Numerical study on local steady flow effects on hydrodynamic interaction between two parallel ships advancing in waves

Underway replenishment is an essential component of long-term naval operations. During underway replenishment, two ships travel in close proximity at a moderate forward speed. For this issue, frequency domain analysis methods with and without incorporation of local steady flow effects are developed to investigate wave loads and free motions of two parallel ships advancing in waves, which are based on analytical quadrature of the Bessho form translating-pulsating source Green function over a panel or a waterline segment and a direct velocity potential approach. The local steady flow effects were taken into consideration through m-terms in the boundary conditions; meanwhile, the Neumann-Kelvin linear free surface condition was combined. By comparing present added mass, damping coefficient and motion results of Wigley I to those of experiments and other numerical solutions; it is found that present computational results show good agreement. In order to verify these methods for hydrodynamic interaction between two parallel ships, two experiments are carried out respectively to measure the wave loads and free motions for adjacent parallel ship models advancing with an identical speed in head regular waves. Results obtained by the present solution are in favorable agreement with the model tests, meanwhile, results of methods taking the local steady flow effects into consideration show better agreement. Further, the component of wave loads and the interaction effects of speeds and different clearances are deeply investigated. It is found that the effect of clearance and the speed are important factors relating to the interaction effect.