COMPUTATION OF SHIP MANOEUVRING RELATED VISCOUS FLOW AND HYDRODYNAMIC FORCES

An efficient multi block incompressible viscous flow solver based on solving the Reynolds Averaged Navier Stokes (RANS) equations numerically has been developed that can be applied to simulation of a variety of ship maneuvering related flows and calculation of hydrodynamic forces. Valida tion and verification of the solution procedure were carried out on several model problems with good agreement to experimental and numerical results.     

MEASUREMENT OF HYDRODYNAMIC FORCES ACTING ON A CIRCULAR CYLINDER NEAR A PLANE BOUNDARY IN STEADY FLOW

In this paper,the characteristics of hydrodyna(?) forces on a circular cylindernear a plane boundary have been studied experimentally in w(?) tunnels.The drag coefficientC_D,mean lift coefficient C_(L0),T.m.s.lift coefficient C_(L Tms),maximum lift coefficient C_(L max) andfluctuating lift coefficients C'_(L Tms),C'_(L max),and lift(vortex shedding)frequency have been mea-sured on condition that the thickness of plane boundary layer,δ,was 0.1D(D is the diameter ofthe cylinder)at the station of the centre of the cylinder,and Reynolds number,Re,varied from4.5×10~3 to 1.76×10~5.The regularity of the change of these coefficients with Re and gap ratioG/D is found.The measurement of the lift frequency shows that a strong non-linear coupling ac-tion appears when the gap ratio between the circular cylinder and plane,G/D,reaches 0.5,andthe shedding of regular vortex is suppressed when G/D=0.2.     

RESEARCH ON HYDRODYNAMIC FORCES OF CAVITATING GRID FINS

Hydrodynamic forces and flow pattern of four kinds of cavitating grid fins with cavitation number from 2.5 to 0.25 were simulated numerically with a bubble two phase flow model embodied in the commercial CFD code Fluent 6. 0.Comparison with experimental datum showed that rules of hy drodynamic forces changing with cavitation number were coordinated with experiment, and cavitation made the ratio of lift to resistance decrease. Calculated axial force and chordal pressure center in all wetted condition or those at cavitation number less than 0. 75 agreed well with experiments. Normal force in all wetted condition was less by 20 per cent. The differences between computation and experiment in the total range of cavitation number were mainly because that the inciplent cavitation number in computation was less than that at experiment.     

COMPUTATION OF HYDRODYNAMIC INTERACTION FORCES BETWEEN SHIPS BASED ON B-SPLINES

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＷｉｔｈｉｎｔｈｅａｓｓｕｍｐｔｉｏｎｏｆｓｌｅｎｄｅｒ ｔｈｅｏｒｙ ,Ｙｅ ｕｎｇ[1 ,2 ] ｆｉｒｓｔｒｅｃａｓｔｔｈｅｔｈｒｅｅ ｄｉｍｅｎｓｉｏｎａｌｐｒｏｂｌｅｍｏｆｔｗｏｓｈｉｐｓｍｏｖｉｎｇｉｎａｓｈａｌｌｏｗｆｌｕｉｄｉｎｔｏｔｗｏｉｎｎｅｒｐｒｏｂｌｅｍｓａｎｄｏｎｅｏｕｔｅｒｐｒｏｂｌｅｍａｎｄｄｅｒｉｖｅｄａｐａｉｒｏｆｃｏｕｐｌｅｄｉｎｔｅｇｒａｌ ｄｉｆｆｅｒｅｎｔｉａｌｅｑｕａｔｉｏｎｓｆｏｒｄｅｔｅｒｍｉｎｉｎｇｔｈｅｕｎｋｎｏｗｎｃｒｏｓｓ ｆ…     

STUDY OF HYDRODYNAMIC FORCES OF SHIPS IN NARROW WATERWAY

1 .　INTRODUCTIONInrestricatedwaterssuchasnarrowwater ways,itisnecessarytoknowthemaneuveringcharacteristicsofships .Thecollisionofshipsisoneofthemajorreasonsofshipwreckintheworld .Thecollisionsmayoccurforavarietyofreasons .Theymaybedue ,amongotherthings ,tohumanerror ,mechanicalfailure ,weatherandwa terconditions .Butthehydrodynamicforcesbe tweentwoshipsandbetweenshipandbank ,theeffectofdepthofwateralsochangethemaneuver ingcharacteristicsofshipsgreatly .Innarrowwa terways ,specially ,the…     

ON HYDRODYNAMIC INTERACTION UPON THE WAVE FORCES ON VERTICAL PILE ARRAY

A systematic study is carried out on the hydrodynamic interaction of sin-gle-row vertical pile array with a large number of piles by using the method of wave sourcedistribution.Some new properties for the hydrodynamic interaction among piles are firstreported in this paper.The Present study shows the importance and necessity of reassess-ing the hydrodynamic interaction among multiple objects of large number to reach a com-plete understanding on that subject.     

