Abstract: The flow in turbulent boundary layer and the viscous drag over V-groove surface are numerically simulated using the RANS formula and RNG k-e turbulence model. The influences of the tip shape of V-groove and Reynolds number on the drag reduction effect are studied; and the mechanism of drag reduction effect is analyzed, too. It is shown that, the smaller the fillet radius of the tip is, the better the effect of drag reduction is. As the fillet radius of the tip becomes smaller, the wall shear stress on the middle and low part of the groove surface becomes less, but the local wall shear stress on the tip becomes greater; the flow velocity has a great influence on the ratio of drag reduction, and the favorable flow velocity range is related to a certain groove dimension, hut the locations where the groove surface is set along the flow direction have very little influence on the ratio of drag reduction, while the dimension of groove has very strongly influence on the drag reduction effect. The secondary vortices generated at the groove peaks are the fundamental reasons of the drag reduction, and the drag reduction ratio is closely related to the intensity of the second vortex.

Abstract: Modeling is a vital precondition to evaluate ship maneuvering performance and controllability. System identification based on free-running model tests is one of the methods to obtain the hydrodynamic coefficients in mathematical models of ship maneuvering motion. In this paper, an identification method for determining the response models of maneuvering motion by using support vector regression (SVR) is presented. The proposed method uses analytic parameter regression from training samples obtained in free-running models tests. The results of estimation and simulation demonstrate the validity of the identification algorithm for conventional surface ships.

Abstract: A procedure of Multidisciplinary Design Optimization (MDO) is applied to design of a submarine system which is large and complex enough to require that the design problem be decomposed to a set of tractable design problems carried out by disciplinary specialistsA multidisciplinary decomposition and Analyses were developed for this complex system that includes hydrodynamics, propulsion, weight, performance and cost The collaborative optimization (CO) architecture is selected to conduct the preliminary conceptual design of submarineThis approach was able to identify feasible designs with the basic construction cost reductions relative to baseline designThe results also demonstrate MDO approaches more suitable for design of the submarine and more flexible and advanced compared with the traditional design approach

Abstract: Hydrodynamic noise is an important noise source of submarine and underwater vehicles when they are cruising at a high speed.Generally,when the Ma number is low,the hydrodynamic noise is mainly radiated by vibrating elastic structures excited by wall-pressure fluctuations beneath turbulent boundary layers(TBL).In this paper,the progress of researching the frequency-wave number spectrum models and the measurement methods of wall-pressure fluctuations beneath TBL were chiefly introduced.And the calculation of acoustic radiation of elastic structures excited by wall-pressure fluctuations beneath TBL is presented.

Abstract: Liquid sloshing phenomenon in a liquid tank mounted on ship has caused people's profound attention and the sloshing loads and effects have become the important content of the safety evaluation of a sailing liquid cargo.In this paper,numerical simulation of liquid sloshing in a rectangle liquid tank forced sway and rolling is performed based on Level-set method.The elevation of free surface and the pressure time history are obtained.The results show that the Level-set method can be used to simulate liquid sloshing effectively.

Abstract: The present design status of the spherical pressure hull in the deep-sea manned submersible was reviewed and the characteristic of the spherical hull of 6 000m class manned submersible was comparedThe design thickness and weight characteristics of the Titanium alloy spherical hull were given by plastic analysis method and the design factors including the safety factor,inner diameter,volume density and weight of the spherical hull were discussed

Abstract: The flow around submarine operating close to the bottom or near surface were numerically simulated by solving RANS equations with RNG k-e turbulence model.The resistance,vertical force and pitching moment of a submarine model at different depths of bottom were computed.And the change of resistance with Froude number was studied.It indicates that the bottom has a neglectable effect on resistance as long as the depth of bottom more than 1/2 submarine length.Free surface was captured with VOF(Volume of Fluid) method.So the resistance and wave pattern of a submarine model at different depths of submergence were computed.And the change of resistance and wave pattern with Froude number were investigated.It indicates that the free surface has a neglectable effect on resistance and wave pattern as long as the depth of submergence more than 1/3 submarine length.The comparison between the prediction and the model test measurement shows fairly good agreement.

