23rd Offshore Technology Conference, 6-9 May 1999, Houston, TX.
Near-resonant responses of a deepwater platform to wave excitation are controlled by inducing additional hydrodynamic damping in the system. The study used a device designed to induce flow-separation around a vertical column at low Kc numbers. The results of two experimental investigations are presented in this paper. In the first experiment, in-line forces on a 0.3m diameter vertical cylinder were measured without and with the attachment of the flow-separation device. At low Kc numbers the drag coefficients increased by five times due to the attached device to the cylinder, whereas the inertial coefficients were found to be insensitive to the device. The second experiment investigated the wave induced responses of a 8.6m high hydroelastic model of a deepwater tripod tower platform in a 200x12x7m wave tank. A significant reduction in responses at and close to resonance, due to the induced drag damping, observed in the experimental measurements shows that the device is very effective for damping applications. The experimental findings are also supported by analytical results.