HYDRODYNAMIC FORCE ON SMOOTH HORIZONTAL CYLINDER IN UNIFORM OSCILLATORY FLOW

ＨＹＤＲＯＤＹＮＡＭＩＣ　ＦＯＲＣＥ　ＯＮ　ＳＭＯＯＴＨ　ＨＯＲＩＺＯＮＴＡＬ　ＣＹＬＩＮＤＥＲ　ＩＮ　ＵＮＩＦＯＲＭ　ＯＳＣＩＬＬＡＴＯＲＹ　ＦＬＯＷＨＹＤＲＯＤＹＮＡＭＩＣＦＯＲＣＥＯＮＳＭＯＯＴＨＨＯＲＩＺＯＮＴＡＬＣＹＬＩＮＤＥＲＩＮＵＮＩＦ...     

INFLUENCING FACTORS FOR THE ENERGY DISSIPATION RATIO OF STEPPED SPILLWAYS

In order to search for the measure to increase the energy dissipation ratio of stepped spillways, some main influencing factors for the energy dissipation ratio of stepped spillways, such as unit discharge, dam slope, height of step and so on, were studied. The results show that the energy dissipation ratio decreases with the increase in the unit discharge and increases as the slope becomes gentle. The effects of step height on the energy dissipation ratio are closely related to unit discharge. If the unit discharge is smaller, the change of energy dissipation ratio with step height becomes greater. While, if the unit discharge is greater, the influence of step height on energy dissipation ratio is very little. According to the distributions of the turbulence kinetic energy and turbulence dissipation rate obtained by numerical simulation, the basic reason of the decrease of energy dissipation ratio with the increase in the unit discharge was discussed and some specific measures to increase the energy dissipation ratio were suggested.     

THE APPLICATIONS AND STUDY OF NUMERICAL SIMULATION OF TURBULENCE FLOW WITH FREE SURFACE IN HYDRAULIC SPILL WAYS STRUCTURE

The turbulence flow Free Surface has important applications in hydraulic spillways structure,such as the hydraulic jump,energy dissipation flow etc.This is being considered as very complicated flow,and has not yet been solved quite well by numerical method. In this paper,a Large-scale computational software package are developed for numerical laboratory of hydraulic spillway structure.Some methods,such as turbulence model, free surface and irregular boundary treating techniques,scientific computer visualization are put forward and performed.     

HYDRODYNAMIC MODEL OF THE WEIS-FOGH HYDROFOIL

ＨＹＤＲＯＤＹＮＡＭＩＣＭＯＤＥＬＯＦＴＨＥＷＥＩＳ－ＦＯＧＨＨＹＤＲＯＦＯＩＬＺｈａｎｇＳｈｅ－ｓｈｅｎｇ；ＷｕＸｉｕ－ｈｅｎｇ；ＷａｎｇＸｉａｎ－ｆｕ（Ｄｅｐａｒｔｍｅｎｔｏｆｍａｔｈｅｍａｔｉｃｓ，ＷｕｈａｎＴｒａｎｓｐｏｒｔａｔｉｏｎＵｎｉｖ...     

HYDRODYNAMIC OPTIMIZATION DESIGN OF LOW SOLIDITY VANED DIFFUSER FOR A CENTRIFUGAL PUMP USING GENETIC ALGORITHMS

1 .　INTRODUCTIONVaneddiffusershavebeenwidelyappliedtocentrifugalpumpsinmodernindustry .Thevaneddiffusercanefficientlyconvertthekineticenergyattheimpellerexitintothestaticpressureriseincomparisonwiththevanelessdiffuserforthecen trifugalpump .Thegooddesignofvaneddiffuserscannotonlyleadtocompactsize ,butalsocanim provethehydrodynamicperformanceofcentrifu galpumps[1] .Inrecentyears ,manyresearchershave paidmuchattentiontotheapplicationofLowSolidityvanedDiffuser (LSD )incentrifugalcompresso…     

EFFECTS OF WATER-DEPTH ON HYDRODYNAMIC FORCE OF ARTIFICIAL REEF

The effects of water-depth on the hydrodynamic force of the artificial reef were studied by simulating regular and irregular waves. The computational results show that the water-depth has a substantial effect on hydrodynamic force. The hydrodynamic force increases with the decrease of water-depth in shallow. Especially, in the ultra-shallow water these loads increase very evidently with the decrease of water-depth. The long-term values of hydrodynamic force increase with the decrease of the ratio of water-depth to reef height, and are about 10% larger than those of deep water when the ratio of water-depth to reef height is 4.0. However water-depth hardly affects the long term values of hydrodynamic force when the ratio of water-depth to reef height is larger than 6.0.     

CALCULATION OF MANOEUVERING HYDRODYNAMIC FORCE INCLUDING THE EFFECT OF VISCOSITY

Based on the method of Chapman and Yamasaki, this paper calculates the wave making hydrodynamic forces acting on a yawed ship. In order to study the effect of viscosity, this paper calculates the wave making resistance of a new ship model whose boundary is formed by adding the displacement thickness on real ship body. The comparisons between the calculated results of a Wigley model and experimental values verify the validity of the new model and the numerical methods.     

