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Horizontal Slow Oscillation of a Moored Tanker and Numerical Method of Hopf-Bifurcation
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作者 Chen, Shaohua Sun, Mingguang 《China Ocean Engineering》 SCIE EI 1993年第4期383-400,共18页
In this paper, a six-order nonlinear dynamic model with three degrees of freedom is presented for the study of the 'fishtail' motion of a Single Point Mooring System. The effect of parameter variations on the ... In this paper, a six-order nonlinear dynamic model with three degrees of freedom is presented for the study of the 'fishtail' motion of a Single Point Mooring System. The effect of parameter variations on the equilibrium state of the system is analyzed. In order to study the stability of the equilibrium state, the mooring-line length l is chosen as a bifurcation parameter, so that all eigenvalues of the Jacobian matrix under different parameters can be worked out, and then the Hopf-bifurcation point can be found. Finally, the Hopf-bifurcation periodic solution of the system is computed. 展开更多
关键词 Degrees of freedom (mechanics) Eigenvalues and eigenfunctions Mathematical models Matrix algebra numerical methods oscillations System stability Tankers (ships)
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Numerical Stability and Oscillations of Runge-Kutta Methods for Differential Equations with Piecewise Constant Arguments of Advanced Type
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作者 Wang Qi Ma Fu-ming 《Communications in Mathematical Research》 CSCD 2013年第2期131-142,共12页
For differential equations with piecewise constant arguments of advanced type, numerical stability and oscillations of Runge-Kutta methods are investigated. The necessary and sufficient conditions under which the nume... For differential equations with piecewise constant arguments of advanced type, numerical stability and oscillations of Runge-Kutta methods are investigated. The necessary and sufficient conditions under which the numerical stability region contains the analytic stability region are given. The conditions of oscillations for the Runge-Kutta methods are obtained also. We prove that the Runge-Kutta methods preserve the oscillations of the analytic solution. Moreover, the relationship between stability and oscillations is discussed. Several numerical examples which confirm the results of our analysis are presented. 展开更多
关键词 numerical solution Runge-Kutta method asymptotic stability oscillation
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Universality of Periodic Oscillation Induced in Side Branch of a T-Junction in Numerical Simulation 被引量:1
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作者 Ryuhei Yamaguchi Gaku Tanaka +3 位作者 Tadashi Nakagawa Atsushi Shirai Hao Liu Toshiyuki Hayase 《Journal of Flow Control, Measurement & Visualization》 2017年第4期73-85,共13页
The flow instability through the side branch of a T-junction is analyzed in a numerical simulation. In a previous experimental study, the authors clarified the mechanism of fluid-induced vibration in the side branch o... The flow instability through the side branch of a T-junction is analyzed in a numerical simulation. In a previous experimental study, the authors clarified the mechanism of fluid-induced vibration in the side branch of the T-junction in laminar steady flow through the trunk. However, in that approach there were restrictions with respect to extracting details of flow behavior such as the flow instability and the distribution of wall shear stress along the wall. Here the spatial growth of the velocity perturbation at the upstream boundary of the side branch is investigated. The simulation result indicates that a periodic velocity fluctuation introduced at the upstream boundary is amplified downstream, in good agreement with experimental result. The fluctuation in wall shear stress because of the flow instability shows local extrema in both the near and distal walls. From the numerical simulation, the downstream fluid oscillation under a typical condition has a Strouhal number of 1.05, which approximately agrees with the value obtained in experiments. Therefore, this periodic oscillation motion is a universal phenomenon in the side branch of a T-junction. 展开更多
关键词 Flow INSTABILITY Fluid-Induced oscillation numerical Simulation SIMPLER method T-JUNCTION
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Reduction of Numerical Oscillations in Simulating Moving-Boundary Problems by the Local DFD Method 被引量:1
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作者 Yang Zhang Chunhua Zhou 《Advances in Applied Mathematics and Mechanics》 SCIE 2016年第1期145-165,共21页
In this work,the hybrid solution reconstruction formulation proposed by Luo et al.[H.Luo,H.Dai,P.F.de Sousa and B.Yin,On the numerical oscillation of the direct-forcing immersed-boundary method for moving boundaries,C... In this work,the hybrid solution reconstruction formulation proposed by Luo et al.