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Nonlinear Numerical Analysis of Vortex-Induced Vibration of A Three-Dimensional Deepwater Steep Wave Riser with Large Deformation Features

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China ocean engineering 2022年第4期36卷 601-613页

作者： CHENG Yong SONG Fu-kai LI Ming-xin School of naval architecture and ocean engineering Jiangsu University of Science and TechnologyZhenjiang 212100China

The cross-flow(CF)vortex-induced vibration(VIV)of a deepwater steep wave riser(SWR)subjected to uniform or shear flow loads is investigated numerically.The model is based on a three-dimensional(3D)nonlinear elastic rod theory coupled with a wake oscillator model.In this numerical simulation,the nonlinear motion equations of the riser with large deformation features are established in a global coordinate system to avoid the transformation between global and local coordinate systems,and are discretized with the time-domain finite element method(FEM).A wakeoscillator model is employed to study the vortex shedding,and the lift force generated by the wake flow is described in a van der Pol equation.A Newmark-βiterative scheme is used to solve their coupling equation for the VIV response of the SWR.The developed model is validated against the existing experimental results for the VIV response of the top-tension riser(TTR).Then,the numerical simulations are executed to determine VIV characteristics of the SWR.The effects of both flow velocity and the spanwise length of the flow field on the drag coefficient in the inline(IL)direction and the lift coefficient in the CF direction are investigated systematically.The results indicate that compared with TTR,the low frequency and multi-modal vibration are the main components of the SWR due to the large deformation and flexible characteristics.For shear flow,the multi-frequency resonance dominates the VIV response of the SWR,especially at the hang-off segment.

关键词： steep wave riser vortex-induced vibration time domain simulation nonlinear finite element wake oscillator

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A fully nonlinear approach for efficient ship-wave simulation

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Journal of Hydrodynamics 2023年第6期35卷 1027-1040页

作者： Kai-yuan Shi Ren-chuan Zhu School of naval architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China

This paper presents an efficient time-domain method for simulating nonlinear ship waves.The proposed method,implemented in an earth-fixed coordinate system,integrates a compact boundary element domain within a high-order spectral layer,enabling accurate modeling of both near-field and far-field ship waves.An overset mesh method and an attention mechanism are employed to track the moving ship.The effectiveness of the method is validated through simulations of Wigley and Series 60 ships sailing at various speeds.The numerical results,including the nonlinear wave run-up at the ship bow,surface pressure distribution on the hull,and the ship resistance,agree well with experimental data and published numerical results,confirming that the method is capable of accurately simulating the nonlinear ship waves.

关键词： Fully nonlinear ship wake potential flow spectral coupled method wave-making resistance

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Hydrodynamic performances and wakes induced by a generic submarine operating near the free surface in continuously stratified fluid

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水动力学研究与进展B辑:英文版 2023年第3期35卷 396-406页

作者： Liu-shuai Cao Gang Gao En-kai Guo De-cheng Wan School of naval architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

The wake of a submarine is a crucial element that greatly affects its stealth and hydrodynamic performance.To investigate the propagation and evolution characteristics of submarine wakes in a stratified fluid,particularly under free surface conditions,a numerical method to simulate the linearly stratified environment was developed.A thermocline model based on Boussinesq assumption was introduced to match the continuously stratified fluid.The volume of fluid(VOF)method was utilized to capture free surface waves,while a fully structured grid and the SST k-ωturbulence model were combined to solve the complex flow of submarines.Grid independence study in homogenous flow near the free surface was initially conducted.Furthermore,the hydrodynamic performance,wake evolution characteristics,free surface signatures as well as decay of velocity under different stratification levels were analyzed.Results demonstrated that the numerical method employed was efficient in simulating stratified flows.Moreover,it showed that density stratification had a significant impact on the hydrodynamics and wake characteristics of a submarine,especially under strong density stratification circumstances.

关键词： Wakes submarine free surface stratified fluid hydrodynamics

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Formula of Overtopping Discharge of Vertical Seawall with A Form Similar to Solitary Wave Function

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China ocean engineering 2022年第5期36卷 802-807页

作者： LI Xiao-liang School of naval architecture&ocean engineering Jiangsu University of Science and TechnologyZhenjiang 212003China

An empirical formula to predict overtopping discharge of vertical wall is presented,in which an expression similar to the solitary wave function is proposed to describe the rule of the influence of relative water depth.The formula is derived from performing an investigation to the well-known overtopping graphs of Goda,and for the sake of interest,the process of the derivation is detailed.To make clear the formula’s performance,relevant test datasets in the CLASH database are extracted to examine the error levels of the formula.As a result,an overall good agreement has been found between the predictions of the formula and the extracted datasets in a wide range outside the extreme shallow region,i.e.,the range of relative water depth smaller than 0.6,in which the water depth near the wall is so shallow that nearly all the incoming waves have been broken before reaching the wall.

