Numerical and experimental study on the scale effect of internal solitary wave loads on spar platforms

Based on laboratory experiments and numerical simulations, the scale effect of Internal Solitary Wave (ISW) loads on spar platforms is investigated. First, the waveforms, loads, and torques on the spar model at a laboratory obtained by the experiments and simulations agree well with each other. Then, a prototype spar platform is simulated numerically to elucidate the scale effect. The scale effect for the horizontal forces is significant owing to the viscosity effect, whereas it is insignificant and can be neglected for the vertical forces. From the similarity point of view, the Froude number was the same for the scaled model and its prototype, while the Reynolds number increased significantly. The results show that the Morison equation with the same set of drag and inertia coefficients is not applicable to estimate the ISW loads for both the prototype and laboratory scale model. The coefficients should be modified to account for the scale effect. In conclusion, the dimensionless vertical forces on experimental models can be applied to the prototype, but the dimensionless horizontal forces of the experimental model are larger than those of the prototype, which will lead to overestimation of the horizontal force of the prototype if direct conversion is implemented.