Abstract: According to the pitting corrosion mechanism and corrosion data from ship structure investigated,the shape of corrosion pits and its formation on ship structures were surveyed and summarized in this paperIt was shown that the main pits shape may be cone or compound-coneObviously,the shape of corrosion pits on ship structures was affected by its locations and ship ageThe shape difference between those two pits type was resulted from the divergence in their corrosion-control factors and their influencing degreeIt will be reasonable to describe the ratio of diameter to depth of corrosion pits as a function of ship ageThe time dependent model of pits ratio was also established in this paper,based on the model of corrosion pits depth and the corrosion data of hold frames in cargo holds from literatures

Abstract: The deficiencies that exist in the current theoretical methods to predicate longitudinal motion of planing craft are analyzed.According to craft's formal characteristics and model tests of planing crafts in still water,regular wave and irregular wave,some fundamental assumptions of longitudinal motion of planing craft are presented;the longitudinal motion equation of planing craft is established,which includes the effects of the planing lift and the planing lift moment;a suitable method to predict the longitudinal motion of planing craft is developed,and the theoretical prediction program is set up.Three calculation methods—the full displacement method which ignores the changes of configuration of craft at navigation,the floating method which only includes the effects of configuration of craft at navigation and the planing method which includes the effects of configuration of craft at navigation,planing lift and planing lift moment—are compared with each other.The result shows that the full displacement method and the floating method are suitable at low speed of the craft,while the planing method should be applied at middle or high speed of the craft,to predict the longitudinal motion of planing craft.

Abstract: The reliability analysis of ship structures considering corrosion in recent years is reviewed.By this summarization,it is found that the emphasis of this research field have converted from general corrosion to localized corrosion,especially,the pitting corrosion.The important aims of the future work may be as follows:first,developing the new pitting corrosion model which will be more precisely to predict the statistical characteristics of corrosion wastage of ship structures;next,studying the ultimate strength of corroded structural components under various loads,to find out the main influencing geometry parameters of pit;third,evaluating the reliability of ship structures considering the interaction between corrosion and fatigue.

Abstract: Based on the NURBS representation of the ship hull surface and deck, polyhedron representation of the inner bottom shell, the efficient plane-surface intersection algorithm and the geometric properties calculation method, the virtual subdivision and hold capacity calculation method for arbitrary shapes of compartments are presented Twelve kinds of compartment shapes are defined according to the geometric elements (bulkheads, deck, ship hull or inner bottom shell) constructing them The hold capacity can be calculated and virtual subdivision realized with the offset information of the ship hull, bulkheads position or knuckle points of them and the folding points position of the inner bottom shell as the only inputs, avoiding the fussy input of the tank's offset so as to decrease the heavy operation and increase the design quality The hold capacity curves, at any 3D inclining surface, can be calculated This precise and concise method is convenient to the 3D parametric design of ship

Abstract: A numerical procedure is developed to predict the steady and unsteady performances of ducted propeller with stators,in which a potential based panel method is applied for the flow around propeller together with hub,duct and stators respectively.The interaction among them is treated in an iterative manner.To facilitate the computation,circumferentially averaged values of the induced velocities are adopted to consider the steady hydrodynamic interaction among propeller,duct and stators.The unsteady hydrodynamic interaction among them is solved by an iterative method in the time domain.In addition,a simplified method for the unsteady interaction of vortex shedding among propeller,duct and stators is proposed to reduce the computing time without the loss in the precision.Programs for the propeller,stators and duct are run by turns until convergent results of hydrodynamic forces for each part are obtained.Numerical calculations are conducted for some examples.Comparisons of the numerical results with the experimental data show good agreement.

Abstract: The effect of parameters selected in the numerical simulation of natural cavitation and supercavitation based on Fluent62 code is studiedDifferent mass fractions of non-condensable gas nuclei are set to simulate cavitation flow around an axis-symmetrical body with hemispherical nose in order to find out the effect of nuclei on cavitation flowWhen supercavitation flow around an axis-symmetrical body with flat nose is simulated,different values of turbulence intensity are set on the boundary condition for studying their influence on cavitation flow regionAccording to the calculation results of supercavtation flows around a disk cavitator,it can be concluded that the value of mass fraction of gas nuclei mainly affects the profile of the tail part of supercavity and the value of turbulence intensity mainly affects the size of the supercavityCalculation results show good agreement with experimental results and available empirical equations

Abstract: A two-dimensional Reynolds-averaged Navier-Stokes(RANS) code equipped with SST k-ω turbulent model is applied for elastic mounted cylinder with low mass-ratio moving under stream-wise and transverse motion.Different mass-ratios are calculated to obtain a critical mass-ratio m=3.5 below which lager transverse amplitude can be yielded for elastic mounted cylinder with two degrees of freedom rather than one degree of freedom.Numerical results are compared with recent experiment's results in detail in the paper.