关键词： overtopping discharge formula vertical wall Goda graph

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Discussion of the Fluid Acceleration Quality of a Ducted Propulsion System on the Propulsive Performance

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Computer Modeling in engineering & Sciences 2022年第3期130卷 1325-1348页

作者： Jui-Hsiang Kao Yi-Fan Liao Department of Systems engineering and naval architecture Taiwan Ocean UniversityKeelung202301Taiwan

This paper focuses on the ducted propulsion with the accelerating nozzle,and discusses the influence of its fluid acceleration quality on its propulsive performances,including the hull efficiency,the relative rotative efficiency,the effective wake,and the thrust deduction factor.An actual ducted propulsion system is used as an example for computational analysis.The computational conditions are divided into four combinations,which are provided with different propeller pitches,cambers,and duct lengths.Themethod applied in this study is the Computational Fluid Dynamics(CFD)technology,and the contents of the calculation include the hull’s viscous resistance,the wave-making resistance,the propeller performance curve,and the self-propulsion simulation in order to obtain the ship’s effective wake,thrust deduction factor,hull efficiency,and relative rotative efficiency.The performance curve of the propeller and resistance estimation results are compared with the experimental values for determining the correctness of the self-propulsion simulation.According to the computational analysis,it is known that increasing the propeller pitch cannot effectively increase the hull efficiency.The duct acceleration quality can be reduced by shortening the duct length;hence,when the effective wake fraction and thrust deduction factor decrease,the hull efficiency is increased.In addition,the pressure inside the duct is relatively low if the acceleration quality of the duct is too high,which is unfavorable for controlling the propeller cavitation.Moreover,if the hull bottom in front of the propeller is tapered up from the front to the back at an overly steep angle,the thrust deduction factor will be too large and lead to a relatively low hull efficiency.

关键词： Ducted propellers accelerating nozzle hull efficiency relative rotative efficiency effective wake thrust deduction factor

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The capillary pressure curves from upscaling interfacial and unsaturated flows in porous layers with vertical heterogeneity

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Theoretical & Applied Mechanics Letters 2023年第4期13卷 287-290页

作者： Zhong Zheng State Key Laboratory of ocean engineering School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China MOE Key Laboratory of Hydrodynamics School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

We provide the capillary pressure curves p_(c)(s)as a function of the effective saturation s based on the theoretical framework of upscaling unsaturated flows in vertically heterogeneous porous layers proposed recently(Z.Zheng,Journal of Fluid Mechanics,950,A17,2022).Based on the assumption of vertical gravitational-capillary equilibrium,the saturation distribution and profile shape of the invading fluid can be obtained by solving a nonlinear integral-differential equation.The capillary pressure curves p_(c)(s)can then be constructed by systematically varying the injection rate.Together with the relative permeability curves k_(rn)(s)that are already obtained.One can now provide quick estimates on the overall behaviours of interfacial and unsaturated flows in vertically-heterogeneous porous layers.

关键词： Flow upscaling Interfacial and unsaturated flow Wetting and capillary effects Porous layer Heterogeneity

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Numerical Simulation of Sea Ice and Structure Interaction Using Common Node DEM-SPH Model

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China ocean engineering 2023年第6期37卷 897-911页

作者： SHEN Zhong-xiang WANG Wen-qing XU Cheng-yue LI Hong-bin JIANG Yin LIU Ren-wei School of naval architecture and ocean engineering Jiangsu University of Science and TechnologyZhenjiang 212100China college of Harbor Coastal and Offshore EngineeringHohai UniversityNanjing 210098China

In this work,a novel fluid-structure coupling method called the common node discrete element-smoothed particle hydrodynamics(DS-SPH)method is introduced.This framework combines the principles of the common node discrete element method(DEM)and smoothed particle hydrodynamics(SPH)to construct DEM-SPH particles situated on the same node.By doing so,the DEM particles can interact with the SPH particles within their support domain,enabling fluid-structure interaction(FSI).To determine the DEM microscopic parameters required for this method,uniaxial compression and three-point bending tests are conducted on sea ice.To verify the proposed model,we select the interaction between sea ice and structures as a case study.Through simulation,the model's capability of accurately depicting sea ice deformation and fracture has been demonstrated.The results indicate that the inclusion of SPH particles with fluid properties in the DEM model has minimal impact on the main mechanical parameters of sea ice.Additionally,it helps prevent the occurrence of particle splashing during cement failure.However,it is observed that the size of DEM particles and the friction between DEM particles and the structure significantly influence the macroscopic mechanical behavior of the common-node DEM-SPH model.Finally,we compare the fracture behavior of sea ice and the ice forces acting on structures obtained from the current model with on-site measured results.The agreement between the two sets of data is excellent,further validating the effectiveness of the proposed model in practical applications.

