Analysis Of Hydrodynamic Characteristics Of Towed Body Controlled By Multiple Control Mechanisms

Towed body is a kind of working platform which is widely used in underwater exploration at present,and its main trajectory and attitude control mechanism is ducted propeller and forced hydrofoil.In the process of underwater control of towed body,the interaction between these control mechanisms and the main body of underwater towed body makes the flow field around it change complicated.In the field of studying the hydrodynamic coupling relationship between the main body and the components of underwater towed body,there are still many topics worthy of further exploration.Through CFD and other means,the hydrodynamic characteristics of the towed body under the control of a variety of control mechanisms are simulated accurately and effectively,which is of great engineering significance for the development and design of a new type of underwater trajectory control towed body with excellent performance.The main work of this dissertation is to study the hydrodynamic characteristics of the vertical airfoil main body underwater towed vehicle developed by our research group on STAR-CCM + platform by using different numerical techniques under four typical operating states: Firstly,the superimposed mesh technique is used to simulate the hydrodynamic characteristics of the forced sinking hydrofoil and the towed body of the "forced sinking flap + fixed horizontal wing" towed body when the forced sinking flap oscillates sinusoidal in the range of 30° Angle when the ducted propeller is not rotating.Secondly,by comparing the flow field characteristics of the forced hydrofoil towed body with independent controllable angle of attack,its forced hydrofoil swings sinusoidal law in the range of 30° Angle,further analysis shows that the fixed horizontal wing is set as the depth control of the towed body to achieve the effect of energy saving;Then,the flow field characteristics of the towed body during the periodic bow turning motion were studied by using the overlapping nested sliding mesh technique under the condition that the forced sink flap was fixed horizontally and the steering vessel propeller changed periodically at a certain speed.Finally,taking the single-dimensional motion as the control group,the grid technique of "global overlap nested local overlap + local slip" was used to simulate the hydrodynamic characteristics of the heaving coupled bow turning motion of the towed body under the condition that the forced flap oscillates sinusoidal in the range of 30°angle and the left and right ducted propellers rotate alternately at a certain speed.Through the comparison of the mechanical characteristics,the influence of the control actions of the control mechanism such as forced sinking flaps and turning bow steering guide propellers on the overall flow field characteristics of the towed body system is obtained.The results show that :(1)The dynamic response periods of the main components of the towed body are induced by the control force emitted by the control mechanism,and their mechanical modal change periods are consistent;(2)The depth control effect of the control mechanism composed of "forced sinking flap + fixed horizontal wing" is better than that of the independent controllable Angle of attack forced sinking hydrofoil;(3)The grid technique of "global overlap nested local overlap +local slip" can be used to simulate the dynamic state of the towed body efficiently and practically in the joint operation of multiple control mechanisms.(4)Under the heave coupled heading movement controlled by multiple control mechanisms,the towed body can move in a larger range on the horizontal plane,but the depth range it can reach is limited.The numerical calculation method adopted in this paper solves the problem of complex flow field information data exchange under the interaction between the forced sinking flap,the forced sinking hydrofoil with independent controllable angle of attack,the steering vessel propeller and the towed body in the numerical simulation.In order to analyze the hydrodynamic relationship between the towed body + forced hydrofoil + ducted propeller under the combined control mechanism of underwater towed body coupled motion,an operable solution is proposed.