Experimental investigation of cross flow - inline coupled Vortex-Induced Vibration on riser with finite length buoyancy module

Vortex-Induced Vibrations (VIV) is a ubiquitous phenomenon caused by shedding vortices behind bluff bodies. VIV induced by ocean currents and waves generates fatigue damage in riser systems. This disturbance creates a big challenge for designing ocean exploration systems. A key feature in determining VIV is the shape and size of the bluff bodies. Therefore, a new design shape, riser section with buoyancy modules of low span to diameter ratio (to serve as weight compensators), requires special attention because hydrodynamic performance is extensively altered in comparison with a bare riser section. A series of extensive forced inline-crossflow VIV experiments on riser models with varying buoyancy module setup were designed and carried out in the MIT Towing Tank. These experiments formulated a new inline-cross-flow VIV hydrodynamic coefficient database for buoyancy module of low span to diameter ratio, which can be included in semi-empirical VIV prediction programs. Several key features of database, including added mass coefficients, lift and drag force coefficients in phase of velocity, etc., were systematically analyzed.