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An investigation into natural vibrations of fluid-structure interaction systems subject to Sommerfeld radiation condition

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Acta Mechanica Sinica 2008年第1期24卷 69-82页

作者： jing Tang xing School of Engineering Sciences University of Southampton Southampton SO17 1B J England

A fluid-structure interaction system subject to Sommerfeld＇s condition is defined as a Sommerfeld system which is divided into three categories： Fluid Sommerfeld （FS） System, Solid Sommerfeld （SS） System and Fluid Solid Sommerfeld （FSS） System of which Sommerfeld conditions are imposed on a fluid boundary only, a solid boundary only and both fluid and solid boundaries, respectively. This paper follows the previous initial results claimed by simple examples to further mathematically investigate the natural vibrations of generalized Sommerfeld systems. A new parameter representing the speed of radiation wave for generalized 3-D problems with more complicated boundary conditions is introduced into the Sommerfeld condition which allows investigation of the natural vibrations of a Sommerfeld system involving both free surface and compressible waves. The mathematical demonstrations and selected examples confirm and reveal the natural behaviour of generalized Sommerfeld systems defined above. These generalized conclusions can be used in theoretical or engineering analysis of the vibrations of various Sommerfeld systems in engineering.

关键词： Sommerfeld system Complex natural frequencies Fluid-structure interaction Complex energyflow identity Speed of radiation wave

Generalised energy conservation law for chaotic phenomena

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Acta Mechanica Sinica 2019年第6期35卷 1257-1268页

作者： jing-Tang xing Faculty of Engineering and Physical Sciences University of SouthamptonSouthampton SO171BJUK

Chaotic phenomena are increasingly being observed in all fields of nature,where investigations reveal that a natural phe nomenon exhibits nonlinearities and attempts to reveal their deep underlying *** is normally understood as“a state of disorder”,for which there is as yet no universally accepted mathematical definition.A commonly used concept states that,for a dynamical system to be classified as chaotic,it must have the following properties:be sensitive to initial conditions,show topological transitivity,have densely periodical orbits *** the rules that govern chaotic motion is thus an important unsolved task for exploring nature.W e present herein a generalised energy conservation law governing chaotic *** on two scalar variables,*** potential and kinetic energies defined in the phase space describing nonlinear dynamical systems,we find that chaotic motion is periodic motion with infinite time period whose time-averaged generalised potential and kinetic energies are conserved over its time *** implies that,as the averaging time is increased,the time-averaged generalised potential and kinetic energies tend to constants while the time-averaged energy flows,i.e.,their rates of change with time,tend to *** simulations on reported chaotic motions,such as the forced van der Pol system,forced Duffing system,forced smooth and discontinuous oscillator,Lorenz’s system,and Rossler's system,show the above conclusions to be correct according to the results presented *** discovery may indicate that chaotic phenomena in nature could be controlled because,even though their instantaneous states are disordered,their long-time averages can be predicted.

关键词： Chaos Generalised energy Generalised energy conservation Nonlinear dynamical systems Energy flow theory

Energy flow characteristics of friction-induced nonlinear vibrations in a water-lubricated bearing-shaft coupled system

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Acta Mechanica Sinica 2021年第4期37卷 679-704,I0003页

作者： Li Qin Hongling Qin jing Tang xing Key Laboratory of Metallurgical Equipment and Control Technology School of Machinery&AutomationWuhan University of Science and TechnologyWuhan 430081China Hubei Key Laboratory of Hydroelectric Machinery Design&Maintenance Three Gorges UniversityYichang 443002China Maritime Engineering Group CMEESchool of EngineeringFaculty of Engineering&Physical SciencesUniversity of SouthamptonSouthampton SO 171BJUK

