General And Acoustic Characteristics And Performance Optimization Of Submarine With Non-revoluting Form

The technology of traditional submarines with nearly cylindrical revolutionary form has been developed and employed for about a century,resulting in the relatively mature technology.In the past half a century the technical development of the traditional form submarine is mainly focused on steadily improving the combat operational performances,and more importantly the stealth behavior.In design of a submarine its geometric form,pressure hull arrangement,principal particulars,displacement,propulsion and power configurations etc.are closely related with each other.To some sense the motion,safety and stealth performance of a submarine would be greatly restricted by its geometric form and pressure hull arrangement.To raising the capacity of ocean territory defense,military power,ocean resource exploration and exploitation,the missions and tasks of newly developed submarines are extended from solely combat operations to multi-functional tasks.The corresponding technologies are also further promoted,leading to variations of the geometric form and pressure hull arrangement of the vessel.The previous preliminary study at home and abroad shows that the submarine with flat non-revolutionary form exhibits some technical advantages,for example better stealth performance,deeper submergence,more stable navigation,multi-loads storage capacity outside the cabins,safer operation near sea-bed in floating or landing,and suitable for multi-functional defense in offshore shallow sea.Therefore,in the past more than two decades the research on technologies of new concept submarines with bionic non-revolutionary flat forms has been carried out in some countries.Part of the technologies has been applied in some unmanned submersibles.Even some of the existing submarines also adopted the non-revolutionary form to meet their specific functional requirements.Drawing inspiration from the high swimming performance and low radiation noise of marine fishers,it is expected that the technology of bionic non-revolutionary flat form submarine may lead to a stride-over promotion of future submarine behaviors.Thus the corresponding technology has become an important research direction for manned and unmanned underwater vehicles.However the non-revolutionary multi-hull submarines may have variety of possible geometric forms and pressure hull configurations,which would be much more complicated comparing with the traditional submarines with nearly cylindrical revolutionary form.Up to now,there is lack of research on hydrodynamic performances and acoustic behaviors of such kind of non-revolutionary multi-hull submarines.It is therefore of special importance to explore the differences of the hydrodynamic,structural and acoustic performances and characteristics of this kind submarines with respect to those of the traditional submarine,even if in the investigation the formers are only of simplified non-revolutionary form and two or three stiffened cylindrical pressure hulls.In view of the above mentioned background and purpose,this thesis takes the multi-hull non-revolutionary submarines as the research objects,mainly deals with three aspects: the mathematical expressions and parametric modeling of their geometric forms,analyses of their hydrodynamic performances and acoustic characteristics,and optimizations of the geometric and structural paramdeters to achieve the best performance.The specific contents are as follows:(1)The characteristic geometric parameters describing the hydrodynamic profiles of the flat twin-stern non-revolutionary submarines are defined,and the mathematical expressions for parametric modeling of the hydrodynamic profiles are derived and the corresponding software are produced.This provids an useful tool for automatic modeling of hydrodynamic performance calculation and optimization.The parametric FEA-model creation program is also provided for structural radiation noise analyses of the multi-hull submarines.(2)The characterization factors and methods of the geometric features and the resistance properties of the non-revolutionary submarines are introduced.Employing the commercial CFD software,the surrounding flow velocity fields and the fluid resistance variations of the non-revolutionary submarines advancing in constant velocity with regard to different flatness(the beam to height or diameter ratio)are calculated,and the corresponding characteristics are summarized.By solving the maneuverability equations with the hydrodynamic coefficients of the derivative terms obtained by model tests,the manoeuvring characteristics of stable rotating motion,the influences of different stern profiles and manoeuvring surface layouts on the rudder efficiencies and stern fluid fields are simulated and compared.(3)In the condition of same displacement in water,choosing different design submerging depths,different flatness or diameters,and different materials of the pressure hulls,the detailed structural parameters of the non-revolutionary submarines with single,twin and triple cylindrical shells are defined based on the classical strength and stability theories of stiffened cylindrical shells.Their structural acoustic radiation behaviors excited by concentrated force are calculated and discussed.The acoustic radiations of single pressure hull or twin pressure hulls assembled by joining plates,all attached with light envelopes,are calculated when the excitations are sinusoidal longitudinal or lateral unit forces acting at each stern.The results exhibit that the increase of the design submerging depth can efficiently increase the structural stiffness,reduce the radiation noise,hence improve the stealth property.When excited by sinusoidal longitudinal unit force at the stern,the radiation noise levels of the non-revolutionary submarines with twin or triple cylindrical shells are less than that of the submarine with single cylindrical shell.(4)By employing the measured structural vibration and acoustic radiation data of an underwater segment model with triple cylindrical shells and light envelope,the prediction method of the acoustic properties of a flat multi-hull structure is validated.(5)The relationships between the characteristic geometric parameters and the hydrodynamic resistance or the radiation noise are obtained by regressions of the calculated data.The contribution levels of different characteristic geometric parameters to the resistance coefficient are also analyzed.The methods and corresponding models for optimizations of resistance and structural acoustic radiation properties of the non-revolutionary submarines are established.The towing tank resistance tests of two models with the optimized and original hydrodynamic profiles respectively of a non-revolutionary submarine were carried out to verify the optimization results.Although the present thesis has greatly simplified the hydrodynamic profiles(geometric forms)and pressure hull arrangements to investigate the hydrodynamic performance(resistance and maneuverability)and the concentrate-force excited structural acoustic radiation behaviors of multi-hull submarines with flat non-revolutionary form,the proposed methods and results are hopefully of great help to better understand the hydrodynamic performance characteristics and structural acoustic radiations properties,as well to provide useful scientific references for design and optimization of such kind of submarines.