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Study on Energy Spectrum Instability in the Processes of Propagating and Breaking of Focusing Waves

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China Ocean Engineering 2019年第1期33卷 86-93页

作者： ZHANG Yi-hui liang shu-xiu SUN Zhao-chen State Key Laboratory of Lake Science and Environment Nanjing Institute of Geography and LimnologyChinese Academy of Sciences State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology

Based on phase focusing theory, focusing waves with different spectral types and breaking severities were generated in a wave flume. The time series of surface elevation fluctuation along the flume were obtained by utilizing 22 wave probes mounted along the mid-stream of the flume. Based on the wave spectrum obtained using fast Fourier transform(FFT), the instability characteristics of the energy spectrum were reported in this paper. By analyzing the variation of total spectral energy, the total spectral energy after wave breaking was found to clearly decrease, and the loss value and ratio gradually increased and tended to stabilize with the enhancement of breaking severity for different spectral types. When wave breaking occurred, the energy loss was primarily in a high-frequency range of f/fp>1.0, and energy gain was primarily in a low-frequency range of f/fp<1.0. As the breaking severity increased, the energy gain-loss ratio decreased gradually, which demonstrates that the energy was mostly dissipated. For plunging waves, the energy gain-loss ratio reached 24% for the constant wave steepness(CWS) spectrum, and was slightly larger at approximately 30% for the constant wave amplitude(CWA) spectrum, and was the largest at approximately 42% for the Pierson-Moskowitz(PM) spectrum.

关键词： phase focusing wave breaking wave surface wave steepness

Hydroelastic Response of VLFS with An Attached Submerged Horizontal Solid/Porous Plate Under Wave Action

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China Ocean Engineering 2020年第4期34卷 451-462页

作者： FENG Ming-wei SUN Zhao-chen liang shu-xiu LIU Bi-jin State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China School of Civil Engineering and Architecture Xiamen University of TechnologyXiamen 361024China

The hydroelastic responses of a submerged horizontal solid/porous plate attached at the front of a very large rectangular floating structure(VLFS)under wave action has been investigated in the context of linear water wave ***’s law is adopted to represent energy dissipation in *** is assumed that the porous plates are made of material with very fine pores so that the normal velocity across the perforated porous is linearly associated with the pressure *** the analytic method,the eigenfunction expansion-matching method(EEMM)for multiple domains is applied to solve the hydrodynamic problem and the elastic equation of motion is solved by the modal expansion *** performance of the proposed submerged horizontal solid/porous plate can be significantly enhanced by selecting optimal design parameters,such as plate length,horizontal position,submerged depth and *** is concluded that good damping effect can be achieved through installation of solid and porous *** plate has better damping effect at low frequencies,while solid plate has better damping effect at high *** optimal ratio of plate length to water depth is 0.25-0.375,and the optimal ratio of submerged depth to water depth is 0.09-0.181.

关键词： VLFS hydroelastic response Darcy’s law eigenfunction expansion-matching method submerged horizontal solid/porous plate

A Comprehensive Lagrangian Transport Study in A Long-Narrow Bay,Xiangshan Bay,China

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China Ocean Engineering 2020年第4期34卷 581-588页

作者： HAN Song-lin liang shu-xiu WANG Xing-gang SUN Zhao-chen Hydraulics Department Changjiang River Scientific Research InstituteWuhan 430010China State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China Nanjing Hydraulic Research Institute Nanjing 210029China

Study on the transport and mixing in coastal waters is of great concern to the ocean resources exploitation and ecological system *** methods are direct and effective of researching mass *** Lagrangian tools were adopted and combined to describe water transport in a long-narrow bay,Xiangshan Bay,*** on the fields of tidal velocity simulated from the 3-D hydrodynamic model,Lagrangian Coherent Structures(LCSs)and synoptic Lagrangian maps(SLMs)were calculated in the study *** comparison of the results,the features and relation of the two tools were *** results show that the LCSs act as the separatrix of the water regions with different transport characteristics and can identify the water areas with different transport time *** comprehensive application of the Lagrangian tools is helpful to obtain more insight into the water transport process.

关键词： transport and mixing Lagrangian coherent structures synoptic Lagrangian maps Xiangshan Bay

SPH Numerical Modeling for the Wave–Thin Structure Interaction

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China Ocean Engineering 2018年第2期32卷 157-168页

作者： REN Xi-feng SUN Zhao-chen WANG Xing-gang liang shu-xiu State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China Nanjing Hydraulic Research Institute Nanjing 210029China

In this paper, a numerical model of 2D weakly compressible smoothed particle hydrodynamics(WCSPH) is developed to simulate the interaction between waves and thin structures. A new color domain particle(CDP)technique is proposed to overcome difficulties of applying the ghost particle method to thin structures in dealing with solid boundaries. The new technique can deal with zero-thickness structures. To apply this enforcing technique, the computational fluid domain is divided into sub domains, i.e., boundary domains and internal domains. A color value is assigned to each particle, and contains the information of the domains in which the particle belongs to and the particles can interact with. A particle, nearby a thin boundary, is prevented from interacting with particles, which should not interact with on the other side of the structure. It is possible to model thin structures, or the structures with the thickness negligible with this technique. The proposed WCSPH module is validated for a still water tank, divided by a thin plate at the middle section, with different water levels in the subdomains, and is applied to simulate the interaction between regular waves and a perforated vertical plate. Finally, the computation is carried out for waves and submerged twin-horizontal plate interaction. It is shown that the numerical results agree well with experimental data in terms of the pressure distribution, pressure time series and wave transmission.