[H.Luo,H.Dai,P.F.de Sousa and B.Yin,On the numerical oscillation of the direct-forcing immersed-boundary method for moving boundaries,Computers&Fluids,56(2012),pp.61–76]for the finite-difference discretization on Cartesian meshes is implemented in the finite-element framework of the local domain-free discretization(DFD)method to reduce the numerical oscillations in the simulation of movingboundary flows.The reconstruction formulation is applied at fluid nodes in the immediate vicinity of the immersed boundary,which combines weightly the local DFD solution with the specific values obtained via an approximation of quadratic polynomial in the normal direction to the wall.The quadratic approximation is associated with the no-slip boundary condition and the local simplified momentum equation.The weighted factor suitable for unstructured triangular and tetrahedral meshes is constructed,which is related to the local mesh intervals near the immersed boundary and the distances from exterior dependent nodes to the boundary.Therefore,the reconstructed solution can account for the smooth movement of the immersed boundary.Several numerical experiments have been conducted for two-and three-dimensional moving-boundary flows.It is shown that the hybrid reconstruction approach can work well in the finite-element context and effectively reduce the numerical oscillations with little additional computational cost,and the spatial accuracy of the original local DFD method can also be preserved. 展开更多
关键词 numerical oscillation immersed boundary method moving boundary domain-free discretization boundary condition
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Hermite Finite Element Method for Vibration Problem of Euler-Bernoulli Beam on Viscoelastic Pasternak Foundation
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作者 Pengfei Ji Zhe Yin 《Engineering(科研)》 2024年第10期337-352,共16页
Viscoelastic foundation plays a very important role in civil engineering. It can effectively disperse the structural load into the foundation soil and avoid the damage caused by the concentrated load. The model of Eul... Viscoelastic foundation plays a very important role in civil engineering. It can effectively disperse the structural load into the foundation soil and avoid the damage caused by the concentrated load. The model of Euler-Bernoulli beam on viscoelastic Pasternak foundation can be used to analyze the deformation and response of buildings under complex geological conditions. In this paper, we use Hermite finite element method to get the numerical approximation scheme for the vibration equation of viscoelastic Pasternak foundation beam. Convergence and error estimation are rigourously established. We prove that the fully discrete scheme has convergence order O(τ2+h4), where τis time step size and his space step size. Finally, we give four numerical examples to verify the validity of theoretical analysis. 展开更多
关键词 Viscoelastic Pasternak Foundation Beam vibration Equation Hermite Finite Element method Error Estimation numerical Simulation
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Numerical and test study on vertical vibration characteristics of pile group in slope soil topography 被引量:7
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作者 Qu Liming Ding Xuanming +2 位作者 Zheng Changjie Wu Chongrong Cao Guangwei 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2021年第2期377-390,共14页
Topography effects on the vertical vibration responses of pile group are revealed though numerical analysis and model tests.First,a series of model tests with different topography of ground and bedrock are conducted.T... Topography effects on the vertical vibration responses of pile group are revealed though numerical analysis and model tests.First,a series of model tests with different topography of ground and bedrock are conducted.The results indicate that displacement amplitude of the pile head in sloping ground topography is larger than in horizontal ground.Differential displacement at various positions of the pile cap is observed in non-horizontal topography.Afterwards,a numerical algorithm is employed to further explore the essential response characteristics in group piles of different topography configurations,which has been verified by the test results.The lengths of the exposed and frictional segment,together with the thickness of the subsoil layer,are the dominant factors which cause non-axisymmetric vibration at the pile cap. 展开更多
关键词 topography effects pile group vibration response model test numerical method
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Benchmarking of two three-dimensional numerical models in time/space domain to predict railway-induced ground vibrations 被引量:2
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作者 Jesus Fernandez-Ruiz Luis E.Medina Rodriguez +1 位作者 Pedro Alves Costa Margarita Martinez-Diaz 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2021年第1期245-256,共12页
In the last 30 years,the scientific community has developed and proposed different models and numerical approaches for the study of vibrations induced by railway traffic.Most of them are formulated in the frequency/wa... In the last 30 years,the scientific community has developed and proposed different models and numerical approaches for the study of vibrations induced by railway traffic.Most of them are formulated in the frequency/wave number domain and with a 2.5D approach.Three-dimensional numerical models formulated in the time/space domain are less frequently used,mainly due to their high computational cost.Notwithstanding,these models present very attractive characteristics,such as the possibility of considering nonlinear behaviors or the modelling of excess pore pressure and non-homogeneous and non-periodic geometries in the longitudinal direction of the track.In this study,two 3D numerical approaches formulated in the time/space domain are compared and experimentally validated.The first one consists of a finite element approach and the second one of a finite difference approach.The experimental validation in an actual case situated in Carregado(Portugal)shows an acceptable fitting between the numerical results and the actual measurements for both models.However,there are some differences among them.This study therefore includes some recommendations for their use in practical soil dynamics and geotechnical engineering. 展开更多
