An iterative time-marching scheme for the investigation of hydrodynamic interaction between multi-ships during overtaking

An iterative time-marching scheme is developed to investigate the hydrodynamic interactions between multiple ships.Such an unsteady interactive effect could be magnified in restricted waterways,e.g.,a channel or harbor area.To the author’s knowledge,nearly all the research on the ship-to-ship interaction neglecting the free surface effects.The free surface is usually treated as a rigid wall.This assumption is only reasonable when the speed of the ships is very low in deep water condition,due to the hydrodynamic interaction between the ships is mainly induced by near-field disturbances.However,when the moving speeds are moderately higher,especially with a small lateral separation between ships,the far-field effects arising from the ship waves become important.The main objective of the present paper is to develop an iterative time-matching algorithm to solve the hydrodynamic interaction between high-speed ships taking into account the nonlinear free surface boundary condition in time domain.

Research on a Task Planning Method for Multi-Ship Cooperative Driving

A new method for a cooperative multi-task allocation problem(CMTAP) is proposed in this paper,taking into account the multi-ship, multi-target, multi-task and multi-constraint characteristics in a multi-ship cooperative driving(MCD) system. On the basis of the general CMTAP model, an MCD task assignment model is established. Furthermore, a genetic ant colony hybrid algorithm(GACHA) is proposed for this model using constraints, including timing constraints, multi-ship collaboration constraints and ship capacity constraints. This algorithm uses a genetic algorithm(GA) based on a task sequence, while the crossover and mutation operators are based on similar tasks. In order to reduce the dependence of the GA on the initial population, an ant colony algorithm(ACA) is used to produce the initial population. In order to meet the environmental constraints of ship navigation, the results of the task allocation and path planning are combined to generate an MCD task planning scheme. The results of a simulated experiment using simulated data show that the proposed method can make the assignment more optimized on the basis of satisfying the task assignment constraints and the ship navigation environment constraints. Moreover, the experimental results using real data also indicate that the proposed method can find the optimal solution rapidly, and thus improve the task allocation efficiency.