A Comparison of Seakeeping Predictions for Wave-Piercing Catamarans Using STF and URANS Methods

Wave-piercing catamarans (WPC) consist of two demihulls with wave piercing bows that may pitch to immerse into or emerge out of the free surface when advancing in waves. So linear theories like STF are questionable to precisely predict the seakeeping performance of WPC in general cases. In this paper, URANS-based solver and STF method are employed to predict the pitch and heave motions of WPC for various speeds and wave frequencies in head seas. Furthermore, some extending studies, such as modifying the shape of wave piercing bows, disregarding the interaction between demihulls, and neglecting the viscosity of water, are also carried out using the URANS-based solver. Comparison of numerical and experimental results shows that under the Froude numbers of interest (0.3 < Fn < 0.6) good agreement is achieved by using the URANS-based method, while only similar trend is obtained by using STF. Based on numerical results, it could also be concluded that the forward speed effect on the free surface is significant, while the viscous effect is unimportant for the motions.