The complex vibration directly affects the dynamic safety of drill string in ultra-deep wells and extra-deep wells.It is important to understand the dynamic characteristics of drill string to ensure the safety of dril...The complex vibration directly affects the dynamic safety of drill string in ultra-deep wells and extra-deep wells.It is important to understand the dynamic characteristics of drill string to ensure the safety of drill string.Due to the super slenderness ratio of drill string,strong nonlinearity implied in dynamic analysis and the complex load environment,dynamic simulation of drill string faces great challenges.At present,many simulation methods have been developed to analyze drill string dynamics,and node iteration method is one of them.The node iteration method has a unique advantage in dealing with the contact characteristics between drill string and borehole wall,but its drawback is that the calculation consumes a considerable amount of time.This paper presents a dynamic simulation method of drilling string in extra-deep well based on successive over-relaxation node iterative method(SOR node iteration method).Through theoretical analysis and numerical examples,the correctness and validity of this method were verified,and the dynamics characteristics of drill string in extra-deep wells were calculated and analyzed.The results demonstrate that,in contrast to the conventional node iteration method,the SOR node iteration method can increase the computational efficiency by 48.2%while achieving comparable results.And the whirl trajectory of the extra-deep well drill string is extremely complicated,the maximum rotational speed downhole is approximately twice the rotational speed on the ground.The dynamic torque increases rapidly at the position of the bottom stabilizer,and the lateral vibration in the middle and lower parts of drill string is relatively intense.展开更多
The feasibility of using a problem-dependent method to solve systems of second order ODEs is corroborated by an eigen-based theory and a methodology to develop such a numerical method is constructed.The key steps of t...The feasibility of using a problem-dependent method to solve systems of second order ODEs is corroborated by an eigen-based theory and a methodology to develop such a numerical method is constructed.The key steps of this methodology are to decouple a system of ODEs of second order into a set of uncoupled ODEs of second order;next,an eigen-dependent method is proposed to approximate the solution of each uncoupled ODE of second order.It is vital to transform all eigen-dependent methods to a problem-dependent method to bypass an Eigen analysis.The development of an eigen-dependent method plays a key role in this methodology so that slow eigenmodes can be accurately integrated while there is no instability or excessive amplitude growth in fast eigenmodes.This can explain why a problem-dependent method can simultaneously combine the explicitness of each step and A-stability.Consequently,huge computational efforts can be saved for solving nonlinear stiff problems.A new family of problem-dependent methods is developed in this work so that the feasibility of the proposed methodology can be affirmed.It has almost the same performance as that of the HHT-αmethod.However,it can save more than 99.5%of CPU demand in approximating a solution for a system of 1000 nonlinear second order ODEs.展开更多
In recent years,scholars around the world have shown increasing interest in elastic support structures,leading to significant progress in dynamic modeling techniques for pipeline systems.Although multiple analytical a...In recent years,scholars around the world have shown increasing interest in elastic support structures,leading to significant progress in dynamic modeling techniques for pipeline systems.Although multiple analytical approaches exist,engineers increasingly prioritize computationally efficient,precise low-order models for practical implementation.In order to address this need,this study develops an innovative nonlinear dynamic formulation for pipelines accounting for both foundation and boundary nonlinearities.The proposed solution methodology initiates with global mode extraction using the global mode technique,followed by a detailed implementation procedure.Model validation is conducted through a cantilever pipeline case study featuring nonlinear support conditions,where strong agreement between the proposed model's predictions and finiteelement benchmark solutions demonstrates its reliability.Subsequently,a comprehensive parametric study investigates the combined effects of foundation stiffness,boundary constraints,excitation intensity,and nonlinear interaction terms on the vibrational response of the cantilever pipe.This systematic approach yields critical insights for practical engineering designs and applications.展开更多
The distribution-free P-box process serves as an effective quantification model for timevarying uncertainties in dynamical systems when only imprecise probabilistic information is available.However,its application to ...The distribution-free P-box process serves as an effective quantification model for timevarying uncertainties in dynamical systems when only imprecise probabilistic information is available.However,its application to nonlinear systems remains limited due to excessive computation.This work develops an efficient method for propagating distribution-free P-box processes in nonlinear dynamics.First,using the Covariance Analysis Describing Equation Technique(CADET),the dynamic problems with P-box processes are transformed into interval Ordinary Differential Equations(ODEs).These equations provide the Mean-and-Covariance(MAC)bounds of the system responses in relation to the MAC bounds of P-box-process excitations.They also separate the previously coupled P-box analysis and nonlinear-dynamic simulations into two sequential steps,including the MAC bound analysis of excitations and the MAC bounds calculation of responses by solving the interval ODEs.Afterward,a Gaussian assumption of the CADET is extended to the P-box form,i.e.,the responses are approximate parametric Gaussian P-box processes.As a result,the probability bounds of the responses are approximated by using the solutions of the interval ODEs.Moreover,the Chebyshev method is introduced and modified to efficiently solve the interval ODEs.The proposed method is validated based on test cases,including a duffing oscillator,a vehicle ride,and an engineering black-box problem of launch vehicle trajectory.Compared to the reference solutions based on the Monte Carlo method,with relative errors of less than 3%,the proposed method requires less than 0.2% calculation time.The proposed method also possesses the ability to handle complex black-box problems.展开更多