关键词： common node DEM-SPH uniaxial compression three-point bending structure-ice interaction

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Experimental investigation and analytically modeling of hysteretic behavior of rigid bus-flexible connectors of 220 kV electrical substations

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Earthquake engineering and engineering Vibration 2023年第3期22卷 841-852页

作者： Tang Tingxuan He Jun Department of Civil engineering School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

This paper describes the quasi-static testing and analytical modelling of the hysteretic behavior of aluminum alloy rigid bus-flexible connectors of 220 kV electrical substations.The main objective of the study is to experimentally investigate the hysteretic behavior of six different types of rigid bus-flexible connectors 220 kV electrical substations when subjected to cyclic loading.Another objective is to theoretically study the flexibility and effectiveness of a previously proposed analytical model in fitting the experimental hysteresis loops of the tested rigid bus-flexible connectors.The experimental investigation indicates that the tested rigid bus-flexible connectors exhibit highly asymmetric hysteresis behavior along with tension stiffening effect.The theoretical study demonstrates that the generalized Bouc-Wen model has high flexibility and is effective in fitting the experimental hysteresis resisting force-displacement curves of the six tested rigid bus-flexible connectors.

关键词： rigid bus-flexible connectors 220 kV electrical substations hysteretic behavior experimental curves analytical model

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Observation of Arctic surface currents using data from a surface drifting buoy

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Acta oceanologica Sinica 2024年第1期43卷 70-79页

作者： Hongxia Chen Lina Lin Long Fan Wangxiao Yang Yinke Dou Bingrui Li Yan He Bin Kong Guangyu Zuo Na Liu First Institute of oceanography Ministry of Natural ResourcesQingdao 266061China Laboratory for Regional oceanography and Numerical Modeling Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China Key Laboratory of Marine Science and Numerical Modeling Ministry of Natural ResourcesQingdao 266061China naval Research Academy Tianjin 300061China college of Electrical and Power engineering Taiyuan University of TechnologyTaiyuan 030024China Polar Research Institute of China Shanghai 443005China

During the 10th Chinese Arctic scientific expedition carried out in the summer of 2019,the surface current in the high-latitude areas of the Arctic ocean was observed using a self-developed surface drifting buoy,which was initially deployed in the Chukchi Sea.The buoy traversed the Chukchi Sea,Chukchi Abyssal Plain,Mendeleev Ridge,Makarov Basin,and Canada Basin over a period of 632 d.After returning to the Mendeleev Ridge,it continued to drift toward the pole.Overall,the track of the buoy reflected the characteristics of the transpolar drift and Chukchi Slope Current,as well as the inertial flow,cross-ridge surface flow,and even the surface disorganized flow for some time intervals.The results showed that:(1)the transpolar drift mainly occurs in the Chukchi Abyssal Plain,Mendeleev Ridge,and western Canada Basin to the east of the ridge where sea ice concentration is high,and the average northward flow velocity in the region between 79.41°N and 86.32°N was 5.1 cm/s;(2)the average surface velocity of the Chukchi Slope Current was 13.5 cm/s,and while this current moves westward along the continental slope,it also extends northwestward across the continental slope and flows to the deep sea;and(3)when sea ice concentration was less than 50%,the inertial flow was more significant(the maximum observed inertial flow was 26 cm/s,and the radius of the inertia circle was 3.6 km).

关键词： Chinese National Arctic Research Expedition(CHINARE) surface drifting buoy transpolar drift Chukchi Slope Current inertial flow

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Structurally coupled characteristics of rotor blade geometrically exact formulation

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Chinese Journal of Aeronautics 2022年第6期35卷 186-197页

作者： Jie WU Yijiang MA Zhidong WANG Zhihao YU School of naval architecture & ocean engineering Jiangsu University of Science and TechnologyZhenjiang 212100China college of Aerospace engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In rotor dynamics,blades are normally modelled as a slender beam,in which elastic deformations are coupled with each other.To identify these coupling effects,new rigid-flexible structural model for helicopter rotor system is proposed in this paper.Finite rotations of the whole blade(on flapwise,lagwise,and torsional)are described as three global rigid degrees of freedom.The nonlinear deformation geometrics of the beam is built on geometrically exact beam theory.New expressions for blade strain energy,kinetic energy,and virtual work of various kinds of external forces are derived as functions of finite rotations and elastic deformations.To quantify the coupling characteristics,following the definition of coupling factor in electromagnetics,a new coupling factor between two modal components on each mode is introduced in modal analysis.Simulations show that the new structural model is highly capable of solving static and dynamic problems in rotor system and the maximum deformation that moderate deformation beam theory can predict might be 15%of beam length.After the new coupling factor is applied to study structurally coupled characteristics of rotor blade,it can be concluded that closeness of natural frequencies likely indicates considerable coupling between corresponding DOFs in structure.

关键词： Computational geometry Flexible couplings Helicopter rotors Modal analysis Structural dynamics

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