The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering applications.The FIV suppression is of great importance for the security of ...The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering applications.The FIV suppression is of great importance for the security of many cylindrical structures.Many active and passive control methods have been employed for the vibration suppression of an isolated cylinder undergoing vortex-induced vibrations(VIV).The FIV suppression methods are mainly extended to the multiple cylinders from the vibration control of the isolated cylinder.Due to the mutual interference between the multiple cylinders,the FIV mechanism is more complex than the VIV mechanism,which makes a great challenge for the FIV suppression.Some efforts have been devoted to vibration suppression of multiple cylinder systems undergoing FIV over the past two decades.The control methods,such as helical strakes,splitter plates,control rods and flexible sheets,are not always effective,depending on many influence factors,such as the spacing ratio,the arrangement geometrical shape,the flow velocity and the parameters of the vibration control devices.The FIV response,hydrodynamic features and wake patterns of the multiple cylinders equipped with vibration control devices are reviewed and summarized.The FIV suppression efficiency of the vibration control methods are analyzed and compared considering different influence factors.Further research on the FIV suppression of multiple cylinders is suggested to provide insight for the development of FIV control methods and promote engineering applications of FIV control methods.展开更多
This paper investigates the hydrodynamic characteristics of floating truncated cylinders undergoing horizontal and vertical motions due to earthquake excitations in the finite water depth.The governing equation of the...This paper investigates the hydrodynamic characteristics of floating truncated cylinders undergoing horizontal and vertical motions due to earthquake excitations in the finite water depth.The governing equation of the hydrodynamic pressure acting on the cylinder is derived based on the radiation theory with the inviscid and incompressible assumptions.The governing equation is solved by using the method of separating variables and analytical solutions are obtained by assigning reasonable boundary conditions.The analytical result is validated by a numerical model using the exact artificial boundary simulation of the infinite water.The main variation and distribution characteristics of the hydrodynamic pressure acting on the side and bottom of the cylinder are analyzed for different combinations of wide-height and immersion ratios.The added mass coefficient of the cylinder is calculated by integrating the hydrodynamic pressure and simplified formulas are proposed for engineering applications.The calculation results show that the simplified formulas are in good agreement with the analytical solutions.展开更多
Within this work,we perform a sensitivity analysis to determine the influence of the material input parameters on the pressure in an isotropic porous solid cylinder.We provide a step-by-step guide to obtain the analyt...Within this work,we perform a sensitivity analysis to determine the influence of the material input parameters on the pressure in an isotropic porous solid cylinder.We provide a step-by-step guide to obtain the analytical solution for a porous isotropic elastic cylinder in terms of the pressure,stresses,and elastic displacement.We obtain the solution by performing a Laplace transform on the governing equations,which are those of Biot's poroelasticity in cylindrical polar coordinates.We enforce radial boundary conditions and obtain the solution in the Laplace transformed domain before reverting back to the time domain.The sensitivity analysis is then carried out,considering only the derived pressure solution.This analysis finds that the time t,Biot's modulus M,and Poisson's ratio ν have the highest influence on the pressure whereas the initial value of pressure P_(0) plays a very little role.展开更多
The accurate estimation of parameters is the premise for establishing a high-fidelity simulation model of a valve-controlled cylinder system.Bench test data are easily obtained,but it is challenging to emulate actual ...The accurate estimation of parameters is the premise for establishing a high-fidelity simulation model of a valve-controlled cylinder system.Bench test data are easily obtained,but it is challenging to emulate actual loads in the research on parameter estimation of valve-controlled cylinder system.Despite the actual load information contained in the operating data of the control valve,its acquisition remains challenging.This paper proposes a method that fuses bench test and operating data for parameter estimation to address the aforementioned problems.The proposed method is based on Bayesian theory,and its core is a pool fusion of prior information from bench test and operating data.Firstly,a system model is established,and the parameters in the model are analysed.Secondly,the bench and operating data of the system are collected.Then,the model parameters and weight coefficients are estimated using the data fusion method.Finally,the estimated effects of the data fusion method,Bayesian method,and particle swarm optimisation(PSO)algorithm on system model parameters are compared.The research shows that the weight coefficient represents the contribution of different prior information to the parameter estimation result.The effect of parameter estimation based on the data fusion method is better than that of the Bayesian method and the PSO algorithm.Increasing load complexity leads to a decrease in model accuracy,highlighting the crucial role of the data fusion method in parameter estimation studies.展开更多
The study of a droplet spreading on a circular cylinder under gravity was carried out using the pseudo-potential lattice Boltzmann high-density ratios multiphase model with a non-ideal Peng–Robinson equation of state...The study of a droplet spreading on a circular cylinder under gravity was carried out using the pseudo-potential lattice Boltzmann high-density ratios multiphase model with a non-ideal Peng–Robinson equation of state. The calculation results indicate that the motion of the droplet on the cylinder can be divided into three stages: spreading, sliding, and aggregating.The contact length and contact time of a droplet on a cylindrical surface can be affected by factors such as the wettability gradient of the cylindrical wall, the Bond number, and droplet size. Furthermore, phase diagrams showing the relationship between Bond number, cylinder wall wettability gradient, and contact time as well as maximum contact length for three different droplet sizes are given. A theoretical foundation for additional research into the heat and mass transfer process between the droplet and the cylinder can be established by comprehending the variable rules of maximum contact length and contact time.展开更多