In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated soils.Our approach incorporates the nodal integration technique into a gene...In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated soils.Our approach incorporates the nodal integration technique into a generalised Hellinger-Reissner(HR)variational principle,creating an implicit PFEM formulation.To mitigate the volumetric locking issue in low-order elements,we employ a node-based strain smoothing technique.By discretising field variables at the centre of smoothing cells,we achieve nodal integration over cells,eliminating the need for sophisticated mapping operations after re-meshing in the PFEM.We express the discretised governing equations as a min-max optimisation problem,which is further reformulated as a standard second-order cone programming(SOCP)problem.Stresses,pore water pressure,and displacements are simultaneously determined using the advanced primal-dual interior point method.Consequently,our numerical model offers improved accuracy for stresses and pore water pressure compared to the displacement-based PFEM formulation.Numerical experiments demonstrate that the N-PFEM efficiently captures both transient and long-term hydro-mechanical behaviour of saturated soils with high accuracy,obviating the need for stabilisation or regularisation techniques commonly employed in other nodal integration-based PFEM approaches.This work holds significant implications for the development of robust and accurate numerical tools for studying saturated soil dynamics.展开更多
This study explains the entropy process of natural convective heating in the nanofluid-saturated cavity in a heated fin andmagnetic field.The temperature is constant on the Y-shaped fin,insulating the topwall while th...This study explains the entropy process of natural convective heating in the nanofluid-saturated cavity in a heated fin andmagnetic field.The temperature is constant on the Y-shaped fin,insulating the topwall while the remaining walls remain cold.All walls are subject to impermeability and non-slip conditions.The mathematical modeling of the problem is demonstrated by the continuity,momentum,and energy equations incorporating the inclined magnetic field.For elucidating the flow characteristics Finite ElementMethod(FEM)is implemented using stable FE pair.A hybrid fine mesh is used for discretizing the domain.Velocity and thermal plots concerning parameters are drawn.In addition,a detailed discussion regarding generation energy by monitoring changes in magnetic,viscous,total,and thermal irreversibility is provided.In addition,line graphs are created for the u and v components of the velocity profile to predict the flow behavior.Current simulations assume the dimensionless representative of magnetic field Hartmann number Ha between 0 and 100 and a magnetic field inclination between 0 and 90 degrees.A constant 4% volume proportion of nanoparticles is employed throughout all scenarios.展开更多
Considerable efforts are being made to transition current lithium-ion and sodium-ion batteries towards the use of solid-state electrolytes.Computational methods,specifically nudged elastic band(NEB)and molecular dynam...Considerable efforts are being made to transition current lithium-ion and sodium-ion batteries towards the use of solid-state electrolytes.Computational methods,specifically nudged elastic band(NEB)and molecular dynamics(MD)methods,provide powerful tools for the design of solid-state electrolytes.The MD method is usually the choice for studying the materials involving complex multiple diffusion paths or having disordered structures.However,it relies on simulations at temperatures much higher than working temperature.This paper studies the reliability of the MD method using the system of Na diffusion in MgO as a benchmark.We carefully study the convergence behavior of the MD method and demonstrate that total effective simulation time of 12 ns can converge the calculated diffusion barrier to about 0.01 eV.The calculated diffusion barrier is 0.31 eV from both methods.The diffusion coefficients at room temperature are 4.3×10^(-9) cm^(2)⋅s^(−1) and 2.2×10^(-9) cm^(2)⋅s^(−1),respectively,from the NEB and MD methods.Our results justify the reliability of the MD method,even though high temperature simulations have to be employed to overcome the limitation on simulation time.展开更多
In this paper,we construct a high-order discontinuous Galerkin(DG)method which can preserve the positivity of the density and the pressure for the viscous and resistive magnetohydrodynamics(VRMHD).To control the diver...In this paper,we construct a high-order discontinuous Galerkin(DG)method which can preserve the positivity of the density and the pressure for the viscous and resistive magnetohydrodynamics(VRMHD).To control the divergence error in the magnetic field,both the local divergence-free basis and the Godunov source term would be employed for the multi-dimensional VRMHD.Rigorous theoretical analyses are presented for one-dimensional and multi-dimensional DG schemes,respectively,showing that the scheme can maintain the positivity-preserving(PP)property under some CFL conditions when combined with the strong-stability-preserving time discretization.Then,general frameworks are established to construct the PP limiter for arbitrary order of accuracy DG schemes.Numerical tests demonstrate the effectiveness of the proposed schemes.展开更多
Viscoelastic flows play an important role in numerous engineering fields,and the multiscale algorithms for simulating viscoelastic flows have received significant attention in order to deepen our understanding of the ...Viscoelastic flows play an important role in numerous engineering fields,and the multiscale algorithms for simulating viscoelastic flows have received significant attention in order to deepen our understanding of the nonlinear dynamic behaviors of viscoelastic fluids.However,traditional grid-based multiscale methods are confined to simple viscoelastic flows with short relaxation time,and there is a lack of uniform multiscale scheme available for coupling different solvers in the simulations of viscoelastic fluids.In this paper,a universal multiscale method coupling an improved smoothed particle hydrodynamics(SPH)and multiscale universal interface(MUI)library is presented for viscoelastic flows.The proposed multiscale method builds on an improved SPH method and leverages the MUI library to facilitate the exchange of information among different solvers in the overlapping domain.We test the capability and flexibility of the presented multiscale method to deal with complex viscoelastic flows by solving different multiscale problems of viscoelastic flows.In the first example,the simulation of a viscoelastic Poiseuille flow is carried out by two coupled improved SPH methods with different spatial resolutions.The effects of exchanging different physical quantities on the numerical results in both the upper and lower domains are also investigated as well as the absolute errors in the overlapping domain.In the second example,the complex Wannier flow with different Weissenberg numbers is further simulated by two improved SPH methods and coupling the improved SPH method and the dissipative particle dynamics(DPD)method.The numerical results show that the physical quantities for viscoelastic flows obtained by the presented multiscale method are in consistence with those obtained by a single solver in the overlapping domain.Moreover,transferring different physical quantities has an important effect on the numerical results.展开更多
