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For truss SPAR platforms, damping plates are employed to increase the added mass and viscous drag in the heave direction. The paper aims to investigate experimentally the hydrodynamic forces on heave plates with different opening sizes. Model scale experiments were carried out on three 40 by 40cm flat plates to investigate the effects of oscillation amplitude and opening size on the hydrodynamic forces acting on the plates whilst undergoing forced heave motion. Three different methods of data processing were investigated, namely, directly processing unfiltered data to obtain the hydrodynamic coefficients, filtering the data before evaluating the coefficients and fitting the filtered data to a sine curve before evaluating the coefficients. The most accurate method was then selected and used to evaluate the experiment results. The coefficient values obtained were compared with the published data available. The effects of various variables such as opening size, KC number, frequency of oscillation on the hydrodynamic coefficients were also studied. Relative magnitudes of the drag and inertia components of the overall hydrodynamic load are compared.

Analysis of model test results was carried out to investigate the hydrodynamic interaction between a pair of elastically-supported rigid cylinders of dissimilar diameters in a water flume. The two cylinders are placed in tandem with one situated in the wake of the other. The diameter of the upstream cylinder is twice as large as that of the downstream cylinder. The spacing between the two cylinders ranges from 1 to 10 times the larger cylinder diameter. The Reynolds numbers are within the sub-critical range. The cylinders are free to oscillate in both the in-line and the cross-flow directions. The reduced velocity ranges from 1 to 10 and the low damping ratio of the model test set-up at 0.006 gives a combined mass-damping parameter of 0.02. It is found that the lift on and the cross-flow motion of the downstream cylinder have the frequency components derived from the upstream cylinder’s vortex shedding as well as from its own vortex shedding, and the relative importance of the two sources of excitation is influenced by the spacing between the two cylinders. The downstream cylinder’s VIV response appears to be largely dependent upon the actual reduced velocity of the cylinder

Analysis of model test results was carried out to investigate the hydrodynamic interaction between pairs of fixed or elastically supported rigid cylinders of dissimilar diameters in a water flume. The two cylinders are placed with one situated in the wake of the other. The spacing between the cylinders ranges from 1 to 15 times the larger cylinder diameter. The Reynolds numbers are within the subcritical range. For the vibrating cylinders which are free to oscillate in both the in-line and the cross-flow directions, the reduced velocity ranges from 1 to 13 and the low damping ratio of the test setup at 0.006 gives a combined mass-damping parameter of 0.02. For the fixed cylinders, the downstream cylinder experiences a drag reduction and it was found that this drag reduction also depends upon the diameter ratio. The lift on the fixed downstream cylinder has the frequency components derived from the upstream cylinder's vortex shedding as well as from its own vortex shedding, and the relative importance of the two sources is influenced by the spacing between the two cylinders. This is reflected in the downstream cylinder's vortex induced vibration (VIV) response which appears to be dependent upon the actual reduced velocities of both the cylinders.