Based on the energy flow theory of nonlinear dynamical system,the stabilities,bifurcations,possible periodical/chaotic motions of nonlinear water-lubricated bearing-shaft coupled systems are investigated in this *** is revealed that the energy flow characteristics around the equlibrium point of system behaving in the three types with different friction-para-mters.(a)Energy flow matrix has two negative and one positive energy flow factors,constructing an attractive local zero-energy flow surface,in which free vibrations by initial disturbances show damped modulated oscillations with the system tending its equlibrium state,while forced vibrations by external forces show stable oscillations,(b)Energy flow matrix has one negative and two positive energy flow factors,spaning a divergence local zero-energy flow surface,so that the both free and forced vibrations are divergence oscillations with the system being unstable,(c)Energy flow matrix has a zero-energy flow factor and two opposite factors,which constructes a local zero-energy flow surface dividing the local phase space into stable,unstable and central subspace,and the simulation shows friction self-induced unstable vibrations for both free and forced *** a set of friction parameters,the system behaves a periodical oscillation,where the bearing motion tends zero and the shaft motion reaches a stable limit circle in phase space with the instant energy flow tending a constant and the time averaged one tending *** simulations have not found any possible chaotic motions of the *** is discovered that the damping matrices of cases(a),(b)and(c)respectively have positive,negative and zero diagonal elements,resulting in the different dynamic behavour of system,which gives a giderline to design the water-lubricated bearing unit with expected performance by adjusting the friction parameters for applications.

关键词： Nonlinear friction-induced vibrations Nonlinear energy flows Nonlinear water-lubricated bearing-shaft systems Bifucation friction parameters Energy flow matrices Periodical oscilation

GEANT4 simulation of water volume fraction measurement in dehydrated crude oil

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Nuclear Science and Techniques 2007年第4期18卷 198-203页

作者： jing Chunguo xing Guangzhong LIU Bin College of Electric Engineering Yanshan University Qinhuangdao 066004 China

Online measurement of water volume fraction (WVF) in dehydrated crude oil is a difficult task due to very little water in dehydrated crude oil and high precision requirements. We presents a method to measure water volume fraction in dehydrated crude oil with γ-ray densitometry. The Monte Carlo computer simulation packet GEANT4 was used to analyze the WVF measuring sensitivity of the γ-ray densitometry at different γ-ray energies, and effects of temperature, pressure, salinity and oil components on WVF measurement. The results show that the γ-ray densitometry has high sensitivity in γ-ray energy ranges of 16~25keV, and it can distinguish WVF changes of 0.0005. The calculated WVF decreases about 0.0002 with 1℃ of temperature increase and they have approximately linear relation with temperature when water volume fraction remains the same. Effects of pressure, salinity and oil components on water volume fraction can be neglected. Experiments were done to analyze sensitivity of the γ-ray densitometry. The results , as compared with simulations, demonstrate that simulation method is reliable and it is feasible to gauge low water volume fraction using low energy γ-rays.

关键词：石油脱水含水率密度测试

Mei Symmetry and Lutzky Conserved Quantity for Nonholonomic Mechanical System with Unilateral Constraints

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Communications in Theoretical Physics 2008年第3期49卷 575-578页

作者： jing Hong-xing LI Yuan-Cheng College of Physics Science and Technology China University of Petroleum （East China） Dongying 257061 China

In this paper, we study the Mei symmetry which can result in a Lutzky conserved quantity for nonholonomic mechanical system with unilateral constraints. The definition and the criterion of the Mei symmetry for the system are given. The necessary and sufficient condition under which the Mei symmetry is a Lie symmetry for the system is obtained. A Lutzky conserved quantity deduced from the Mei symmetry is gotten. An example is given to illustrate the application of our results.

关键词： nonholonomic mechanical system unilateral constraint Mei symmetry Lutzky conserved quantity

Lie Symmetry and Conserved Quantities for Mechanical-Electrical Systems

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Communications in Theoretical Physics 2008年第6期49卷 1417-1420页

作者： jing Hong-xing LI Yuan-Cheng College of Physics Science and Technology China University of Petroleum （East China） Dongying 257061 China

In this paper, we study Lie symmetry and conserved quantities for a mechanical-electrical system. The criterion of the Lie symmetry for this system is given. The generalized Hojman conserved quantity and generalized Lutzky conserved quantity deduced from the Lie symmetry for the system are obtained. An example is presented to illustrate the results.

