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Modelling of multi-bodies in close proximity under water waves——Fluid resonance in narrow gaps

Science china(Physics,Mechanics & Astronomy) 2011年第1期54卷 16-25页

作者： LU Lin1,2,TENG Bin3,CHENG Liang 4,SUN Liang5 & CHEN XiaoBo6 1 Center for Deepwater engineering,dalian university of technology,dalian 116024,china 2 state key laboratory of Structural Analysis for Industrial Equipment,dalian university of technology,dalian 116024,china 3 state key laboratory of coastal and offshore engineering,dalian university of technology,dalian 116024,china 4 School of Civil and Resource engineering,The university of Western Australia,Crawly 6003,Australia 5 Centre for offshore Research and engineering,Department of Civil engineering,National university of Singapore,117576,Singapore 6 Research Department,Bureau Veritas,Neuilly-Sur-Seine,92570,France Center for Deepwater engineering Dalian University of Technology Dalian China state key laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian China state key laboratory of coastal and offshore engineering Dalian University of Technology Dalian China School of Civil and Resource engineering The University of Western Australia Crawly Australia Centre for offshore Research and engineering Department of Civil Engineering National University of Singapore Singapore Singapore Research Department Bureau Veritas Neuilly-Sur-Seine France

Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μ the damping coefficient and V the local averaging flow velocity) are employed in this work to investigate the phenomenon of fluid resonance in narrow gaps between multi-bodies in close proximity under water *** numerical results are compared with experimental data available in the *** comparison demonstrates that both the viscous fluid model and the potential flow model are able to predict the resonant frequency reasonably *** the conventional potential flow model(without artificial damping term) significantly over-predicts the wave height in narrow gaps around the resonant *** order to calibrate the appropriate damping coefficient used for the potential model and make it work as well as the viscous fluid model in predicting the resonant wave height in narrow gaps but with little computational efforts,the dependence of damping coefficient μ on the body geometric dimensions is examined considering the parameters of gap width Bg,body draft D,body breadth ratio Br and body number n(n = 2,3),where Br = BB/BA for the case of two bodies(Body A and Body B) with different breadths of BA and BB,*** was confirmed that the damping coefficient used for the potential flow model is not sensitive to the geometric dimensions and spatial *** was found that μ∈ [0.4,0.5] may guarantee the variation of Hg/H0 with kh to be generally in good agreement with the experimental data and the results of viscous fluid model,where Hg is the excited wave height in narrow gaps under various dimensionless incident wave frequencies kh,H0 is the incident wave height,k = 2π/L is the wave number and h is the water depth.

关键词： narrow gap fluid resonance water wave viscous fluid model potential flow model finite element method boundary element method

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Reflection of regular and irregular waves from a partially perforated caisson breakwater with a rock-filled core

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Acta Oceanologica Sinica 2007年第3期26卷 129-141页

作者： LIU Yong1, LI Yucheng 1, 2, TENG Bin1, MA Baolian3 1.state key laboratory of coastal and offshore engineering, dalian university of technology, dalian 116024, china 2.R&D Center for Civil engineering technology, dalian university, dalian 116622, china 3.Tianjin Maritime Safety Administration, Tianjin 300456, china dalian university of technology State Key Laboratory of Coastal and Offshore Engineering Dalian 116024 Tianjin Maritime Safety Administration Tianjin 300456

The reflection of regular and irregular waves from a partially perforated caisson breakwater with a rock-filled core is examined. The present mathematical model is developed by means of the matched eigenfunction method. Numerical results of the present model are compared with the experimental data of different researchers. Numerical examples are given to examine the effect of rock fill on the reflection coefficient. The differences between regular and irregular waves are also investigated by means of theoretical and experimental results. It is found that the minimum reflection coefficient of irregular waves is larger than that of corresponding regular waves, but the contrary is the case for the maximum reflection coefficient.

关键词： reflection coefficient regular waves irregular waves partially perforated caisson rock fill

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A modified method for simulating non-stationary multi-point earthquake ground motion

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Earthquake engineering and engineering Vibration 2010年第2期9卷 201-211页

作者： Li Minggao,Li Xin and Zhou Jing state key laboratory of coastal and offshore engineering,dalian university of technology,dalian 116024,china state key laboratory of coastal and offshore engineering Dalian University of Technology Dalian China

A spectral-representation-based algorithm is proposed to simulate non-stationary and stochastic processes with evolutionary power,according to a prescribed non-stationary cross-spectral density matrix. Non-stationary multi-point seismic ground motions at different locations on the ground surface are generated for use in engineering applications. First,a modified iterative procedure is used to generate uniformly modulated non-stationary ground motion time histories which are compatible with the prescribed power spectrum. Then,ground motion time histories are modeled as a non-stationary stochastic process with amplitude and frequency modulation. The characteristic frequency and damping ratio of the Clough-Penzien acceleration spectrum are considered as a function of time in order to study the frequency time variation. Finally,two numerical examples are presented to validate the efficiency of the proposed method,and the results show that this method can be effectively applied to the dynamic seismic analysis of long and large scale structures.

