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hydrodynamic forces FOR OVERTOPPING SPILLWAYS

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Journal of hydrodynamics 1993年第2期5卷 19-29页

作者： Ashok K.Chugh U.S.Department of the Interior,Bureau of Reclamation Eugineering and Research,Deuver,Colorado 80225 U.S. Dep of the Interior Denver United States

Expressions are derived for calculating hydrodynamic forces from the unit dis- charge,channel slope,and flow and velocity profiles on an overflow spillway.A sample prob- lem is included to illustrate the use of the id... 详细信息

关键词： hydrodynamic forces spillways embankment dam

CALCULATION OF VISCOUS hydrodynamic forces ON A SHIP HULL IN OBLIQUE MOTION

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Journal of hydrodynamics 2004年第1期16卷 84-89页

作者： QIULei ZOUZao-jian ZHANGXie-dong SchoolofTransportation WuhanUniversityofTechnologyWuhan430063China SchoolofNavalArchitectureandOceanEngineering.ShanghaiJiaotongUniversity Shanghai200030China SchoolofTransportation WuhanUniversityofTechnology.Wuhan430063China

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

关键词： viscous flow hydrodynamic forces multi-block finite-volume method

Influence of temperature and salinity on hydrodynamic forces

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Journal of Ocean Engineering and Science 2016年第4期1卷 325-336页

作者： A.Escobar V.Negro J.S.López-Gutiérrez M.D.Esteban Technical University of Madrid C/Profesor Aranguren S/N28040 MadridSpain

The purpose of this study is to introduce an innovative approach to offshore engineering so as to take variations in sea temperature and salinity into account in the calculation of hydrodynamic forces.With this in mind,a thorough critical analysis of the influence of sea temperature and salinity on hydrodynamic forces on piles like those used nowadays in offshore wind farms will be carried out.This influence on hydrodynamic forces occurs through a change in water density and viscosity due to temperature and salinity variation.Therefore,the aim here is to observe whether models currently used to estimate wave forces on piles are valid for different ranges of sea temperature and salinity apart from observing the limit when diffraction or nonlinear effects arise combining both effects with the magnitude of the pile diameter.Hence,specific software has been developed to simulate equations in fluid mechanics taking into account nonlinear and diffraction effects.This software enables wave produced forces on a cylinder supported on the sea bed to be calculated.The study includes observations on the calculation model’s sensitivity as to a variation in the cylinder’s diameter,on the one hand and,on the other,as to temperature and salinity variation.This software will enable an iterative calculation to be made for finding out the shape the pressure wave caused when a wave passes over will have for different pile diameters and water with different temperature and salinity.

关键词： Sea temperature Salinity hydrodynamic forces Wave action Offshore wind farms

hydrodynamic forces on Smooth Inclined Cyh'nders in Oscillatory Flow

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China Ocean Engineering 1994年第3期9卷 293-306页

作者： Kang Haigui Department of Civil Engineering Dalian University of TechnologyDalian 116023

-The hydrodynamic forces on a smooth inclined circular cylinder exposed to oscillating flow were experimentally investigated at Reynolds number (Re) in the range 40000-200000 and Keulegan-Capenter number (KC) in the interval from 5-40. In the test, Re number and KC number were varied systematically. The inertia force coefficient (Cu) and the drag force coefficient (CD) in Morison equation were determined from the measured loads and the water particle kinematics. In this analysis a modified form of Morison equation was used since it uses the normal velocity and acceleration. Thus, the applicability of the Cross Flow Principle was assumed. This principle, simply stated, is as follows: the force acting in the direction normal to the axis of a cylinder placed at some oblique angle with the direction of flow is expressed in terms of the normal component of flow only, and the axial component is disregarded. Both the total in-line force coefficient (CF) and transverse force (lift) coefficient (Cf) were analyzed in terms of their maximum and root mean square values. All the in-line and lift force coefficients were given as a functions of Re and KC number. F'rom this research, it can be seen that the Cross-Flow Principle does not always work well. It seems valid for the total in- line force at high Re and large KC numbers. The Cu for a = 45 is larger and the CD for a = 45 is smaller than that for a = 90 ?and Re> 80000. The hydrodynamic force coefficients CD and Cu for the inclined cylinder are only the functions of the oblique angle (a) and KC number, but not of the Re number.

关键词： wave forces hydrodynamic forces inclined cylinder oscillatory flow

COMPUTATION OF SHIP MANOEUVRING RELATED VISCOUS FLOW AND hydrodynamic forces

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Journal of hydrodynamics 2005年第1期17卷 125-125页

作者： QIULei ZouZao-jian LiuYing-zhong XuHan-zhcn ZhengXue-ling ZhangWei-kang WuXiu-heng ZhangLe-wen LiuZu-yuan WuhanUniversityofTechnology（WUT） Wuhan430063 China ShanghaiJiaotongUniversity ShanghaiJiaotongUniversity.Chairman HuazhongUniversityofSci-enceandTechnology NavyUniversityofEngi-neering WuhanUniversityofTechnology（WUT）

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. Validation and verification of the solution procedure were carried out on several model problems with good agreement to experimental and numerical results.

