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Nonlinear Analysis of Bidirectional Vortex-Induced Vibration of A Deepwater Steep Wave Riser Subjected to Oblique Currents

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China Ocean Engineering 2021年第6期35卷 852-865页

作者： cheng yong TANG Lian-yang JI Chun-yan School of Naval Architecture and Ocean Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China Nippon Kaiji Kyokai(China)Co. LtdShanghai 200336China

An improved three-dimensional(3D)time-domain couple model is established in this paper to simulate the bidirectional vortex-induced vibration(VIV)of a deepwater steep wave riser(SWR)subjected to oblique *** this model,the nonlinear motion equations of the riser are established in the global coordinate system based on the slender rod theory with the finite element *** der Pol equations are used to describe the lift forces induced by the x-and y-direction current components,*** coupled equations at each time step are solved by a Newmark-βiterative scheme for the SWR *** present model is verified by comparison with the published experimental results for a top-tension ***,a series of simulations are executed to determine the influences of the oblique angle/velocity of the current,different top-end positions and the length of the buoyancy segment on the VIV displacement,oscillating frequency as well as hydrodynamic coefficients of the *** results demonstrate that there exists a coupled resonant VIV corresponding to x-direction and y-direction,***,the effective frequency is almost identical between the vibrations at the hang-off segment along x and y *** addition of the buoyancy modules in the middle of the SWR has a beneficial impact on the lift force of three segments and simultaneously limits the VIV response,especially at the decline segment and the hang-off ***,the incident current direction significantly affects the motion trajectory of the SWR which mainly includes the fusiform and rectangle shapes.

关键词： steep wave riser(SWR) bidirectional vortex-induced vibration wake oscillator model time-domain finite element method(TDFEM)

Time-Domain Nonlinear Wave-Current Interaction with A Steep Wave Riser Considering Internal Flow Effect

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China Ocean Engineering 2021年第3期35卷 410-421页

作者： TANG Lian-yang cheng yong JI Chun-yan School of naval architecture and ocean engineering Jiangsu University of Science and TechnologyZhenjiang 212003China Nippon Kaiji Kyokai(China)Co. LtdShanghai 200336China

The nonlinear dynamic response induced by the wave-current interaction on a deepwater steep wave riser(SWR)is numerically investigated based on a three-dimensional(3 D)time-domain finite element method(FEM).The governing equation considering internal flow is established in the global coordinate *** whole SWR consists of three segments:the decline segment,buoyancy segment and hang-off segment,in which the buoyancy segment is wrapped by several buoyancy modules in the middle section,leading to the arch bend and sag bend.A Newmark-β iterative scheme is adopted for the accurate analysis to solve the governing equation and update the dynamic response at each time *** proposed method is verified through the published results for the dynamic response of steel catenary riser(SCR)and static configuration of steel lazy wave riser(SLWR).Simulations are executed to study the influence of wave height,current velocity/direction,internal flow density/velocity and top-end pressure on the tension,configuration and bending moment of the *** results indicate that the influence of the current on the configuration and mechanical behavior of the SWR is greater than that of the wave,especially in the middle *** increasing current velocity,the suspending height of the middle section drops,meanwhile,its bending moment decreases accordingly,but the tension increases *** a fixed external load,the increasing internal flow density induces the amplification of the tension at the hang-off segment and the mitigation at the decline segment,while the opposite trend occurs at the bending moment.

关键词： steep wave riser(SWR) nonlinear dynamic response wave-current interaction time-domain finite element method(FEM)

PopFlow:a novel flow management scheme for SDN switch of multiple flow tables based on flow popularity

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Frontiers of Computer Science 2020年第6期14卷 111-122页

作者： cheng WANG Kyung Tae KIM Hee yong YOUN College of Electrical and Computer Engineering Sungkyunkwan UniversitySuwon 16419Korea College of Software Sungkyunkwan UniversitySuwon 16419Korea

Pipeline processing is applied to mutiple flow tables(MFT)in the switch of software-defined network(SDN)to increase the throughput of the ***,the processing time of each flow increases as the size or number of flow tables gets *** this paper we propose a novel approach called PopFlow where a table keeping popular flow entries is located up front in the pipeline,and an express path is provided for the flow matching the table.A Markov model is employed for the selection of popular entries considering the match latency and match frequency,and Queuing theory is used to model the flow processing time of the existing MFT-based schemes and the proposed *** simulation reveals that the proposed scheme substantially reduces the flow processing time compared to the existing schemes,and the diference gets more significant as the flow arrival rate increases.