关键词 railway vibrations time/space domain 3D numerical model finite difference method implicit finite element method
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Numerical Integration of Forced and Damped Oscillators through a New Multistep Method
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作者 M. Cortés-Molina F. García-Alonso J. A. Reyes 《Journal of Applied Mathematics and Physics》 2019年第10期2440-2458,共19页
Forced and damped oscillators appear in the mathematical modelling of many problems in pure and applied sciences such as physics, engineering and celestial mechanics among others. Although the accuracy of the T-functi... Forced and damped oscillators appear in the mathematical modelling of many problems in pure and applied sciences such as physics, engineering and celestial mechanics among others. Although the accuracy of the T-functions series method is high, the calculus of their coefficients needs specific recurrences in each case. To avoid this inconvenience, the T-functions series method is transformed into a multistep method whose coefficients are calculated using recurrence procedures. These methods are convergent and have the same properties to the T-functions series method. Numerical examples already used by other authors are presented, such as a stiff problem, a Duffing oscillator and an equatorial satellite problem when the perturbation comes from zonal harmonics J2. 展开更多
关键词 numerical Solutions of ODE’s PERTURBED and DAMPED oscillators Initial Value Problems (IVP) MULTISTEP methods
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NUMERICAL METHOD FOR SOLVING THE EULER EQUATION FOR UNSTEADY TRANSONIC FLOWS OVER OSCILLATING AIRFOILS
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作者 Li FengweiNorthwestern Polytechnical University 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 1991年第1期1-10,共10页
Through transformations, the time-dependent boundary condition on the airfoil contour and the boundary condition at infinity are brought fixed to the boundaries of a finite domain. The boundary conditions can thus be ... Through transformations, the time-dependent boundary condition on the airfoil contour and the boundary condition at infinity are brought fixed to the boundaries of a finite domain. The boundary conditions can thus be satisfied exactly without increasing the computational time. The novel scheme is useful for computing transonic, strong disturbance, unsteady flows with high reduced frequencies. The scheme makes use of curvefitted orthogonal meshes and the lattice control technique to obtain the optimal grid distribution. The numerical results are satisfactory. 展开更多
关键词 numerical method FOR SOLVING THE EULER EQUATION FOR UNSTEADY TRANSONIC FLOWS OVER oscilLATING AIRFOILS FLOW NACA
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Fully coupled flow-induced vibration of structures under small deformation with GMRES method 被引量:2
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作者 张立翔 郭亚昆 张洪明 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2010年第1期87-96,共10页
Lagrangian-Eulerian formulations based on a generalized variational principle of fluid-solid coupling dynamics are established to describe flow-induced vibration of a structure under small deformation in an incompress... Lagrangian-Eulerian formulations based on a generalized variational principle of fluid-solid coupling dynamics are established to describe flow-induced vibration of a structure under small deformation in an incompressible viscous fluid flow. The spatial discretization of the formulations is based on the multi-linear interpolating functions by using the finite element method for both the fluid and solid structures. The generalized trapezoidal rule is used to obtain apparently non-symmetric linear equations in an incremental form for the variables of the flow and vibration. The nonlinear convective term and time factors are contained in the non-symmetric coefficient matrix of the equations. The generalized minimum residual (GMRES) method is used to solve the incremental equations. A new stable algorithm of GMRES-Hughes-Newmark is developed to deal with the flow-induced vibration with dynamical fluid-structure interaction in complex geometries. Good agreement between the simulations and laboratory measurements of the pressure and blade vibration accelerations in a hydro turbine passage was obtained, indicating that the GiViRES-Hughes-Newmark algorithm presented in this paper is suitable for dealing with the flow-induced vibration of structures under small deformation. 展开更多
关键词 flow-induced vibration fluid-structure interaction generalized variationalprinciple numerical methods generalized minimum residual (GMRES) method
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Torsional Vibration of Roller Oscillating Tooth Gear Drive 被引量:1
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作者 李瑰贤 杨伟君 +2 位作者 李笑 刘福利 顾晓华 《Journal of Donghua University(English Edition)》 EI CAS 2002年第2期69-73,共5页
