Experimental and Numerical Studies of Vortex Induced Vibration on Cylinder

Study of vibrations due to vortex shedding (VIV) in the wake of a cylinder that is exposed to current or oscillatory flow is very important, especially for marine risers which are used to extract oil  and gas from the sea bed. The phenomenon of vortex induced vibration (VIV) has been one of the major concerns for hydrodynamic researchers due to its potential ability to cause severe fatigue damage. The hydrodynamics of VIV is very complex and still not fully understood. In this paper, some results (amplitude over diameter, lift and drag coefficients) of high Reynolds VIV experiments that are performed in UTM towing tank with an in-house test set-up are presented. A circular cylinder of 114 mm in diameter and 3 min length was towed at constant speed through the basin at Reynolds numbers up to 1.1x105. Model tests with a stationary cylinder and tests with a freely vibrating cylinder were carried out to investigate the influence of VIV on drag coefficient. Later these results are compared with results obtained through 3D numerical simulation, LES is used to solve turbulence flow. It was found that CFD results showed similar trends with experimental results. Results of this paper can be very important to design riser system  and future endeavor  to perform  similar kind of experiments. Successful numerical study of the VIV can also be fruitful for designing efficient VIV suppression devices.