Abstract: As the complexity of ship structural designs keeps on increasing, the use of statistical techniques to build approximation models for expensive computer analysis is getting popular. In this paper, three commonly used approximation methods for multidisciplinary design optimization (MDO) of complex engineering systems, including response surface modeling, Kriging and radial basis function network,are reviewed briefly and compared through two case studies. The sample points are selected by a series of randomized orthogonal arrays.Error analysis is then performed to measure the accuracy of the approximation models.Besides the traditional quadratic response surface,fully three-order polynomial response surface models are also constructed for the comparison.It is found that Kriging model is much more suitable for MDO of ship structures than other models for its high accuracy and stability.

Abstract: Corrosion is one of the main reasons which causing structure failure and damageFor mild and low-alloy structural steels under marine immersion conditions,the main influencing factor and the specific process of pitting corrosion were summarized in this paper,according the pitting corrosion mechanics and various corrosion data from some long-term field investigationsThe new maximum pit-depth model described by weibull-function was also given here,which will be more precisely to predicting the statistical characteristics of maximum macro-pit depthBy contrasted with other pitting corrosion models,it will be reasonable to describe the maximum pit-depth curve of mild and low-alloy steel as a weibull function varying with exposure period

Abstract: The key problem of the target identification is target characteristic abstraction.In this paper,the spectrum and the frequency characteristics of the ship radiated-noise were analyzed by using LOFAR and DEMON method.The introduction of the method and some theoretical analysis are given.Emulational signal and real signal are investigated respectively and some useful results which are practical for engineering are presented.It provided effective criterion for the ship detection and identification.

Abstract: In this paper,the fuzzy-chaos algorithm is proposed,which is composed of the fuzzy genetic algorithm of bound search and the chaos algorithm.This algorithm is applied to optimize,calculate and analyze large-scale ship performance or structural characteristics.Establishing the integrate optimization mathematical model which form is the linear addition power average sum of all object functions,programming the calculation software and carrying on a lot of comparison calculation.The calculation results show that these optimization methods and the calculation software have friendly interface,good dependability and higher calculation efficiency;this optimization method and the calculation software have practicability and applied to integrally optimize the ship performance or structural characteristics is feasible.To large-scale ship project or their primary design it is worth using.

Abstract: The resistance of the high speed trimaran model with Wigley form center hull and outer hulls was tested in the Froude number between 0.1 and 0.8,and the model tests were carried out in 15 states which were configured by 3 transverse positions and by 5 longitudinal positions.The wave resistance of the high speed trimaran model is calculated by the linear wave resistance theory in comparison with the model test results.The influence of the transverse position and longitudinal position to the wave resistance coefficient is analyzed according to the model test results,where the form factor(1+K) is determined by the Prohaska method.The relationship between the form factor and the outer piece hull position is also discussed.

Abstract: The vibration and radiation induced by longitudinal vibration of shafting of underwater double cylindrical shell are calculated by FEM/BEM.A fluid-structure coupled model is built up by finite element method,and the vibration response of structure is calculated by the ANSYS.The characteristics of structural acoustic radiation are investigated by boundary element method.The location and configuration of thrust bearing are changed,resulting in modifying the amplitude and propagation path of input force,so the acoustic radiations of double cylindrical shell underwater are reduced.

Abstract: For the prediction of ship structural vibration it is of much importance to estimate exciting forces acting on ship hull from machinery in ships. Two indirect force estimation approaches are discussed in this paper. It is aimed to employ these engineering methods instead of direct force measurement in situ. For rigidly-mounted machine, least squares approach based on accelerances of the supporting structure is recommended. For resiliently-mounted machine, indirect force estimation based on impedances of the isolator is discussed. An inverse problem exists in the process of estimating forces, and singular value decomposition is employed to deal with ill-posed problem for minimizing the estimation error. There are detailed discussions in this paper about estimating accuracy and quality assessment. The inverse of condition number is recommended as a good prior criterion for choosing response positions in least squares approach. Normalized residue is recommended as another criterion to assess the quality of estimation afterwards. Experiments demonstrated that indirect approaches could be good choices for determining output forces of machinery in ships. The relative error of the results from least squares approach is 3dB. SNR (Signal to noise ratio) of the measurement plays an important role in force estimation process. Low SNR would probably he the chief cause of the error in practice. This paper can also be used to guide the characterization of vibrational source in ships.