Torsional vibration of roller oscillating tooth gear drive (ROTGD) is studied in this paper. On the basis of conservation law for kinetic energy and potential energy, the mathematical expressions are developed which d... Torsional vibration of roller oscillating tooth gear drive (ROTGD) is studied in this paper. On the basis of conservation law for kinetic energy and potential energy, the mathematical expressions are developed which describe transformation of moment of inertia of inertial components into input shaft. Also, the formula is derived which expresses transformation of contact stiffness of elastic components into input shaft torsional stiffness. Besides, torsional vibration model of ROTGD is presented by using the transfer matrix method, and natural frequencies and vibration mode shapes are determined. Eventually, an example is given. 展开更多
关键词 ROLLER oscilLATING TOOTH GEAR drive Torsional vibration TRANSFER matrix method
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Second-order two-scale analysis and numerical algorithms for the hyperbolic–parabolic equations with rapidly oscillating coefficients
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作者 董灏 聂玉峰 +1 位作者 崔俊芝 武亚涛 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第9期40-53,共14页
We study the hyperbolic–parabolic equations with rapidly oscillating coefficients. The formal second-order two-scale asymptotic expansion solutions are constructed by the multiscale asymptotic analysis. In addition, ... We study the hyperbolic–parabolic equations with rapidly oscillating coefficients. The formal second-order two-scale asymptotic expansion solutions are constructed by the multiscale asymptotic analysis. In addition, we theoretically explain the importance of the second-order two-scale solution by the error analysis in the pointwise sense. The associated explicit convergence rates are also obtained. Then a second-order two-scale numerical method based on the Newmark scheme is presented to solve the equations. Finally, some numerical examples are used to verify the effectiveness and efficiency of the multiscale numerical algorithm we proposed. 展开更多
关键词 hyperbolic–parabolic equations rapidly oscillating coefficients second-order two-scale numerical method Newmark scheme
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Mixed Finite Volume Element Method for Vibration Equations of Beam with Structural Damping
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作者 Tongxin Wang Ziwen Jiang Zhe Yin 《American Journal of Computational Mathematics》 2021年第3期207-225,共19页
<span style="font-family:Verdana;">In this paper, for the initial and boundary value problem of beams with</span> <span style="font-family:Verdana;">structural damping, by introdu... <span style="font-family:Verdana;">In this paper, for the initial and boundary value problem of beams with</span> <span style="font-family:Verdana;">structural damping, by introducing intermediate variables, the original </span><span style="font-family:Verdana;">fourth-order problem is transformed into second-order partial differential equations, and the mixed finite volume element scheme is constructed, and the existence, uniqueness and convergence of the scheme are analyzed</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span><span><span><span style="font-family:Verdana;"> Numerical examples are provided to confirm the theoretical results. In the end, we test the value of <em>δ</em></span><span style="font-family:Verdana;"> to observe its influence on the model.</span></span></span> 展开更多
关键词 vibration Equations Structural Damping Mixed Finite Volume Element method Error Estimation numerical Simulation
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Nonlinear integral resonant controller for vibration reduction in nonlinear systems 被引量:1
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作者 Ehsan Omidi S.Nima Mahmoodi 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2016年第5期925-934,共10页
A new nonlinear integral resonant controller(NIRC) is introduced in this paper to suppress vibration in nonlinear oscillatory smart structures. The NIRC consists of a first-order resonant integrator that provides ad... A new nonlinear integral resonant controller(NIRC) is introduced in this paper to suppress vibration in nonlinear oscillatory smart structures. The NIRC consists of a first-order resonant integrator that provides additional damping in a closed-loop system response to reduce highamplitude nonlinear vibration around the fundamental resonance frequency. The method of multiple scales is used to obtain an approximate solution for the closed-loop system.Then closed-loop system stability is investigated using the resulting modulation equation. Finally, the effects of different control system parameters are illustrated and an approximate solution response is verified via numerical simulation results.The advantages and disadvantages of the proposed controller are presented and extensively discussed in the results. The controlled system via the NIRC shows no high-amplitude peaks in the neighboring frequencies of the resonant mode,unlike conventional second-order compensation methods.This makes the NIRC controlled system robust to excitation frequency variations. 展开更多
关键词 Active vibration control CANTILEVER Highamplitude oscillation method of multiple scales Nonlinear vibration Piezoelectric actuator Smart structure
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Numerical simulations for MHD coronal seismology
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作者 David James Pascoe 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2014年第7期805-830,共26页
