry and are presented for two bodies with contrasted diameter-to-thickness ratios. The differences observed between the two cases are discussed in relation with the evolution of the loads acting on the body and of the displacement and rotation of the body during a period of the zigzag. The crucial influence of the phase difference between the vortical force and torque on the path is underlined.