The high-speed winding spindle employs a flexible support system incorporating rubber O-rings.By precisely configuring the structural parameters and the number of the O-rings,the spindle can stably surpass its critica...The high-speed winding spindle employs a flexible support system incorporating rubber O-rings.By precisely configuring the structural parameters and the number of the O-rings,the spindle can stably surpass its critical speed points and maintain operational stability across the entire working speed range.However,the support stiffness and damping of rubber O-rings exhibit significant nonlinear frequency dependence.Conventional experimental methods for deriving equivalent stiffness and damping,based on the principle of the forced non-resonance method,require fabricating custom setups for each O-ring specification and conducting vibration tests at varying frequencies,resulting in low efficiency and high costs.This study proposes a hybrid simulation-experimental method for dynamic parameter identification.Firstly,the frequency-dependent dynamic parameters of a specific O-ring support system are experimentally obtained.Subsequently,a corresponding parametric finite element model is established to simulate and solve the equivalent elastic modulus and equivalent stiffness-damping coefficient of this O-ring support system.Ultimately,after iterative simulation,the simulated and experimental results achieve a 99.7%agreement.The parametric finite element model developed herein can directly simulate and inversely estimate frequency-dependent dynamic parameters for O-rings of different specifications but identical elastic modulus.展开更多
This study presents a numerical analysis of the steady-state solution for transient magnetohydrodynamic(MHD)dissipative and radiative fluid flow,incorporating an inducedmagnetic field(IMF)and considering a relatively ...This study presents a numerical analysis of the steady-state solution for transient magnetohydrodynamic(MHD)dissipative and radiative fluid flow,incorporating an inducedmagnetic field(IMF)and considering a relatively high concentration of foreign mass(accounting for Soret and Dufour effects)over a vertically oriented semi-infinite plate.The governing equations were normalized using boundary layer(BL)approximations.The resulting nonlinear system of partial differential equations(PDEs)was discretized and solved using an efficient explicit finite difference method(FDM).Numerical simulations were conducted using MATLAB R2015a,and the developed numerical code was verified through comparison with another code written in FORTRAN 6.6a.To ensure the reliability of the results,both mesh refinement and steady-state time validation tests were performed.Furthermore,a comparison with existing published studies was made to confirm the accuracy of the findings.The dimensionless equations revealed the impacts of several key parameters.The IMF initially intensifies near the plate before gradually diminishing as the magnetic parameter increases.For the range 0≤y≤1.8(where y is the horizontal direction),the IMF decreases with a rise in the magnetic Prandtl number;however,for 1.8≤y≤7(approximately),the magnetic field begins to increase.Beyond this,the profile of the magnetic field becomes somewhat irregular through the remaining part of the BL.展开更多
This study employs two-dimensional axisymmetric relativistic magnetohydrodynamic simulations to investigate the evolution of supernova remnant(SNR) and pulsar wind nebula(PWN) composite systems in two distinct interst...This study employs two-dimensional axisymmetric relativistic magnetohydrodynamic simulations to investigate the evolution of supernova remnant(SNR) and pulsar wind nebula(PWN) composite systems in two distinct interstellar medium(ISM) configurations: a uniform density distribution and a medium with a sharp density discontinuity. Compared to the uniform density distribution, the ISM with this density discontinuity better reflects the actual conditions and explains the overall morphological characteristics of specific types of SNR-PWN composite systems. These systems exhibit asymmetries, such as an SNR shell with differing radii or an inner PWN located nearer to the shell on one side. The simulation results suggest that the density discontinuity in the ISM is a contributing factor to both the shell asymmetry and the PWN displacement. Specifically, this density variation directly causes the inconsistency in the forward shock speeds of the SNR between high and low density regions, resulting in discrepancies in the shell layer radii. Furthermore, the asymmetric morphology of the PWN and its positional offset emerge through interactions with the reverse shock. The PWN tends to shift toward the SNR shell on one side. The greater the density jump in the background field, the more pronounced the shell radius differences and PWN offset become.展开更多
Currently,the cranes used at sea do not have enough flexibility,efficiency,and safety.Thus,this study proposed a floating multirobot coordinated towing system to meet the demands for offshore towing.Because of the fle...Currently,the cranes used at sea do not have enough flexibility,efficiency,and safety.Thus,this study proposed a floating multirobot coordinated towing system to meet the demands for offshore towing.Because of the flexibility of rope-driven robots,the one-way pulling characteristics of the rope,and the floating characteristics of the base,towing robots are easily overturned.First,the spatial configuration of the towing system was established according to the towing task,and the kinematic model of the towing system was established using the coordinate transformation.Then,the dynamic model of the towing system was established according to the rigid-body dynamics and hydrodynamic theory.Finally,the stability of the towing system was analyzed using the stability cone method.The simulation experiments provide a reference for the practical application of the floating multirobot coordinated towing system,which can improve the stability of towing systems by changing the configuration of the towing robot.展开更多
Gas turbine rotors are complex dynamic systems with high-dimensional,discrete,and multi-source nonlinear coupling characteristics.Significant amounts of resources and time are spent during the process of solving dynam...Gas turbine rotors are complex dynamic systems with high-dimensional,discrete,and multi-source nonlinear coupling characteristics.Significant amounts of resources and time are spent during the process of solving dynamic characteristics.Therefore,it is necessary to design a lowdimensional model that can well reflect the dynamic characteristics of high-dimensional system.To build such a low-dimensional model,this study developed a dimensionality reduction method considering global order energy distribution by modifying the proper orthogonal decomposition theory.First,sensitivity analysis of key dimensionality reduction parameters to the energy distribution was conducted.Then a high-dimensional rotor-bearing system considering the nonlinear stiffness and oil film force was reduced,and the accuracy and the reusability of the low-dimensional model under different operating conditions were examined.Finally,the response results of a multi-disk rotor-bearing test bench were reduced using the proposed method,and spectrum results were then compared experimentally.Numerical and experimental results demonstrate that,during the dimensionality reduction process,the solution period of dynamic response results has the most significant influence on the accuracy of energy preservation.The transient signal in the transformation matrix mainly affects the high-order energy distribution of the rotor system.The larger the proportion of steady-state signals is,the closer the energy tends to accumulate towards lower orders.The low-dimensional rotor model accurately reflects the frequency response characteristics of the original high-dimensional system with an accuracy of up to 98%.The proposed dimensionality reduction method exhibits significant application potential in the dynamic analysis of highdimensional systems coupled with strong nonlinearities under variable operating conditions.展开更多