Magnetohydrodynamic(MHD) processes are important for the transfer of energy over large scales in plasmas and so are essential to understanding most forms of dynamical activity in the solar atmosphere. The introducti... Magnetohydrodynamic(MHD) processes are important for the transfer of energy over large scales in plasmas and so are essential to understanding most forms of dynamical activity in the solar atmosphere. The introduction of transverse structuring into models for the corona modifies the behavior of MHD waves through processes such as dispersion and mode coupling. Exploiting our understanding of MHD waves with the diagnostic tool of coronal seismology relies upon the development of sufficiently detailed models to account for all the features in observations. The development of realistic models appropriate for highly structured and dynamical plasmas is often beyond the domain of simple mathematical analysis and so numerical methods are employed. This paper reviews recent numerical results for seismology of the solar corona using MHD. 展开更多
关键词 MHD -- methods: numerical -- Sun: corona -- Sun: magnetic fields --Sun: oscillations -- waves
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Implementation of a particle-in-cell method for the energy solver in 3D spherical geodynamic modeling
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作者 Hao Dong ZeBin Cao +4 位作者 LiJun Liu YanChong Li SanZhong Li LiMing Dai XinYu Li 《Earth and Planetary Physics》 EI CAS CSCD 2024年第3期549-563,共15页
The thermal evolution of the Earth’s interior and its dynamic effects are the focus of Earth sciences.However,the commonly adopted grid-based temperature solver is usually prone to numerical oscillations,especially i... The thermal evolution of the Earth’s interior and its dynamic effects are the focus of Earth sciences.However,the commonly adopted grid-based temperature solver is usually prone to numerical oscillations,especially in the presence of sharp thermal gradients,such as when modeling subducting slabs and rising plumes.This phenomenon prohibits the correct representation of thermal evolution and may cause incorrect implications of geodynamic processes.After examining several approaches for removing these numerical oscillations,we show that the Lagrangian method provides an ideal way to solve this problem.In this study,we propose a particle-in-cell method as a strategy for improving the solution to the energy equation and demonstrate its effectiveness in both one-dimensional and three-dimensional thermal problems,as well as in a global spherical simulation with data assimilation.We have implemented this method in the open-source finite-element code CitcomS,which features a spherical coordinate system,distributed memory parallel computing,and data assimilation algorithms. 展开更多
关键词 numerical oscillation overshooting and undershooting particle-in-cell method three-dimensional spherical geodynamic modeling energy solver finite element method
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Nonlinear Response of Tunnel Portal under Earthquake Waves with Different Vibration Directions
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作者 Hongyun Jiao Mi Zhao +2 位作者 Jingqi Huang Xu Zhao Xiuli Du 《Computer Modeling in Engineering & Sciences》 SCIE EI 2022年第6期1289-1314,共26页
Tunnel portal sections often suffer serious damage in strong earthquake events.Earthquake waves may propagate in different directions,producing various dynamic responses in the tunnel portal.Based on the Galongla tunn... Tunnel portal sections often suffer serious damage in strong earthquake events.Earthquake waves may propagate in different directions,producing various dynamic responses in the tunnel portal.Based on the Galongla tunnel,which is located in a seismic region of China,three-dimensional seismic analysis is conducted to investigate the dynamic response of a tunnel portal subjected to earthquake waves with different vibration directions.In order to simulate the mechanic behavior of slope rock effectively,an elastoplastic damage model is adopted and applied to ABAQUS software by a self-compiled user material(UMAT)subroutine.Moreover,the seismic wave input method for tunnel portal is established to realize the seismic input under vertically incident earthquake waves with different vibration directions,e.g.,S waves with a vibration direction perpendicular or parallel to the tunnel axis and P waves with a vibration direction perpendicular to the tunnel axis.The numerical results indicate that the seismic response and damage mechanisms of the tunnel portal section are related to the vibration direction of the earthquake waves.For vertically incident S waves running perpendicular to the tunnel axis,the hoop tensile strain at the spandrel and arch foot and the hoop shear strain at the vault and arch bottom are the main contributors to the plastic damage of the tunnel.The strain is initially concentrated around the tunnel foot and spandrel,before shifting to the tunnel vault and bottom farther away from the tunnel entrance.For vertically incident S waves running parallel to the tunnel axis,very large hoop shear strain and plastic damage appear at the tunnel haunches.This strain first increases and then decreases with distance from the tunnel entrance.For vertically incident P waves running perpendicular to the tunnel axis,the maximum damage factor of the slope rock and the maximum plastic strain of the tunnel are significantly lower than for S waves.Moreover,with increasing distance from the tunnel entrance,the plastic damage to the tunnel lining rapidly decreases. 展开更多
关键词 Tunnel portal EARTHQUAKE dynamic numerical analysis vibration direction elastoplastic damage model seismic input method