Abstract: Based on underwater vehicle's nonlinear differential equation and observation equations,swarm intelligence algorithm is used to identify ten hydrodynamic parameters from simulation observed data of the motions of underwater vehicle.Experimental results show that this method is highly effective and efficient,and moreover it has no requirements on the differentiability and continuity of the objective function,and consequently does not need to perform complex matrix calculations,so this method is suitable for applications in identification of nonlinear hydrodynamics of complex system.

Abstract: Violent fluid motion (sloshing) occurs in such partially filled tanks when ship motion period is close to fluid natural oscillation period in these tanks. In ship design the main interest is in tank structural response and any possible damage in the form of plasticity or tearing introduced by sloshing impact pressure. In this paper, based on the approach presented by DNV (Det Norske Veritas), an improved method is presented. Three dimensional structure and fluid behavior and their interaction is analyzed by an explicit time integration method utilizing a finite element/finite volume approach and ALE coupling technique. The analysis procedure applied to an example of VLCC is outlined.

Abstract: A simplified method is developed to overcome the shortcomings in ordinary finite element methods for welding process simulation and welding residual stress prediction,such as complicated process,long running time and high cost.The method adopts the liner heat source instead of point heat source by introducing a time ratio of heating and cooling during the welding process,so that the 3-D problems are transformed into 2-D problems and save the running time a lot.The numerical results show that the present method is capable of predict welding residual stress in practical engineering and a large amount of running time and computer resources are saved under the condition of quite high accuracy.

Abstract: Aiming at the shortcoming of less precision in transforming measured acceleration signal to velocity or to elevation signal,a new method of integration transformation based on FFT time-domain transformation and EMD self-adaptive filter is presentedSimulation results of wave signal demonstrate the high precision of this method in acceleration integration transformation and the application in analyzing the angle velocity/course in some ship model's zigzag test indicates this method is effective for practical measurement

Abstract: The propulsion shaft is the most important component of power device of the ship;its stability is the basic promise of the ship's life.In this paper,the propulsion shaft of the ship is used as the subject investigated.The effect of rotation velocity on the response of the shaft under shock is considered.The coupled effect of transverse movement and rotation is investigated.The dynamics of multi-body is used to model the shaft.The equations of motion,described as nonlinear partial differential equations,of the main propulsion shaft of the ship are derived;and it is dispersed using classical theory.Finally,the Runge-Kutta method is used to do the numerical simulation.The analysis of the example shows that the effect of rotation velocity on the response of the shaft under shock can not be disregarded.

Abstract: In order to predict sonar self-noise inside the sonar dome of irregular form in the fore-body of submarines,the Integro-SEA method is established by applying the idea of integro-modal approach and the technique of virtual elastic membrane.The hydrodynamic self-noise of a rectangular sonar dome model is calculated to examine the accuracy of the Integro-SEA method.Then,the hydrodynamic self-noise of the sonar dome in the fore-body of a submarine is calculated,and the effect of trubulence boundary layer transition is also included.By the comparison of the self-noise of rectangular sonar dome,the difference between the results obtained by the classical SEA and the Integro-SEA is less than 1dB.When both of the Integro-SEA method and the modification of transition noise were considered,the difference between the calculated and the measured hydrodynamic self-noise component of a sonar dome in the fore-body of a submarine is about 2-3dB in the frequency range of 200Hz-6kHz.

Abstract: An RANS solver is used to predict roll hydrodynamic coefficients (added inertia moment and damping) of a two-dimensional section with/without bilge keels on the free surface. The viscous flow field disturbed by the forced roll motion is solved in time domain with VOF and two-phases flow approach. The roll hydrodynamic coefficients are derived from time histories of the roll hydrodynamic moments. The results are compared with published model test measurements and a fairly good agreement was found.

Abstract: A series of ITTC recommended procedures for Uncertainty Analysis in experimental fluid dynamic measurement were put into effect since 1999,but there are still a lot of details in UA application to be further discussed or revised by now. The topic in this paper is one of such details.Non-dimensional formulae are usually used to express the measured hydrodynamic forces and moments in ship model test, so that various geometric parameters are involved in uncertainty analysis.Several examples are given to illustrate some confusion in the uncertainty analysis concerning the geometric parameters and,it is recommended that it is better to perform the uncertainty analysis based more on physical and engineering consideration than on mathematical formulae.