The microstructure and related property evolution induced by dynamic recrystallization(DRX)and static recrystallization(SRX)in thermo-mechanical process are two critical factors for the metal forming.The DRX and SRX a...The microstructure and related property evolution induced by dynamic recrystallization(DRX)and static recrystallization(SRX)in thermo-mechanical process are two critical factors for the metal forming.The DRX and SRX are determined by the grain level deformation and sequentially coupled.In order to fully capture the microstructure and mechanical property evolution,a crystal plasticity finite element based modelling method for DRX and SRX is proposed in the current work.The grain level deformation is calculated with crystal plasticity which is coupled with the recrystallization model straightforwardly,and both the grain deformation and microstructure evolution are updated simultaneously.The proposed method is validated with discontinuous DRX experiments and the effects of initial deformation conditions are well-captured.Two controversial mechanisms for recrystallization microstructure evolution,i.e.oriented nucleation and growth selection,are discussed in the current framework with the advantages of accurate grain level deformation and interaction predictions.Furthermore,the sequentially coupled DRX and SRX are modelled seamlessly in the current work which provides a critical method for fully integrated thermo-mechanical processes analysis.展开更多
The investigation of leachate-contaminated clay(LCC)is essential for landfill engineering assessment and achievement of sustainable development goals.Several static and dynamic laboratory tests,including unconfined co...The investigation of leachate-contaminated clay(LCC)is essential for landfill engineering assessment and achievement of sustainable development goals.Several static and dynamic laboratory tests,including unconfined compressive strength(UCS),California bearing ratio(CBR),and cyclic simple shear,are conducted.Cyclic simple shear experiments on LCCs were performed to evaluate the damping and shear modulus.The investigated factors are vertical load(VL),leachate content(LC),frequency(F),and shear strain(ShS)for LCC.Forensic-based investigation optimization(FBIO)and equilibrium optimizer algorithm(EOA)were utilized in addition to multiple types of ensemble models,including adaptive boosting(ADB),gradient boosting regression tree(GBRT),extreme gradient boosting(XGB) and random forest(RF).The comparison of the methods showed that GBRT-FBIO and XGB-EOA models outperformed other models for shear modulus and damping of LCC.The p-value less than 0.0001 shows the significance of the used models in the response surface methodology(RSM)method.展开更多
An advanced Actuator Surface Method(ASM)coupled with Computational Fluid Dynamics(CFD)is developed and applied to the complex unsteady aerodynamic simulation of helicopter.By introducing an improved three-dimensional ...An advanced Actuator Surface Method(ASM)coupled with Computational Fluid Dynamics(CFD)is developed and applied to the complex unsteady aerodynamic simulation of helicopter.By introducing an improved three-dimensional anisotropic Gaussian kernel,this method effectively addresses the severe aerodynamic load fluctuations commonly associated with traditional Virtual Blade Method(VBM)due to turbulent flow around blade elements.To manage the issues of regional shape and grid cell quantity variations caused by virtual blade sweeping,a universal hybrid grid generation strategy is established without body-fitted and disk interpolation grids,which enhances the computational stability at both blade elements and blade edges.Aerodynamic numerical simulations of helicopter are performed using this method,focusing on rotor/fuselage interaction dominated by rotor wake motion and fuselage blockage effects,Blade-Vortex Interaction(BVI)induced by tip vortices,and maneuvering flights involving collective pitch ramp increases.The results indicate that the advanced ASM demonstrates reliability and robustness in the simulation of complex unsteady flow fields around helicopter.Under similar computational accuracy,the advanced ASM improves computational efficiency by nearly 40 times compared to the oversetgrid-based full Blade-Resolved(B-R)method,and by 6 times compared to the VBM.It shows significant advantages when applied to complex full-aircraft interaction and maneuvering flight conditions that require substantial computational resources.展开更多
In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin proj...In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability.展开更多
This paper presents a framework for constructing surrogate models for sensitivity analysis of structural dynamics behavior.Physical models involving deformation,such as collisions,vibrations,and penetration,are devel-...This paper presents a framework for constructing surrogate models for sensitivity analysis of structural dynamics behavior.Physical models involving deformation,such as collisions,vibrations,and penetration,are devel-oped using the material point method.To reduce the computational cost of Monte Carlo simulations,response surface models are created as surrogate models for the material point system to approximate its dynamic behavior.An adaptive randomized greedy algorithm is employed to construct a sparse polynomial chaos expansion model with a fixed order,effectively balancing the accuracy and computational efficiency of the surrogate model.Based on the sparse polynomial chaos expansion,sensitivity analysis is conducted using the global finite difference and Sobol methods.Several examples of structural dynamics are provided to demonstrate the effectiveness of the proposed method in addressing structural dynamics problems.展开更多
Underwater launch is a transient vibration process under the impact load.The hydrodynamic calculation is an important part of equipment research.In this paper,firstly,combining the theory of the Euler-Bernoulli beam a...Underwater launch is a transient vibration process under the impact load.The hydrodynamic calculation is an important part of equipment research.In this paper,firstly,combining the theory of the Euler-Bernoulli beam and the potential flow,the transfer equation of the Euler-Bernoulli beam considering the hydroelastic effect is derived,which expands the application scope of the transfer matrix.The correctness of the transfer matrix for the beam with hydroelastic behaviors is verified by comparison with the results of the finite element analysis.Then the dynamics model of the underwater launch system is established based on the multibody system transfer matrix method,and the beam with hydroelastic behaviors is employed as the external vehicle.Subsequently,the overall transfer and dynamic equation are derived,resulting in the solution of the wet natural frequency and the dynamic response under the impact load.The comparison with experimental data validates the dynamics model and simulation results and ensures its reliability in practical applications.The dynamic of the system demonstrates that the launching interval and adjacent tube effect will exert an influence on the subsequent emission.This research provides a fast and efficient method for the dynamic calculation of the underwater launch system.展开更多
基金supported by the National Natural Science Foundation of China(52174003,52374008).
