Experimental study of mass ratio effect on Vortex Induced Vibration of a flexibly mounted circular cylinder

Vortex Induced Vibration (VIV) occurs when a current flows over a bluff (non-streamlined) body. The periodic force caused by vortex shedding can make the body to vibrate. Although VIV is well-known as a destructive phenomenon, but a potential exists to harness this power for generating electrical energy from low velocity currents. In this paper, we study the effect of mass ratio (m* is mass of oscillation body/ mass of displaced fluid) on vortex induced vibration of an elastically mounted circular cylinder over a wide range of Reynolds number (Re= ۱.۸×۱۰۴ - ۷×۱۰۴). The cylinder is limited to transverse oscillation and is carried inside a ۱۴m long water channel. The amplitude of response depends on various parameters such as mass ratio, damping ratio, natural frequency of system, etc. Here we considered ۳ different circular cylinders with the same diameter and length, but distinct mass (m*=۱.۶, ۲.۳, ۳.۴). The experiments carried out in a Towing-Tank water channel and the following results achieved: the peak amplitude of oscillation of the VIV system principally depends on mass ratio. As the mass ratio increases, the maximum amplitude of oscillation and the range of synchronization considerably decreased. For a wide range of velocities, all three cylinders oscillate at the same frequency.

Keywords:

Mass ratio , VIV , Towing-Tank , VIVACE , Ocean Energy