Hydrodynamic coefficient estimation for TLP and spar structures

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Hydrodynamic coefficient estimation for TLP and spar structures

Lake, M. / He, Haiping / Troesch, A.W. / Perlin, M. / Thiagarajan, K.P.

Research papers at previous OMAE conferences by Thiagarajan and Troesch described forced oscillation model tests using a 0.45-m-dia cylinder and a 0.6-m-disk appended to the cylinder base for drag augmentation. Scaling laws were proposed based on a component scaling concept for extrapolation of full-scale added mass and damping coefficients. The present work further verifies the scaling methodology by presenting and discussing results on smaller models - cylinder and disk of diameters 0.15 m and 0.19 m, respectively. The dimensions of the smaller models are typical of more complex offshore platform models tested in scale 1:50 to 1:75 design sea states. The hydrodynamic coefficients of the cylinder and of the disk are estimated individually, and component-scaling methodology is examined. Physics-based arguments for the differences in force coefficients of the configurations are discussed: flow around the cylinder, flow around the disk, and flow around the composite structure. The analysis results from force measurements and flow visualization conducted during forced oscillation experiments. Further, difficulties in maintaining accuracy with the smaller models are examined.