文摘The complex vibration directly affects the dynamic safety of drill string in ultra-deep wells and extra-deep wells.It is important to understand the dynamic characteristics of drill string to ensure the safety of drill string.Due to the super slenderness ratio of drill string,strong nonlinearity implied in dynamic analysis and the complex load environment,dynamic simulation of drill string faces great challenges.At present,many simulation methods have been developed to analyze drill string dynamics,and node iteration method is one of them.The node iteration method has a unique advantage in dealing with the contact characteristics between drill string and borehole wall,but its drawback is that the calculation consumes a considerable amount of time.This paper presents a dynamic simulation method of drilling string in extra-deep well based on successive over-relaxation node iterative method(SOR node iteration method).Through theoretical analysis and numerical examples,the correctness and validity of this method were verified,and the dynamics characteristics of drill string in extra-deep wells were calculated and analyzed.The results demonstrate that,in contrast to the conventional node iteration method,the SOR node iteration method can increase the computational efficiency by 48.2%while achieving comparable results.And the whirl trajectory of the extra-deep well drill string is extremely complicated,the maximum rotational speed downhole is approximately twice the rotational speed on the ground.The dynamic torque increases rapidly at the position of the bottom stabilizer,and the lateral vibration in the middle and lower parts of drill string is relatively intense.
文摘The feasibility of using a problem-dependent method to solve systems of second order ODEs is corroborated by an eigen-based theory and a methodology to develop such a numerical method is constructed.The key steps of this methodology are to decouple a system of ODEs of second order into a set of uncoupled ODEs of second order;next,an eigen-dependent method is proposed to approximate the solution of each uncoupled ODE of second order.It is vital to transform all eigen-dependent methods to a problem-dependent method to bypass an Eigen analysis.The development of an eigen-dependent method plays a key role in this methodology so that slow eigenmodes can be accurately integrated while there is no instability or excessive amplitude growth in fast eigenmodes.This can explain why a problem-dependent method can simultaneously combine the explicitness of each step and A-stability.Consequently,huge computational efforts can be saved for solving nonlinear stiff problems.A new family of problem-dependent methods is developed in this work so that the feasibility of the proposed methodology can be affirmed.It has almost the same performance as that of the HHT-αmethod.However,it can save more than 99.5%of CPU demand in approximating a solution for a system of 1000 nonlinear second order ODEs.
基金supported by the National Natural Science Foundation of China(Nos.52401342 and 12572025)the Fundamental Research Funds for the Central Universities of China(Nos.D5000240076 and G2025KY05171)+1 种基金the Natural Science Basic Research Program of Shaanxi Province(No.2025JCYBMS-026)the Basic Research Programs of Taicang(No.TC2024JC36)。
文摘In recent years,scholars around the world have shown increasing interest in elastic support structures,leading to significant progress in dynamic modeling techniques for pipeline systems.Although multiple analytical approaches exist,engineers increasingly prioritize computationally efficient,precise low-order models for practical implementation.In order to address this need,this study develops an innovative nonlinear dynamic formulation for pipelines accounting for both foundation and boundary nonlinearities.The proposed solution methodology initiates with global mode extraction using the global mode technique,followed by a detailed implementation procedure.Model validation is conducted through a cantilever pipeline case study featuring nonlinear support conditions,where strong agreement between the proposed model's predictions and finiteelement benchmark solutions demonstrates its reliability.Subsequently,a comprehensive parametric study investigates the combined effects of foundation stiffness,boundary constraints,excitation intensity,and nonlinear interaction terms on the vibrational response of the cantilever pipe.This systematic approach yields critical insights for practical engineering designs and applications.
基金supported by the major advanced research project of Civil Aerospace from State Administration of Science,Technology and Industry of China.
文摘The distribution-free P-box process serves as an effective quantification model for timevarying uncertainties in dynamical systems when only imprecise probabilistic information is available.However,its application to nonlinear systems remains limited due to excessive computation.This work develops an efficient method for propagating distribution-free P-box processes in nonlinear dynamics.First,using the Covariance Analysis Describing Equation Technique(CADET),the dynamic problems with P-box processes are transformed into interval Ordinary Differential Equations(ODEs).These equations provide the Mean-and-Covariance(MAC)bounds of the system responses in relation to the MAC bounds of P-box-process excitations.They also separate the previously coupled P-box analysis and nonlinear-dynamic simulations into two sequential steps,including the MAC bound analysis of excitations and the MAC bounds calculation of responses by solving the interval ODEs.Afterward,a Gaussian assumption of the CADET is extended to the P-box form,i.e.,the responses are approximate parametric Gaussian P-box processes.As a result,the probability bounds of the responses are approximated by using the solutions of the interval ODEs.Moreover,the Chebyshev method is introduced and modified to efficiently solve the interval ODEs.The proposed method is validated based on test cases,including a duffing oscillator,a vehicle ride,and an engineering black-box problem of launch vehicle trajectory.Compared to the reference solutions based on the Monte Carlo method,with relative errors of less than 3%,the proposed method requires less than 0.2% calculation time.The proposed method also possesses the ability to handle complex black-box problems.
基金supported by the Swiss National Science Foundation(Grant No.189882)the National Natural Science Foundation of China(Grant No.41961134032)support provided by the New Investigator Award grant from the UK Engineering and Physical Sciences Research Council(Grant No.EP/V012169/1).