关键词： multi-support excitation spatial correlation power spectrum-compatibility non-stationary ground motion simulation

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WAVE-CURRENT INTERACTIONS WITH THREE-DIMENSIONAL FLOATING BODIES

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Journal of Hydrodynamics 2010年第2期22卷 229-240页

作者： LIU Zhen TENG Bin NING De-zhi GOU Ying state key laboratory of coastal and offshore engineering Dalian University of Technology Dalian 116024China state key laboratory of Satellite Ocean Environment Dyamics Hangzhou 310012 China

A Time-domain Higher-Order Boundary Element Method（THOBEM） is developed for simulating wave-current interactions with 3-D floating *** a Taylor series expansion and a perturbation procedure,the model is formulated to the first-order in the wave steepness and in the current velocity,*** boundary value problem is decomposed into a steady double-body flow problem and an unsteady wave ***-order boundary integral equation methods are then used to solve the proposed problems with a fourth-order Runge-Kutta method for the time *** artificial damping layer is adopted to dissipate the scattering *** from the other time-domain numerical models,which are often focused on the wave-current interaction with restrained bodies,the present model deals with a floating *** numerical results of wave forces,wave run-up and body response are all in a close agreement with those obtained by frequency-domain *** proposed numerical model is further applied to investigate wave-current interactions with a floating body of complicated *** this work,the regular and focused wave combined with current interacting with a truss-spar platform is investigated.

关键词： wave-current interaction floating bodies time-domain simulation Time-domain Higher-Order Boundary Element Method(THOBEM)

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NUMERICAL SIMULATON OF IMPROVED BOUSSINESQ EQUATIONS BY A FINITE ELEMENT METHOD

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Journal of Hydrodynamics 2003年第4期15卷 31-40页

作者： Zhao Ming, Teng Bin, Liu Shu-xue state key laboratory of coastal and offshore engineering, dalian university of technology, dalian 116024, china Lab. of coastal and offshore Eng. Dalian Univ. of Technol. Dalian 116024 China

The improved Boussinesq equations for varying depth derived by Beji andNadaoka significantly improved the linear dispersive properties of wave models in intermediate waterdepths. In this study, a finite element method was developed to solve the improved Boussinesqequations. A spongy layer was applied at the open boundary of the computational domain to absorb thewave energy. The fourth-order predictor-corrector method was employed in the time *** test cases were illustrated. The numerical results of this model were compared withlaboratory data and those from other numerical models. It turns out that the present numerical modelis capable of giving satisactory prediction for wave propagation.

关键词： boussinesq equations finite element method numerical simulation

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Normalization of Hydrodynamic Coefficients in Morison Equation

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china Ocean engineering 1999年第2期14卷 125-132页

作者： LI Yucheng Professor, the state key laboratory of coastal and offshore engineering, dalian university of technology, dalian 116024, P. R. china. state key laboratory of coastal and offshore engineering Dalian University of Technology Dalian 116024 China

The hydrodynamic coefficients C-d and C-m are not only dependent on the size of slender cylinder, its location in water, KC number and Re number, but also vary with environmental conditions, i.e., in regular waves or in irregular waves, in pure waves or in wave-current coexisting field. In this paper, the normalization of hydrodynamic coefficients for various environmental conditions is discussed. When a proper definition of KC number and proper characteristic values of irregular waves are used, a unified relationship between C-d, C-m and KC number for regular waves, irregular waves, pure waves and wave-current coexisting field can be obtained.

关键词： Morison Equation drag force coefficient inertia force coefficient hydrodynamic coefficient normalization

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Mechanics Behavior of Ultra High Toughness Cementitious Composites after Freezing and Thawing

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Journal of Wuhan university of technology(Materials Science) 2010年第3期25卷 509-514页

作者：徐世烺 The state key laboratory of coastal and offshore engineering Dalian University of Technology

Mechanical behaviors of UHTCC after freezing and thawing were investigated,and compared with those of steel fiber reinforced concrete（SFRC）,air-entrained concrete（AEC） and ordinary concrete（OC）.Four point bending tests had been applied after different freezing-thawing cycles（0,50,100,150,200 and 300 cycles,respectively）.The results showed that residual flexural strength of UHTCC after 300 freezing-thawing cycles was 10.62 MPa（70% of no freezing thawing ones）,while 1.58 MPa（17% of no freezing thawing ones） for *** toughness of UHTCC decreased by 17%,while 70% for SFRC *** has been demonstrated experimentally that UHTCC without any air-entraining agent could resist freezing-thawing and retain its high toughness characteristic in cold ***,UHTCC could be put into practice for new-built or retrofit of infrastructures in cold regions.