关键词： mechanical-electrical system Lie symmetry generalized Hojman conserved quantity, generalized Lutzky conserved quantity

Lie Symmetry and Generalized Mei Conserved Quantity for Nonconservative Dynamical System

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Communications in Theoretical Physics 2008年第5期49卷 1148-1150页

作者： jing Hong-xing LI Yuan-Cheng College of Physical Science and Technology China University of Petroleum （East China） Dongying 257061 China

Based on the total time derivative along the trajectory of the system, for noneonservative dynamical system, the generalized Mei conserved quantity indirectly deduced from the Lie symmetry of the system is studied. Firstly, the Lie symmetry of the system is given. Then, the necessary and sumeient condition under which the Lie symmetry is a Mei symmetry is presented and the generalized Mei conserved quantity indirectly deduced from the Lie symmetry of the system is obtained. Lastly, an example is given to illustrate the application of the result.

关键词： Lie symmetry Mei symmetry generalized Mei conserved quantity nonconservative dynamicalsystem

Dynamic interactions of an integrated vehicle–electromagnetic energy harvester–tire system subject to uneven road excitations

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Acta Mechanica Sinica 2017年第2期33卷 440-456页

作者： jing Tang xing Zhe Sun Sulian Zhou Mingyi Tan Fluid Structure Interactions Group FEEUniversity of Southampton College of Shipbuilding Engineering Harbin Engineering University

An investigation is undertaken of an integrated mechanical-electromagnetic coupling system consisting of a rigid vehicle with heave, roll, and pitch motions, four electromagnetic energy harvesters and four tires subject to uneven road excitations in order to improve the passengers' riding comfort and harvest the lost engine energy due to uneven roads. Following the derived mathematical formulations and the proposed solution approaches, the numerical simulations of this interaction system subject to a continuous sinusoidal road excitation and a single ramp impact are completed. The simulation results are presented as the dynamic response curves in the forms of the frequency spectrum and the time history, which reveals the complex interaction characteristics of the system for vibration reductions and energy harvesting performance. It has addressed the coupling effects on the dynamic characteristics of the integrated system caused by: (1) the natural modes and frequencies of the vehicle; (2) the vehicle rolling and pitching motions; (3) different road excitations on four wheels; (4) the time delay of a road ramp to impact both the front and rear wheels, etc., which cannot be tackled by an often used quarter vehicle model. The guidelines for engineering applications are given. The developed coupling model and the revealed concept provide a means with analysis idea to investigate the details of four energy harvester motions for electromagnetic suspension designs in order to replace the current passive vehicle isolators and to harvest the lost engine energy. Potential further research directions are suggested for readers to consider in the future.

关键词： Vibration-energy-harvesters Electromagnetic suspensions Mechanical electromagnetic interactions Vehicle dynamics Vibration isolations

WELD ROOT MAGNIFICATION FACTORS FOR SEMI-ELLIPTICAL CRACKS IN T-BUTT JOINTS

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Acta Mechanica Solida Sinica 2013年第3期26卷 317-330页

作者： Zhanxun Song Yeping Xiong Jilong Xie jing Tang xing School of Mechanical Electronic & Control EngineeringBeijing Jiaotong University Faculty of Engineering & the Environments Fluid-Structure Interaction Research GroupUniversity of Southampton

Many researchers have focused their efforts on fatigue failures occurring on weld toes. In recent years, more and more fatigue failures occur on weld roots. Therefore, it is important to explore the behaviour of weld root fatigues. This paper investigates numerically the Magnification factors （Mk） for types of semi-elliptical cracks on the weld root of a T-butt joint. The geometry of the joint is determined by four important parameters： crack depth ratio, crack shape ratio, weld leg ratio and weld angle. A singular element approach is used to generate the corresponding finite element meshes. For each set of given four parameters of the semi-elliptical root crack, the corresponding T-butt joint is numerically simulated and its Mk at the deepest point of the weld root crack is obtained for the respective tension and shear loads. The variation range of the four parameters covers 750 cases for each load, totaling 1500 simulations are completed. The numerical results obtained are then represented by the curve to explore the effects of four parameters on the Mk. To obtain an approximate equation representing Mk as a function of the four parameters for each load, a multiple regression method is adopted and the related regression analysis is performed. The error distributions of the two approximate equations are compared with the finite element data. It is confirmed that the obtained approximate functions fit very well to the database from which they are derived. Therefore, these two equations present a valuable reference for engineering applications in T-butt joint designs.

关键词： welded root cracks singular element method stress intensity factors magnificationfactors multiple regressions