文摘In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated soils.Our approach incorporates the nodal integration technique into a generalised Hellinger-Reissner(HR)variational principle,creating an implicit PFEM formulation.To mitigate the volumetric locking issue in low-order elements,we employ a node-based strain smoothing technique.By discretising field variables at the centre of smoothing cells,we achieve nodal integration over cells,eliminating the need for sophisticated mapping operations after re-meshing in the PFEM.We express the discretised governing equations as a min-max optimisation problem,which is further reformulated as a standard second-order cone programming(SOCP)problem.Stresses,pore water pressure,and displacements are simultaneously determined using the advanced primal-dual interior point method.Consequently,our numerical model offers improved accuracy for stresses and pore water pressure compared to the displacement-based PFEM formulation.Numerical experiments demonstrate that the N-PFEM efficiently captures both transient and long-term hydro-mechanical behaviour of saturated soils with high accuracy,obviating the need for stabilisation or regularisation techniques commonly employed in other nodal integration-based PFEM approaches.This work holds significant implications for the development of robust and accurate numerical tools for studying saturated soil dynamics.
文摘This study explains the entropy process of natural convective heating in the nanofluid-saturated cavity in a heated fin andmagnetic field.The temperature is constant on the Y-shaped fin,insulating the topwall while the remaining walls remain cold.All walls are subject to impermeability and non-slip conditions.The mathematical modeling of the problem is demonstrated by the continuity,momentum,and energy equations incorporating the inclined magnetic field.For elucidating the flow characteristics Finite ElementMethod(FEM)is implemented using stable FE pair.A hybrid fine mesh is used for discretizing the domain.Velocity and thermal plots concerning parameters are drawn.In addition,a detailed discussion regarding generation energy by monitoring changes in magnetic,viscous,total,and thermal irreversibility is provided.In addition,line graphs are created for the u and v components of the velocity profile to predict the flow behavior.Current simulations assume the dimensionless representative of magnetic field Hartmann number Ha between 0 and 100 and a magnetic field inclination between 0 and 90 degrees.A constant 4% volume proportion of nanoparticles is employed throughout all scenarios.
基金supported by the National Natural Science Foundation of China (Grant Nos.12164019,11991060,12088101,and U1930402)the Natural Science Foundation of Jiangxi Province of China (Grant No.20212BAB201017).
文摘Considerable efforts are being made to transition current lithium-ion and sodium-ion batteries towards the use of solid-state electrolytes.Computational methods,specifically nudged elastic band(NEB)and molecular dynamics(MD)methods,provide powerful tools for the design of solid-state electrolytes.The MD method is usually the choice for studying the materials involving complex multiple diffusion paths or having disordered structures.However,it relies on simulations at temperatures much higher than working temperature.This paper studies the reliability of the MD method using the system of Na diffusion in MgO as a benchmark.We carefully study the convergence behavior of the MD method and demonstrate that total effective simulation time of 12 ns can converge the calculated diffusion barrier to about 0.01 eV.The calculated diffusion barrier is 0.31 eV from both methods.The diffusion coefficients at room temperature are 4.3×10^(-9) cm^(2)⋅s^(−1) and 2.2×10^(-9) cm^(2)⋅s^(−1),respectively,from the NEB and MD methods.Our results justify the reliability of the MD method,even though high temperature simulations have to be employed to overcome the limitation on simulation time.
基金supported by the NSFC Grant 11901555,12271499the Cyrus Tang Foundationsupported by the NSFC Grant 11871448 and 12126604.
文摘In this paper,we construct a high-order discontinuous Galerkin(DG)method which can preserve the positivity of the density and the pressure for the viscous and resistive magnetohydrodynamics(VRMHD).To control the divergence error in the magnetic field,both the local divergence-free basis and the Godunov source term would be employed for the multi-dimensional VRMHD.Rigorous theoretical analyses are presented for one-dimensional and multi-dimensional DG schemes,respectively,showing that the scheme can maintain the positivity-preserving(PP)property under some CFL conditions when combined with the strong-stability-preserving time discretization.Then,general frameworks are established to construct the PP limiter for arbitrary order of accuracy DG schemes.Numerical tests demonstrate the effectiveness of the proposed schemes.
基金Project supported by the National Natural Science Foundation of China(No.52109068)the Water Conservancy Technology Project of Jiangsu Province of China(No.2022060)。
文摘Viscoelastic flows play an important role in numerous engineering fields,and the multiscale algorithms for simulating viscoelastic flows have received significant attention in order to deepen our understanding of the nonlinear dynamic behaviors of viscoelastic fluids.However,traditional grid-based multiscale methods are confined to simple viscoelastic flows with short relaxation time,and there is a lack of uniform multiscale scheme available for coupling different solvers in the simulations of viscoelastic fluids.In this paper,a universal multiscale method coupling an improved smoothed particle hydrodynamics(SPH)and multiscale universal interface(MUI)library is presented for viscoelastic flows.The proposed multiscale method builds on an improved SPH method and leverages the MUI library to facilitate the exchange of information among different solvers in the overlapping domain.We test the capability and flexibility of the presented multiscale method to deal with complex viscoelastic flows by solving different multiscale problems of viscoelastic flows.In the first example,the simulation of a viscoelastic Poiseuille flow is carried out by two coupled improved SPH methods with different spatial resolutions.The effects of exchanging different physical quantities on the numerical results in both the upper and lower domains are also investigated as well as the absolute errors in the overlapping domain.In the second example,the complex Wannier flow with different Weissenberg numbers is further simulated by two improved SPH methods and coupling the improved SPH method and the dissipative particle dynamics(DPD)method.The numerical results show that the physical quantities for viscoelastic flows obtained by the presented multiscale method are in consistence with those obtained by a single solver in the overlapping domain.Moreover,transferring different physical quantities has an important effect on the numerical results.