CALCULATION OF VISCOUS HYDRODYNAMIC FORCES ON A SHIP HULL IN OBLIQUE MOTION

This paper focuses on computations of viscous hydrodynamic forces acting on a ship in oblique motion by solving the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations. The standard κ-ε turbulence model with wall function was applied. The conservation equations were discretized by a cell-centered second-order Finite Volume Method (FVM) in a block-structured body-fitted grid and the coupling of velocity and pressure was resolved with the SIMPLE method. Computations were performed for a Wigley hull model to investigate the viscous flows around it. The results show good agreement with experimental data and more reasonable prediction of hydrodynamic forces and moments than other numerical results available.     

THE IRREGULAR BREAKING WAVE FORCES ON VERTICAL WALL

A method for the calculation of total horizontal wave forces by irregular breaking waves on vertical wall was developed by authors, which was based on physical model test, dimensionless analysis and assessment of real construction. The methods for the determination of pressure distribution of horizontal forces on vertical wall as well as u-plift forces on the bottom of wall are also given. The comparison between calculated results by this method and samples of real construction are very well.     

PREDICTION OF LOADING DISTRIBUTION AND HYDRODYNAMIC MEASUREMENTS FOR PROPELLER BLADES IN A RIM DRIVEN THRU-STER

This article presents an approach which employs a commercial Reynolds-Averaged Navier-Stokes(RANS)solver to predict the steady wake field and loading distributions for a rim driven thruster.Four different cases of propeller blades are chosen to be calculated with the presented method.The propeller blade radial circulation and chordwise circulation density distributions are analyzed.The maximum radial circulation is found at the blade tip,which is different from conventional shaft driven propeller.The numerical results indicate that there is no tip leakage vortex in rim driven propulors.But there exist the tip joint vortex and the root region vortex.Bollard characteristics are calculated by taking rim surface effect into account.From the predicted results the second case in this paper is selected as the final one to perform hydrodynamic experiment.The calculation results with empirical rim surface corrections are compared with the measurement.It shows that the developed numerical method can well predict hydrodynamic performances of the rim driven thruster.     

BREAKING WAVE FORCES ON VERTICAL CYLINDERS

The breaking wave forces on vertical cylinders in shallow waters were studied by means of experimental methods. The results indicate that the breaking wave pressure is distributed exponentially with respect to water depth. An experimental formula was given using the test data. Compared with test data, the calculated breaking wave forces are in good agreement with the test data.     

NUMERICAL SIMULATION OF THE HYDRODYNAMIC PERFORMANCE OF AN UNSYMMETRICAL FLAPPING CAUDAL FIN

A comprehensive numerical simulation of the hydrodynamic performance of a caudal fin with unsymmetric flapping motion is carried out. The unsymmetrical motion is induced by adding a pitch bias or a heave bias. A numerical simulation program based on the unsteady panel method is developed to simulate the hydrodynamics of an unsymmetrical flapping caudal fin. A CFD code based on Navier-Stokes equations is used to analyze the flow field. Computational results of both the panel method and the CFD method indicate that the hydrodynamics are greatly affected by the pitch bias and the heave bias. The mean lateral force coefficient is not zero as in contrast with the symmetrical flapping motion. By increasing the pitch bias angle, the mean thrust force coefficient is reduced rapidly. By adding a heave bias, the hydrodynamic coefficients are separated as two parts: in one part, the amplitude is the heave amplitude plus the bias and in the other part, it is the heave amplitude minus the bias. Analysis of the flow field shows that the vortex distribution is not symmetrical, which generates the non-zero mean lateral force coefficient.     

RESEARCH ON THE HYDRODYNAMIC STABILITY OF FIBRE SUSPENSIONS

BRIEFINTRODUCTIONOFTHEPAPER :　Fibresuspensionshavebeenveryfamiliarinnatureandinmanyfieldsofindustry .Researchesofthemin volvemanybranchesofsubjectsandhavegreata cademicvalues .Thisthesisstudiesthestabilityoffibresuspensionswiththeoretical,numericalandexperimentalmethods .Firstthelinearstabilityanalysisisperformedforfibresuspensionsutilizingtheflowstability ,slender bodyandorientationtensortheories .Thegoverningequationsofchanneland pipesuspen sionsofdifferentstabilityhandlingmodesa…     

A 2D/3D COUPLED MODEL FOR WAVE FORCES ON MOORED SHIPS IN A HARBOR

1 .　INTRODUCTIONAccordingtoRef .[1],themotionofashipmooredagainstquayinaharborcanbestudiedintwosteps :harborwaveconditionsandwaveexcit ingforcesactingonthemooredshipshouldbegotfirst,andthendynamicresponsesofthemooringsystemincludingtheshipunderwaveexcitingforcescanbestudiedseparately .Asthefirststep ,ahybridmodelbasedonthecombinationoftheBoussinesq typeshallow waterwavemodelandthe3Dviscousflowmodelisproposedinthispaperforthetime domaincalculationofwaveexcitingforcesonmooredshipsinaharbor…