关键词： SPH CDP thin plate wave–structure interaction

Inverse Calculation of Wave-Absorbing Structure Dimensions Based on Extended ANFIS Model

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China Ocean Engineering 2018年第5期32卷 501-513页

作者： TIAN Zheng-lin SUN Zhao-chen liang shu-xiu WANG Xing-gang The State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China Nanjing Hydraulic Research Institute Nanjing 210029China

A new wave energy dissipation structure is proposed, aiming to optimize the dimensions of the structure and make the reflection of the structure maintain a low level within the scope of the known frequency band. An optimal extended ANFIS model combined with the wave reflection coefficient analysis for the estimation of the structure dimensions is established. In the premise of lower wave reflection coefficient, the specific sizes of the structure are obtained inversely, and the contribution of each related parameter on the structural reflection performance is analyzed. The main influencing factors are determined. It is found that the optimal dimensions of the proposed structure exist, which make the wave absorbing performance of the structure reach a perfect status under a wide wave frequency band.

关键词： new absorbing structure COMBLOC reflected coefficients structural sizes inversion model extended ANFIS

DYNAMIC RESPONSE ANALYSIS OF DDMS PLATFORM SUBJECTED TO ACTIONS OF WAVE GROUPS AND CURRENT FOURCES

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Journal of Hydrodynamics 2011年第6期23卷 697-708页

作者： SUN Zhao-chen WANG Xing-gang liang shu-xiu LIU shu-Xue LIU Si State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024China

Coupled dynamic analysis of the Deep Draft Multi-Spar （DDMS） platform and the mooring system under the action of waves and current is carried out in the time domain. Using a geometrically nonlinear finite element method, the mooring-line dynamics is simulated based on the total Lagrangian formulation. Wave groups are obtained by the JONSWAP spectrum and an empirical wave envelope spectrum involving two envelope-based factors Group Height Factor （GFH） and Group Length Factor （GLF）. The results show that the wave groups have a significant effect on the motion responses of the platform and the mooring line tensions.

关键词： Deep Draft Multi Spar (DDMS) platform dynamic response wave groups current fources

SPECTRAL ANALYSIS OF RANDOM WAVE UPLIFT FORCE ON A HORIZONTAL DECK

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Journal of Hydrodynamics 2011年第1期23卷 81-88页

作者： SUN Jia-wen SUN Zhao-chen liang shu-xiu ZHENG Kun State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024China

This article presents a spectral analysis of wave uplift loads on a horizontal *** wave uplift force spectrum on the underside of the deck is *** is shown that the wave uplift force spectral density decreases with the increase of the relative clearance1/3Δh /*** influences of different incident wave parameters,including the relative wave height1/3H /d,the relativedeck width/sB L and the relative clearance1/3Δh /Hon the dimensionless zeroth spectral moment of the uplift forces *** is found that the zeroth spectral moment of the uplift forces increases with the increase of the relative wave height1/3H /d,and decreases with the increase of the relative clearance1/3Δh /H.A new dimensionless prediction model for the zerothspectral moment of wave uplift loads on the deck is proposed and the relationship between the wave uplift forces and the zerothspectral moment of the uplift force are obtained.

关键词： spectral analysis wave uplift force spectral moment

Experimental Study of Mooring Type Effect on the Hydrodynamic Characteristics of VLFS

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China Ocean Engineering 2022年第1期36卷 155-166页

作者： FENG Ming-wei SUN Zhao-chen liang shu-xiu LI Zhi LV Xuan JIA Song-lin HUXin-yue State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China

Mooring system is a significant part of very large offshore floating structures(VLFS).In this paper,a single module pontoon type VLFS model considering four mooring types is studied through physical model tests to determine the effects of mooring conditions on the hydroelastic response,mooring force,incident coefficient,reflection coefficient and energy dissipation *** mooring cables are symmetrically arranged on both sides of the *** floating body model satisfies the similarity of stiffness and gravity,while the cable satisfies the similarity of elasticity and *** results show that the effect of mooring type on mooring force is greater than that on hydroelastic *** the initial tension of the mooring cable will reduce the amplitude of the leeward of the VLFS *** mooring angle of the mooring cable will affect the maximum mooring force and the initial tension of the mooring line will affect the wave period in which the maximum mooring force *** transmission coefficient and wave energy dissipation coefficient will change regularly with different mooring *** results may provide a reference to facilitate the mooring design of VLFS.

关键词： VLFS hydroelastic response mooring system 3D experimental test mooring force wave reflection coefficient wave transmission coefficient wave dissipation coefficient

A NUMERICAL METHOD FOR NONLINEAR WATER WAVES

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Journal of Hydrodynamics 2009年第3期21卷 401-407页

作者： ZHAO Xi-zeng SUN Zhao-chen liang shu-xiu HU Chang-hong State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China RIAM Kyushu University 6-1 Kasuga-koen Kasuga Fukuoka 816-8580 Japan

This article presents a numerical method for modeling nonlinear water waves based on the High Order Spectral （HOS） method proposed by Dommermuth and Yue and West et al., involving Taylor expansion of the Dirichlet problem and the Fast Fourier Transform （FFT） algorithm. The validation and efficiency of the numerical scheme is illustrated by a number of case studies on wave and wave train configuration including the evolution of fifth-order Stokes waves, wave dispersive focusing and the instability of Stokes wave with finite slope. The results agree well with those obtained by other studies.

关键词： high order spectral method wave focusing wave instability fifth-order Stokes wave Fast Fourier Transform (FFT)