基金National Key R&D Program of China(No.2017YFB1304000)Fundamental Research Funds for the Central Universities,China(No.2232023G-05-1)。
文摘The high-speed winding spindle employs a flexible support system incorporating rubber O-rings.By precisely configuring the structural parameters and the number of the O-rings,the spindle can stably surpass its critical speed points and maintain operational stability across the entire working speed range.However,the support stiffness and damping of rubber O-rings exhibit significant nonlinear frequency dependence.Conventional experimental methods for deriving equivalent stiffness and damping,based on the principle of the forced non-resonance method,require fabricating custom setups for each O-ring specification and conducting vibration tests at varying frequencies,resulting in low efficiency and high costs.This study proposes a hybrid simulation-experimental method for dynamic parameter identification.Firstly,the frequency-dependent dynamic parameters of a specific O-ring support system are experimentally obtained.Subsequently,a corresponding parametric finite element model is established to simulate and solve the equivalent elastic modulus and equivalent stiffness-damping coefficient of this O-ring support system.Ultimately,after iterative simulation,the simulated and experimental results achieve a 99.7%agreement.The parametric finite element model developed herein can directly simulate and inversely estimate frequency-dependent dynamic parameters for O-rings of different specifications but identical elastic modulus.
基金supported by the NST Fellowship under the Ministry of Science and Technology,Government of the People’s Republic of Bangladesh(Session:2019–2020,merit number:334,serial number:714,physical science).
文摘This study presents a numerical analysis of the steady-state solution for transient magnetohydrodynamic(MHD)dissipative and radiative fluid flow,incorporating an inducedmagnetic field(IMF)and considering a relatively high concentration of foreign mass(accounting for Soret and Dufour effects)over a vertically oriented semi-infinite plate.The governing equations were normalized using boundary layer(BL)approximations.The resulting nonlinear system of partial differential equations(PDEs)was discretized and solved using an efficient explicit finite difference method(FDM).Numerical simulations were conducted using MATLAB R2015a,and the developed numerical code was verified through comparison with another code written in FORTRAN 6.6a.To ensure the reliability of the results,both mesh refinement and steady-state time validation tests were performed.Furthermore,a comparison with existing published studies was made to confirm the accuracy of the findings.The dimensionless equations revealed the impacts of several key parameters.The IMF initially intensifies near the plate before gradually diminishing as the magnetic parameter increases.For the range 0≤y≤1.8(where y is the horizontal direction),the IMF decreases with a rise in the magnetic Prandtl number;however,for 1.8≤y≤7(approximately),the magnetic field begins to increase.Beyond this,the profile of the magnetic field becomes somewhat irregular through the remaining part of the BL.
基金supported by the National Natural Science Foundation of China(NSFC,grants No.12393852)the Yunnan Fundamental Research Projects(grant No.202501AS070068)the Program of Graduate Research and Innovation Fund Project of Yunnan University(KC-24249493).
文摘This study employs two-dimensional axisymmetric relativistic magnetohydrodynamic simulations to investigate the evolution of supernova remnant(SNR) and pulsar wind nebula(PWN) composite systems in two distinct interstellar medium(ISM) configurations: a uniform density distribution and a medium with a sharp density discontinuity. Compared to the uniform density distribution, the ISM with this density discontinuity better reflects the actual conditions and explains the overall morphological characteristics of specific types of SNR-PWN composite systems. These systems exhibit asymmetries, such as an SNR shell with differing radii or an inner PWN located nearer to the shell on one side. The simulation results suggest that the density discontinuity in the ISM is a contributing factor to both the shell asymmetry and the PWN displacement. Specifically, this density variation directly causes the inconsistency in the forward shock speeds of the SNR between high and low density regions, resulting in discrepancies in the shell layer radii. Furthermore, the asymmetric morphology of the PWN and its positional offset emerge through interactions with the reverse shock. The PWN tends to shift toward the SNR shell on one side. The greater the density jump in the background field, the more pronounced the shell radius differences and PWN offset become.
基金Supported by the National Natural Science Foundation of China under Grant No.51965032the Natural Science Foundation of Gansu Province of China under Grant No.22JR5RA319+2 种基金the Excellent Doctoral Student Foundation of Gansu Province of China under Grant No.23JRRA842the Sichuan Province Engineering Technology Research Center of General Aircraft Maintenance under Grant No.GAMRC2023YB05the Key Research and Development Project of Lanzhou Jiaotong University under Grant No.LZJTUZDYF2302.
文摘Currently,the cranes used at sea do not have enough flexibility,efficiency,and safety.Thus,this study proposed a floating multirobot coordinated towing system to meet the demands for offshore towing.Because of the flexibility of rope-driven robots,the one-way pulling characteristics of the rope,and the floating characteristics of the base,towing robots are easily overturned.First,the spatial configuration of the towing system was established according to the towing task,and the kinematic model of the towing system was established using the coordinate transformation.Then,the dynamic model of the towing system was established according to the rigid-body dynamics and hydrodynamic theory.Finally,the stability of the towing system was analyzed using the stability cone method.The simulation experiments provide a reference for the practical application of the floating multirobot coordinated towing system,which can improve the stability of towing systems by changing the configuration of the towing robot.
基金supported by the China Postdoctoral Science Foundation(No.2024M764171)the Postdoctoral Research Start-up Funds,China(No.AUGA5710027424)+1 种基金the National Natural Science Foundation of China(No.U2341237)the Development and construction funds for the School of Mechatronics Engineering of HIT,China(No.CBQQ8880103624)。
文摘Gas turbine rotors are complex dynamic systems with high-dimensional,discrete,and multi-source nonlinear coupling characteristics.Significant amounts of resources and time are spent during the process of solving dynamic characteristics.Therefore,it is necessary to design a lowdimensional model that can well reflect the dynamic characteristics of high-dimensional system.To build such a low-dimensional model,this study developed a dimensionality reduction method considering global order energy distribution by modifying the proper orthogonal decomposition theory.First,sensitivity analysis of key dimensionality reduction parameters to the energy distribution was conducted.Then a high-dimensional rotor-bearing system considering the nonlinear stiffness and oil film force was reduced,and the accuracy and the reusability of the low-dimensional model under different operating conditions were examined.Finally,the response results of a multi-disk rotor-bearing test bench were reduced using the proposed method,and spectrum results were then compared experimentally.Numerical and experimental results demonstrate that,during the dimensionality reduction process,the solution period of dynamic response results has the most significant influence on the accuracy of energy preservation.The transient signal in the transformation matrix mainly affects the high-order energy distribution of the rotor system.The larger the proportion of steady-state signals is,the closer the energy tends to accumulate towards lower orders.The low-dimensional rotor model accurately reflects the frequency response characteristics of the original high-dimensional system with an accuracy of up to 98%.The proposed dimensionality reduction method exhibits significant application potential in the dynamic analysis of highdimensional systems coupled with strong nonlinearities under variable operating conditions.