关键词： edge computing SDN pipeline processing PopFlow match frequency and latency markov model-based prediction

Application of A Fully Nonlinear Higher-Order Element Method for Modelling Three-Dimensional Wave Entry of A Cone

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China Ocean Engineering 2021年第6期35卷 814-827页

作者： YUAN Dong-chuang cheng yong JI Chun-yan School of Naval Architecture and Ocean Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China

Fully nonlinear water entry of a cone into waves with gravity effect has been analyzed based on a three-dimensional(3D)higher-order boundary method(HOBEM).The total velocity potential at the initial time is divided into the incident and scattering *** the subsequent time steps,the solution of the velocity potential is defined as a whole through instantaneous boundary *** on the image theory,a modified Green function is applied to establish the integral equations so that only half of the calculation domain is considered and the seabed can be *** free surface elevation is tracked along a given azimuth plane in the polar coordinate system,while the horizontal motion of the water particle is updated by using a segment-spring analogy method,which redistributes nodes and maintains mesh connectivity according to linear *** auxiliary function is applied to solve the pressure distribution,instead of directly calculating time derivative of the velocity *** high accuracy of the present numerical method is achieved through a detailed convergence study and comparison with results in the *** are emphatically performed to examine the effects of gravity,wave nonlinearity,entry location,and oblique entry.

关键词： wave entry HOBEM time-domain simulation Green function segment-spring analogy method

Effect of Vacuum Pressure on the Initiation and Propagation of Pitting Corrosion of 2205 duplex Stainless Steel in Concentrated Seawater

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Acta Metallurgica Sinica(English Letters) 2022年第6期35卷 1023-1033页

作者： yong Yang Xue-Ling Hou Mou-cheng Li Institute of Materials School of Materials Science and EngineeringShanghai UniversityShanghai 200072China

Pitting initiation and stable propagation behaviors of 2205 duplex stainless steel were investigated in the hot concentrated seawater under vacuum pressures by potentiostatic polarization. Both applied potentials and vacuum pressures greatly influence the pitting corrosion. Higher potentials lead to much faster stable pitting initiation and growth rates in both static(101.3 kPa) and dynamic(28.4 kPa) solutions. The pressure reduction can also accelerate the pitting initiation rate. However, the boiling of solution can influence the pitting propagation mechanism. The dynamic actions of boiling bubbles are unfavorable to the pit propagation and result in the formation of relatively smooth pit bottom without secondary pits.

关键词： duplex stainless steel Stable pitting Vacuum pressure Hot concentrated seawater Potentiostatic polarization

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 *** model is based on a three-dimensional(3D)nonlinear elastic rod theory coupled with a wake oscillator *** 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 *** 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 *** 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 *** 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 *** 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

A COUPLING MODEL OF WATER FLOWS AND GAS FLOWS IN EXHAUSTED GAS BUBBLE ON MISSILE LAUNCHED UNDERWATER

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Journal of Hydrodynamics 2007年第4期19卷 403-411页

作者： cheng yong-sheng LIU Hua Department of Engineering Mechanics Shanghai Jiaotong University Shanghai 200030 China

