Near-wake aerodynamic characteristics of a radially deforming circular cylinder using LDV measurements

An experimental study is carried out to develop a strategy for a circular cylinder near-wake control. The technique being used consists of a 5% radial deformation of the cylinder cross-section according to a sinusoidal law. In practice, this is achieved using a set of cams with suitable variable radius following a defined profile. For a Reynolds number of 3.52 × 103, six values of radial deformation frequency, around twice the natural vortex-shedding frequency, are considered, in addition to the natural case. The velocity longitudinal component is examined via LDV. Remarkable changes are noticed for various aspects of the flow. The well-known “lock-in” phenomenon is observed for deformation frequencies close to twice the natural vortex-shedding frequency. The near-wake is characterized by an accelerated flow in the recirculation bubble as well as an important reduction of both the recirculation bubble and vortex formation lengths. It may also be noticed also that the drag coefficient is approximately reduced by a ratio of 46% close to the “lock-in” range.