CFD prediction of stern flap effect on Catamaran seakeeping behavior in long crest head wave

Abstract

The paper presents the numerical studies of seakeeping behavior for a high-speed catamaran with stern flap advancing in long crest head wave. Both model-scale and full-scale simulations have been carried out in sea state 6 using unsteady Reynolds-averaged Navier-Stokes (URANS) solver. Uncertainty analyses were performed to verify the accuracy of the numerical solver. Model tests were conducted for the catamaran including resistance tests in calm water and seakeeping tests in regular waves to validate simulation results. The comparisons between simulation results and experimental results show good agreement. Seakeeping behaviors of models with/without stern flaps were predicted for the comparison and evaluation. Model-scale simulation results indicate that using stern flap could reduce catamaran's total resistance and the effects on heave and pitch motions are obvious in sea state 6. The installation of stern flap shows significant effect on the reduction of vertical acceleration's amplitudes, especially for reducing the occurrence of slamming impact due to the effective control of model's trim angle. Full-scale simulations have also been conducted and compared with results at model scale. Results show that effects of stern flap on heave and pitch motions are the same for both model-scale and full-scale catamaran. Residuary resistance coefficients on full-scale catamarans with/without stern flap are almost the same with model-scale simulations.