The gas and water flows during an underwater missile launch are numerically studied. For the gas flow, the explicit difference scheme of Non-oscillation and Non-free-parameter Dissipation (NND) is utilized to solve the Euler equations for compressible fluids in the body-fitted coordinates. For the water flow, the Hess-Smith method is employed to solve the Laplace equation for the velocity potential of irrotational water flows based on the potential theory and the boundary element method. The hybrid Eulerian-Lagrangian formulation for the free boundary conditions is used to compute the changes of the free surface of the exhausted gas bubble in time stepping. On the free surface of the exhausted gas bubble, the matched conditions of both the normal velocities and pressures are satisfied. From the numerical simulation, it is found that the exhausted gas bubble grows more rapidly in the axial direction than in the radial direction and the bubble will shrink at its "neck" finally. Numerical results of the movement of the shock wave and the distribution of the Mach number and the gas pressure within the bubble were presented, which reveals that at some time, the gas flow in the Laval nozzle is subsonic and the gas pressure in the nozzle is very high. Influences of various initial missile velocities and chamber total pressures and water depths on both the time interval when the gas flow in the nozzle is subsonic and the peak of the gas pressure at the nozzle end were discussed. It was suggested that a reasonable adjustment of the chamber total pressure can improve the performance of the engine during the underwater launch of missiles.

关键词： exhausted gas bubble Laval nozzle missile launched underwater shock wave gas jet

Properties of the phase diagram from the Nambu-Jona-Lasino model with a scalar-vector interaction

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Nuclear Science and Techniques 2024年第10期35卷 168-179页

作者： yong-Hang Yang He Liu Peng-cheng Chu Science School Qingdao University of TechnologyQingdao 266520China The Research Center of Theoretical Physics Qingdao University of TechnologyQingdao 266033China

We investigated the properties of the phase diagram of high-order susceptibilities,speed of sound,and polytropic index based on an extended Nambu-Jona-Lasinio model with an eight-quark scalar-vector ***-monotonic behavior was observed in all these quantities around the phase transition boundary,which also revealed the properties of the critical ***,this study indicated that the chiral phase transition boundary and critical point could vary depending on the scalarvector coupling constant G_(SV).At finite densities and temperatures,the negative G_(SV)term exhibited attractive interactions,which enhanced the critical point temperature and reduced the chemical *** G_(SV)term also affected the properties of the high-order susceptibilities,speed of sound,and polytropic index near the critical *** non-monotonic(peak or dip)structures of these quantities shifted to a low baryon chemical potential(and high temperature)with a negative G_(SV).G_(SV)also changed the amplitude and range of the nonmonotonic ***,the scalar-vector interaction was useful for locating the phase boundary and critical point in QCD phase diagram by comparing the experimental *** study of the non-monotonic behavior of high-order susceptibilities,speed of sound,and polytropic index is of great interest,and further observations related to high-order susceptibilities,speed of sound,and polytropic index being found and applied to the search for critical points in heavy-ion collisions and the study of compact stars are eagerly awaited.

关键词： QCD phase diagram High-order susceptibilities Speed of sound Polytropic index NJL model

W-Band High-Efficiency Waveguide Slot Array Antenna with Low Sidelobe Levels Based on Silicon Micromachining Technology

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Chinese Journal of Electronics 2022年第4期31卷 665-673页

作者： YAO Shisen cheng Yujian BAI Hang FAN yong University of Electronic Science and Technology of China

A high-efficiency waveguide slot array antenna with low sidelobe level(SLL) is investigated for W-band applications. The silicon micromachining technology is utilized to realize multilayer antenna architecture by three key steps of selective etching, gold plating and Au-Au bonding. The radiating slot based on this technique becomes thick with a minimum thickness of 0.2 mm and accompanies with the decrease of slot's radiation ability. To overcome this weakness, a stepped radiation cavity is loaded on the slot. The characteristic of cavityloaded slot is investigated to synthesize the low-SLL array antenna. The unequal hybrid corporate feeding network is constructed to achieve sidelobe suppression in the E-plane. A pair of 16 × 8 low-SLL and high-effciency slot arrays is fashioned and confirmed experimentally. The bandwidth with the radiation effciency higher than 80% is92.3–96.3 GHz. The SLLs in both E-and H-planes are below-19 d B.

关键词： W-band Micromachined waveguide Silicon micromachining Stepped radiation cavity High effciency Sidelobe level (SLL)