关键词： ultra high toughness cementitious composites cyclic freezing and thawing flexural strength multiple cracking flexural toughness

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Numerical Wave Channel with Absorbing Wave-Maker

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china Ocean engineering 1995年第2期10卷 149-160页

作者： Wang YongxueProfessor, state key laboratory of coastal and offshore engineering, dalian university of technology, dalian 116024

The numerical wave channel has been developed based on the volume of fluid method (VOF) in conjunction with the Navier-Stokes equations. The absorbing wave-maker boundary on the left side of the channel is presented by prescribing velocity reference to linear wave-maker theory. The principle of which is that the numerical wave-maker is designed to move in a way that generates the required incident wave and cancels out any reflected wave that reach it at the same time. On the right side of the channel, the open boundary is set to permit incident waves to be transmitted freely. The parametric studies have been carried out at a range of ratios of water depth to wave length d/ L from 0.124 to 0.219, with wave height in the front of paddle/water depth ratio (H0 / d) from 0.1 to 0.3. Wave height, wave pressure distribution along the channel and velocity field are obtained for both open boundary condition and reflective boundary condition at the other end of the channel. For a reflective case, it is shown that the absorbing wave-maker is very effective in canceling out the reflected wave that reaches the numerical paddle and highly repeatable waves can be generated.

关键词： numerical wave channel absorbing wave-maker VOF method

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NUMERICAL MODELLING OF FREE-SURFACE FLOWS WITH BOTTOM AND SURFACE-LAYER PRESSURE TREATMENT

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Journal of Hydrodynamics 2009年第3期21卷 352-359页

作者： WANG Kun state key laboratory of coastal and offshore engineering Dalian University of Technology Dalian 116024 China

A new non-hydrostatic numerical model with the three-dimensional Navier-Stokes equations on structured grids was constructed and discussed. The algorithm is based upon a staggered finite difference Crank-Nicholson scheme on a Cartesian grid. The eddy viscosity coefficient was calculated by the efficient k-ε turbulence model. A new surface-layer non-hydrostatic treatment and a local cell bottom treatment were introduced so that the three-dimensional model is fully non-hydrostatic and is free of any hydrostatic assumption. The developed model is second-order accuracy in both time and space when semi-implicit coefficient is set to 0.5. The validity of the present solution algorithm was demonstrated from its application to the three-dimension channel flow and the wave propagation over a submerged bar problems.

关键词： Navier-Stokes equations implicit k -ε turbulence model surface-layer non-hydrostatic treatment local cell bottom treatment

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ANALYTICAL STUDY OF WAVE MAKING IN A FLUME WITH A PARTIALLY REFLECTING END-WALL

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Journal of Hydrodynamics 2010年第3期22卷 402-409页

作者： ZHOU Bin-zhen NING De-zhi TENG Bin CHEN Li-fen state key laboratory of coastal and offshore engineering Dalian University of Technology Dalian 116024China state key laboratory of Hydrology-Water Resources and Hydraulic engineering Nanjing Hydraulic ResearchInstitute Nanjing 210029 China

Based on the eigenfunction expansion technique, the wave generation by a piston wave maker in a wave flume with a partially reflecting end-wall is studied. The corresponding velocity potential and wave elevation in the flume are obtained. The present analytical solution is verified by the numerical results obtained from a time-domain higher-order boundary element method in a closed flume. Numerical experiments are further carried out to study the difference between the partial/full reflection boundary and the transmission boundary and the effects of the reflection coefficient and the motion period of the wave maker on the wave height. Meanwhile, the natural frequency of the wave flume can be obtained from the analytical expression. The resonance occurs when the motion frequency is equal to the natural frequency. Even the partial reflection of the end-wall in the wave flume experiments has a great influence on the wave height, therefore, inaccurate measurements would be resulted in long-time simulations, especially when the wave frequency approaches the wave flume natural frequency. The present study can serve as a guidance for the physical experiment in wave flumes.

关键词： wave flume wave maker partially reflecting end-wall resonance eigenfunction analytical study

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