Hydrodynamic Performance Calculation Of The Deep Towed System’s Mother Ship

Deep drag system is the deep-sea geological,geophysical comprehensive observation instrument system towed by the water mother ship with embedded cable along the sea at the height of 10 to 100 meters from the seabed in a slow speed for observation.The mother ship is an important technical supporting platform for submersible vehicle to do resource exploration and scientific investigation,which is a key link of the deep-diving technology system.In order to meet the growing demand,it is necessary to research and develop specialized deep-moving mother ship to ensure the maximum performance deep submergence of the deep submerged vessels.In the process of underwater releasing,recovery and underwater operation,the surface work mother ship will inevitably produce six degrees of freedom movement under the combined action of wind and wave,which will affect the working efficiency and safety of the underwater towing body and the mother ship.And the opening or the moon pool on the ship will increase the amplitude and complexity of the ship’s movement.Therefore,the research on the hydrodynamic performance of the mother ship on the surface has received wide attention by scholars and researchers.Compared with the traditional model test,computational fluid dynamics(CFD)simulation has the advantage of low cost,non-contact flow measurement,which can be used to accurately simulate the ship’s flow field.Therefore,as an effective complement to the model test,the CFD method has been applied more in the hull performance research.At the same time,the validity of CFD method in hydrodynamic performance prediction has been confirmed.The CFD method is used to simulate the flow field of a mother ship with a large opening in the ship according to the main dimensions and hydrodynamic model of the ship.Based on the AQWA software,the hydrodynamic coefficients of the ship with a large opening and original ship are simulated under certain wave motions and wave periods of the hull are analyzed.At the same time,the relationship between the response amplitude operator of the hull and the wave direction of the hull under the action of the regular wave with unit amplitude is given.And the influence of the large opening at the water plane on the hydrodynamic performance of the mother ship at the low speed is calculated.The shape and position of the opening have great influence on the hydrodynamic performance of the mother ship.Two opening schemes and three opening positions are designed in this paper.By calculating the time-domain motion response of the six degree’s freedom under different wave conditions,the optimal opening scheme and the opening position are selected.The underwater releasing and retrieving are restricted by the time-domain motion response of the six degree’s freedom,the time-domain numerical analysis is carried out on the surface mother ship under the combined action of wind and wave,and the six-degree-of-freedom motion response of the hull under different wave conditions is obtained.And the sea condition of the underwater needed by the normal releasing and retrieving operation is given according to the response,and the influence of the operation on mother ship’s response during the towing process is calculated and analyzed.