基金supported by the National Natural Science Foundation of China(Nos.52105384 and U2141215).
文摘The microstructure and related property evolution induced by dynamic recrystallization(DRX)and static recrystallization(SRX)in thermo-mechanical process are two critical factors for the metal forming.The DRX and SRX are determined by the grain level deformation and sequentially coupled.In order to fully capture the microstructure and mechanical property evolution,a crystal plasticity finite element based modelling method for DRX and SRX is proposed in the current work.The grain level deformation is calculated with crystal plasticity which is coupled with the recrystallization model straightforwardly,and both the grain deformation and microstructure evolution are updated simultaneously.The proposed method is validated with discontinuous DRX experiments and the effects of initial deformation conditions are well-captured.Two controversial mechanisms for recrystallization microstructure evolution,i.e.oriented nucleation and growth selection,are discussed in the current framework with the advantages of accurate grain level deformation and interaction predictions.Furthermore,the sequentially coupled DRX and SRX are modelled seamlessly in the current work which provides a critical method for fully integrated thermo-mechanical processes analysis.
文摘The investigation of leachate-contaminated clay(LCC)is essential for landfill engineering assessment and achievement of sustainable development goals.Several static and dynamic laboratory tests,including unconfined compressive strength(UCS),California bearing ratio(CBR),and cyclic simple shear,are conducted.Cyclic simple shear experiments on LCCs were performed to evaluate the damping and shear modulus.The investigated factors are vertical load(VL),leachate content(LC),frequency(F),and shear strain(ShS)for LCC.Forensic-based investigation optimization(FBIO)and equilibrium optimizer algorithm(EOA)were utilized in addition to multiple types of ensemble models,including adaptive boosting(ADB),gradient boosting regression tree(GBRT),extreme gradient boosting(XGB) and random forest(RF).The comparison of the methods showed that GBRT-FBIO and XGB-EOA models outperformed other models for shear modulus and damping of LCC.The p-value less than 0.0001 shows the significance of the used models in the response surface methodology(RSM)method.
基金co-supported by the Foundation of the State Key Laboratory of Aerodynamics(No.RAL202203)the National Key Laboratory Foundation(No.6142202202)the China Postdoctoral Science Foundation(No.2024M754133)。
文摘An advanced Actuator Surface Method(ASM)coupled with Computational Fluid Dynamics(CFD)is developed and applied to the complex unsteady aerodynamic simulation of helicopter.By introducing an improved three-dimensional anisotropic Gaussian kernel,this method effectively addresses the severe aerodynamic load fluctuations commonly associated with traditional Virtual Blade Method(VBM)due to turbulent flow around blade elements.To manage the issues of regional shape and grid cell quantity variations caused by virtual blade sweeping,a universal hybrid grid generation strategy is established without body-fitted and disk interpolation grids,which enhances the computational stability at both blade elements and blade edges.Aerodynamic numerical simulations of helicopter are performed using this method,focusing on rotor/fuselage interaction dominated by rotor wake motion and fuselage blockage effects,Blade-Vortex Interaction(BVI)induced by tip vortices,and maneuvering flights involving collective pitch ramp increases.The results indicate that the advanced ASM demonstrates reliability and robustness in the simulation of complex unsteady flow fields around helicopter.Under similar computational accuracy,the advanced ASM improves computational efficiency by nearly 40 times compared to the oversetgrid-based full Blade-Resolved(B-R)method,and by 6 times compared to the VBM.It shows significant advantages when applied to complex full-aircraft interaction and maneuvering flight conditions that require substantial computational resources.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2141254 and U23B6009)。
文摘In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability.
基金support from the National Natural Science Foundation of China(Grant Nos.52174123&52274222).
文摘This paper presents a framework for constructing surrogate models for sensitivity analysis of structural dynamics behavior.Physical models involving deformation,such as collisions,vibrations,and penetration,are devel-oped using the material point method.To reduce the computational cost of Monte Carlo simulations,response surface models are created as surrogate models for the material point system to approximate its dynamic behavior.An adaptive randomized greedy algorithm is employed to construct a sparse polynomial chaos expansion model with a fixed order,effectively balancing the accuracy and computational efficiency of the surrogate model.Based on the sparse polynomial chaos expansion,sensitivity analysis is conducted using the global finite difference and Sobol methods.Several examples of structural dynamics are provided to demonstrate the effectiveness of the proposed method in addressing structural dynamics problems.
基金supported by the National Natural Science Foundation of China(Grant No.92266201).
文摘Underwater launch is a transient vibration process under the impact load.The hydrodynamic calculation is an important part of equipment research.In this paper,firstly,combining the theory of the Euler-Bernoulli beam and the potential flow,the transfer equation of the Euler-Bernoulli beam considering the hydroelastic effect is derived,which expands the application scope of the transfer matrix.The correctness of the transfer matrix for the beam with hydroelastic behaviors is verified by comparison with the results of the finite element analysis.Then the dynamics model of the underwater launch system is established based on the multibody system transfer matrix method,and the beam with hydroelastic behaviors is employed as the external vehicle.Subsequently,the overall transfer and dynamic equation are derived,resulting in the solution of the wet natural frequency and the dynamic response under the impact load.The comparison with experimental data validates the dynamics model and simulation results and ensures its reliability in practical applications.The dynamic of the system demonstrates that the launching interval and adjacent tube effect will exert an influence on the subsequent emission.This research provides a fast and efficient method for the dynamic calculation of the underwater launch system.
