Previous numerical investigations conducted by authors have found that two different regimes of heave damping forces experienced by a TLP column during "springing vibration" generally exist depending on Keulegan Carpenter number and frequency parameter range. Significant effect of a small corner radius (2~ of cylinder radius) at the cylinder bottom edge on the form drag has been found for a fixed oscillatory frequency (0.41 Hz) over the Keulegan Carpenter number range investigated. The present paper has further investigated the effects of the corner radius of a TLP column on the springing damping forces. It is found that the corner radius in general reduces the form drag exerted on the oscillatory cylinder, and the reduction is larger as corner radius increases. Two different heave damping regimes (linear and non-llnear) also exist, and the transition from llnear to non-Hnear damping regime is delayed due to the corner radius at the cylinder bottom edge.
There are many instances in offshore engineering where the hydrodynamic damping forces are appreciable for the structure to reduce the undesired motion as soon as possible. For example, damping force is favourable and also crucial to reduce the excessive load exerted on the tethers of a Tension Leg Platform(TLP) experiencing high frequency "springing vibration" in the vertical plane. So a TLP column is normally designed with a sharp bottom edge in order to gain a large hydrodynamic damping force in the vertical plane motions. However, in the offshore practice, the edge of a TLP column can rarely be kept exactly sharp in the marine environment. For instance, the sharpness of the edge could be changed by marine fouling. Therefore the corner radius effect must be carefully taken into account in the design stage of a TLP.
