Experimental Investigation on Lift Coefficient for a Truss SPAR Subjected to Vortex Induced Motions

摘要

The prediction of lift coefficient of Truss Spars is the base for investigating added mass coefficient and damping coefficient, which are important in the estimation of fatigue damage rates. The 1:60 scale Truss Spar model tests have been conducted in towing tank at Zhejiang Ocean University (ZOU). The Truss Spar model consists of a hard tank with removable helical strakes, a truss section and a square soft tank. Model tests were carried out with simplified mooring system. In this study, results from the experiment subjected to uniform current were reported. The Reynolds numbers varied from 8E04 to 2E05. The lift coefficient, lift coefficient components in phase with velocity and acceleration and the phase angle were calculated. The results showed that the symbol of the lift coefficient in phase with velocity varied with the reduced velocity, while the lift coefficient in phase with acceleration was negative at the investigated range of reduced velocity. The magnitude of lift coefficient in phase with acceleration decided the magnitude of the lift coefficient. The symbol of phase angle varied with the reduced velocity, which was in agreement with the symbol of the lift coefficient in phase with velocity.