Comparison of floating structures motion prediction between diffraction, diffraction-viscous and diffraction-Morison methods

Abstract

This research is targeted to improve the accuracy of diffraction potential theory to predict semi-submersible heave motion response by considering the drag effect in the prediction. From both the numerical and experimental studies, it can be observed that the diffraction potential theory is not predicting well the semi-submersible heave motion response when the motion is dominated by damping. In this research, the viscous damping correction method and Morison equation drag correction method are applied to improve the motion response predicted by diffraction potential theory. This paper will briefly present the procedure to integrate the viscous damping correction method or Morison equation drag term correction method with the diffraction potential theory. The proposed numerical methods are applied in this research to simulate the semi-submersible heave motion response. After that, all simulation results are compared to the experimental result from tests at the same wave condition to validate the proposed numerical methods. From the comparison, it is concluded that Morison equation drag correction method is able to estimate the semi-submersible heave response in the damping dominated region and provides more reasonable motion tendency compare to other methods.