关键词： ship maneuvering viscous flow hydrodynamic forces CFD numerical simulation visualization

hydrodynamic FORCE ON SMOOTH HORIZONTAL CYLINDER IN UNIFORM OSCILLATORY FLOW

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Journal of hydrodynamics 1994年第2期6卷 8-22页

作者： Kang Hai-gui(Dalian University of Technology,Dalian 116024, P. R. China )

The hydrodynamic forces on a smooth horizontal circular cylinder exposed to oscillating flow have been experimentally investigated at Reynolds numbers (Re) in the range 20, 000 - 260, 000 (subcritical and transcritical regimes) and Keulegan- Carpenter numbers (Kc) in the interval from 5 to 40. In the tests, the Re number and Kc number were varied inertia systematically. The drag force coefficnent CD and inertia force coefficient CM in Morison equation have been determined through the use of Least Square Method. Both total in-line force coefficient CF and transverse force (lift) coefficient CL have been analysed in terms of their maximum and root mean square values. All the in-line and lift force coefficinets were given as a function of Re and Kc number, and also their deviations with the average value have been shown. The principal results are as follows: for the Re ≥80, 000, all the hydrodynamic force coefficients, including CD, CM, CP and CL,are at best very weak functions of Reynolds number, and each of them tends towards a certain constant with increasing Kc number; for the Re< 80, 000, the drag force coefficient CD decreases with increasing Re number, and inertia force coefficient CM increases with increasing Re number.The tendencies of drag and inertia coefficients versus Kc number for the Re ≥10￣5 are very similar to the others, which are very close to the Rodenbusch and Cutierrez's (1983) but are somewhat larger than the Sarpkaya's (1976 and 1986) and Bearman et al.' s(1985).

关键词： wave forces hydrodynamic forces horizontal cylinder oscillatory flow

Transient curvilinear-coordinate based fully nonlinear model for wave propagation and interactions with curved boundaries

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Journal of hydrodynamics 2018年第4期30卷 549-563页

作者： Yu-Hsiang Chen Keh-Han Wang Department of Civil and Environmental Engineering University of Houston

This paper presents a newly developed 3-D fully nonlinear wave model in a transient curvilinear coordinate system to simulate propagation of nonlinear waves and their interactions with curved boundaries and cylindrical structures. A mixed explicit and implicit finite difference scheme was utilized to solve the transformed governing equation and boundary conditions in grid systems fitting closely to the irregular boundaries and the time varying free surface. The model＇s performance was firstly tested by simulating a solitary wave propagating in a curved channel. This three-dimensional solver, after comparing the results with those obtained from the generalized Boussinesq（g B） model, is demonstrated to be able to produce stable and reliable predictions on the variations of nonlinear waves propagating in a channel with irregular boundary. The results for modeling a solitary wave encountering a vertical cylinder are also presented. It is found the computed wave elevations and hydrodynamic forces agree reasonably well with the experimental measurements and other numerical results.

关键词： Solitary wave curvilinear coordinate transformation curved channel wave scattering hydrodynamic forces

Numerical investigation on fluid forces of piggyback circular cylinders in tandem arrangement at low Reynolds numbers

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Acta Mechanica Sinica 2021年第4期37卷 599-612,I0002页

作者： Linfeng Chen Yuhong Dong School of Naval Architecture and Ocean Engineering Jiangsu University of Science and TechnologyJiangsu 212003China Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering Scienceand Shanghai Key Laboratory of Mechanics in Energy EngineeringShanghai UniversityShanghai 200072China

Numerical simulations of flows past the piggyback circular cylinders in tandem arrangement are performed by solving the variational multiscale formulation of the incompressible Navier-Stokes equations using in-house finite element method(FEM)codes.The effects of the gap-spacing-to-diameter(G/D)and the two diameter ratio(d/D)on the flow characteristics and the reductions of the root-mean-square(RMS)drag and lift coefficients are considered for Reynolds numbers(Res)are 100 and 200.The validation shows the fluid force coefficients obtained by the in-house FEM codes are in good agreement with the results in the existing literatures.The obtained results show that,with a proper placement of the smaller cylinder(d/D=0.2)behind the larger cylinder,the RMS drag and lift coefficients largely decrease compared to those of the single circular cylinder.When d/D=0.2,the largest reductions of the RMS lift coefficient of the larger cylinder and the RMS total lift coefficient appear at G/D=1.2 as Re=100 and at G/D=1.0 as Re=200.It is observed that the proper placement of the smaller cylinder causes the surrounding vorticity to take opposite sign with the vorticity in the outer region so as to suppress and postpone the vortex shedding in the wake,and that the different positions of the vortex shedding at two Res cause that the largest reductions of the RMS lift coefficient of the larger cylinder and the RMS total lift coefficient appear at different G/D as Re is different.When d/D varies,the variation of the RMS total lift coefficient behaves differently at two Res.It decreases with J/D increasing at Re=100,while it no longer monotonously varies with J/D,but reaches a minimum in the considered range of d/D at Re=200.Moreover,the larger d/D results in stronger suppression and postponement of the vortex shedding in the wake.

关键词： Piggyback circular cylinders hydrodynamic forces Vortex shedding Finite element method Variational multiscale method

THE RADIATION AND DIFFRACTION OF WATER WAVES BY A BOTTOM-MOUNTED CIRCULAR CYLINDER IN A TWO-LAYER FLUID

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Journal of hydrodynamics 2007年第1期19卷 1-8页

作者： YOU Yun-xiang SHI Qiang MIAO Guo-ping School of Naval Architecture Ocean and Civil Engineering Shanghai Jiaotong University Shanghai 200030 China.

An analytical method was proposed to analyze the radiation and diffraction of water waves by a bottom-mounted circular cylinder in a two-layer fluid. Analytical expressions for added mass and damping coefficients, as well as the wave excitation forces of the circular cylinder were obtained by an eigenfunction expansion method. The hydrodynamic forces on the bottom-mounted circular cylinder in a two-layer fluid include not only the added mass and damping coefficients, but also the wave forces of the surface and internal-wave modes. This is different from the case of a homogenous fluid. Some examples were given, showing that density stratification can have a relative large effect on these hydrodynamic forces over a wide range of frequencies.

关键词： two-layer fluid bottom-mounted cylinder,surface-wave mode internal-wave mode hydrodynamic forces