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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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作者 CHENG Yong TANG Lian-yang JI Chun-yan 《China Ocean Engineering》 SCIE EI CSCD 2021年第6期852-865,共14页
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 currents.In th... 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 currents.In 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 method.Van der Pol equations are used to describe the lift forces induced by the x-and y-direction current components,respectively.The coupled equations at each time step are solved by a Newmark-βiterative scheme for the SWR VIV.The present model is verified by comparison with the published experimental results for a top-tension riser.Then,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 SWR.The results demonstrate that there exists a coupled resonant VIV corresponding to x-direction and y-direction,respectively.However,the effective frequency is almost identical between the vibrations at the hang-off segment along x and y directions.The 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 segments.Additionally,the incident current direction significantly affects the motion trajectory of the SWR which mainly includes the fusiform and rectangle shapes. 展开更多
关键词 steep wave riser(SWR) bidirectional vortex-induced vibration wake oscillator model time-domain finite element method(TDFEM)
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Vortex-induced Vibration of Elastically Connected Multiple Circular Cylinders in a Side-by-side Arrangement in Steady Flow
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作者 Kalyani Kaja Ming Zhao 《Hydro Science & Marine Engineering》 2020年第1期1-15,共15页
Vortex-induced vibration(VIV)of multiple circular cylinders elastically connected together in a side-by-side arrangement subject to steady flow is investigated numerically at a low Reynolds number of 150 and a mass ra... Vortex-induced vibration(VIV)of multiple circular cylinders elastically connected together in a side-by-side arrangement subject to steady flow is investigated numerically at a low Reynolds number of 150 and a mass ratio of 2.Simulations are conducted for two-,five-and ten-cylinder systems over a wide range of reduced velocities.The aim of the study is to identify the high-amplitude response range of the reduced velocity for the multiple degree of freedom vibration system and identify the difference between the responses of the single-and multiple-degree-of-freedom vibrations.Unlike the single cylinder case,distinct lock-in between the response frequency and any of the structural natural frequencies in a wide range of reduced velocity is not observed in the multiple-cylinder cases.Instead,the response frequency increases continuously with increasing reduced velocity.High response amplitudes are found when the response frequency is between the first and the highest modal frequencies.In a multiple-cylinder system,the single-mode response,where the vibration is dominated by one mode,can be only found in low reduced velocity range.In the single-mode branch,the dominance of a single mode shape in the response can be clearly identified except at the boundary reduced velocity between two modes.The maximum response amplitude occurs in the multiple-mode response and interaction between the vortices in the wake of the cylinders is strong when the response amplitudes are high. 展开更多
关键词 Vortex induced vibration Multiple cylinders numerical method
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A Numerical Modeling of the Vortex-induced Vibration of Cascade in Turbomachinery using Immersed Boundary Method 被引量:1
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作者 Guotun Hu Lin Du Guohua Zhong Xiaofeng Sun 《Journal of Thermal Science》 SCIE EI CAS CSCD 2011年第3期229-237,共9页
Based on the immersed boundary method,a fast simulation for solving unsteady,incompressible,viscous flow associated with the oscillating cascade is established on a quasi-three-dimensional coordinate system.The numeri... Based on the immersed boundary method,a fast simulation for solving unsteady,incompressible,viscous flow associated with the oscillating cascade is established on a quasi-three-dimensional coordinate system.The numerical method is applied to the simulation of the flow passing an oscillating circular cylinder which is forced to move in X direction under prescribed motions in water at rest at low Keulegan-Carpenter numbers.Then vor-tex-induced vibration of a cylinder with two degrees of freedom which oscillates in in-line direction and transverse direction is simulated using this method.The results are in good agreement with the previous research.Then the method is extended to the oscillating cascade simulation of making various comparisons.It is found that the IBPA(inter blade phase angle) will change as the time goes on,because of the non-uniformity of the flow in the circumferential direction,until the oscillating cascade goes to a stable situation.The reduced velocity and the number of blades are chosen to investigate the effects of them on IBPA.The results indicate that both the reduced velocity and the number of blades are the main factors which influence IBPA.It is worth noting that the coupling process is not necessary to generate any body-fitting grids,which makes it much faster in computational process for such a complicated fluid-structure interaction problem. 展开更多
关键词 TURBOMACHINERY IB method vortex-induced vibration oscillating cascade
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