The thermal behavior of an electrically non-conducting magnetic liquid flowing over a stretching cylinder under the influence of a magnetic dipole is considered.The governing nonlinear differential equations are solve...The thermal behavior of an electrically non-conducting magnetic liquid flowing over a stretching cylinder under the influence of a magnetic dipole is considered.The governing nonlinear differential equations are solved numerically using a finite element approach,which is properly validated through comparison with earlier results available in the literature.The results for the velocity and temperature fields are provided for different values of the Reynolds number,ferromagnetic response number,Prandtl number,and viscous dissipation parameter.The influence of some physical parameters on skin friction and heat transfer on the walls of the cylinder is also investigated.The applicability of this research to heat control in electronic devices is discussed to a certain extent.展开更多
A coupled Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)approach is used to calculate the interaction of a flexible rag transported by a fluid current with a fixed solid cylinder.More specifically a hyb...A coupled Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)approach is used to calculate the interaction of a flexible rag transported by a fluid current with a fixed solid cylinder.More specifically a hybrid Eulerian-Lagrangian approach is used with the rag being modeled as a set of interconnected particles.The influence of various parameters is considered,namely the inlet velocity(1.5,2.0,and 2.5 m/s,respectively),the angle formed by the initially straight rag with the flow direction(45°,60°and 90°,respectively),and the inlet position(90,100,and 110 mm,respectively).The results show that the flow rate has a significant impact on the permeability of the rag.The higher the flow rate,the higher the permeability and the rag speed difference.The angle has a minor effect on rag permeability,with 45°being the most favorable angle for permeability.The inlet position has a small impact on rag permeability,while reducing the initial distance between the rag an the cylinder makes it easier for rags to pass through.展开更多
This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional sh...This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional shear apparatus was utilized to conduct tests on remolded samples under both normal and frozen conditions to investigate the mechanical properties and deformation behavior of loess under complex stress conditions. The results indicate significant differences in the internal changes of soil particles, unfrozen water, and relative positions in soil samples under normal and frozen conditions, leading to noticeable variations in strength and strain development.In frozen state, loess experiences primarily compressive failure with a slow growth of cracks, while at normal temperature, it predominantly exhibits shear failure. With the increase in the principal stress angle, the deformation patterns of the soil samples under different conditions become essentially consistent, gradually transitioning from compression to extension, accompanied by a reduction in axial strength. The gradual increase in the principal stress axis angle(α) reduces the strength of the generalized shear stress and shear strain curves.Under an increasing α, frozen soil exhibits strain-hardening characteristics, with the maximum shear strength occurring at α = 45°. The intermediate principal stress coefficient(b) also significantly impacts the strength of frozen soil, with an increasing b resulting in a gradual decrease in generalized shear stress strength. This study provides a reference for comprehensively exploring the mechanical properties of soil under traffic load and a reliable theoretical basis for the design and maintenance of roadbeds.展开更多
This study investigates the flow and heat transfer of dusty Williamson (MHD) Nanofluid flow over a stretching permeable cylinder in a porous medium. Dusty Williamson Nanofluid was considered due to its thermal propert...This study investigates the flow and heat transfer of dusty Williamson (MHD) Nanofluid flow over a stretching permeable cylinder in a porous medium. Dusty Williamson Nanofluid was considered due to its thermal properties and potential benefits of increasing the heat transfer rate. Firstly, partial differential equations are transformed into coupled non-linear ordinary differential equations through a similarity variables transformation. The resulting set of dimensionless equations is solved analytically by using the Homogony Perturbation Method (HPM). The effects of the emerging parameters on the velocity and temperature profiles as well as skin-friction coefficient and Nusselt number are publicized through tables and graphs with appropriate discussions. The present result has been compared with published papers and found to be in agreement. To the best of author’s knowledge, there has been sparse research work in the literature that considers the effect of dust with Williamson Nanofluid and also solving the problem analytically. Therefore to the best of author’s knowledge, this is the first time analytical solution has been established for the problem. The results revealed that the fluid velocity of both the fluid and dust phases decreases as the Williamson parameter increases. Motivated by the above limitations and the gaps in past works, therefore, it is hoped that the present work will assist in providing accurate solutions to many practical problems in science, industry and engineering.展开更多
In engineering applications (Like an ocean riser), fluid flow around bluff bodies generates substantial resistance, which can jeopardize structural integrity, lifespan, and escalate resource consumption. Therefore, em...In engineering applications (Like an ocean riser), fluid flow around bluff bodies generates substantial resistance, which can jeopardize structural integrity, lifespan, and escalate resource consumption. Therefore, employing drag reduction measures becomes particularly crucial. This paper employs the immersed boundary method to investigate the impact of transversely oriented appendage plate flexibility on the drag of cylinders under different Reynolds numbers and distances. The results indicate that flexible appendage plate exerts drag reduction effects on the downstream cylinder, with this effect gradually diminishing as Reynolds numbers increase. At identical Reynolds numbers, the drag reduction effect initially increases and then decreases with distance, with the optimal drag reduction distance observed at D = 2.5. Compared to cylinders without appendage plate, the maximum drag reduction achieved is 30.551%. Addressing the drag reduction issue in cylinders holds significant importance for ensuring engineering structural integrity, enhancing engineering efficiency, and developing novel underwater towing systems.展开更多
Heat transfers due to MHD-conjugate free convection from the isothermal horizontal circular cylinder while viscosity is a function of temperature is investigated. The governing equations of the flow and connected boun...Heat transfers due to MHD-conjugate free convection from the isothermal horizontal circular cylinder while viscosity is a function of temperature is investigated. The governing equations of the flow and connected boundary conditions are made dimensionless using a set of non-dimensional parameters. The governing equations are solved numerically using the finite difference method. Numerical results are obtained for various values of viscosity variation parameter, Prandtl number, magnetic parameter, and conjugate conduction parameter for the velocity and the temperature within the boundary layer as well as the skin friction coefficients and heat transfer rate along the surface.展开更多
The Hong Kong–Zhuhai–Macao Bridge(HZMB)involved the installation of 120 mega-cylinders with a diameter of 22 m,weights up to 513 t,and penetration depths up to 33 m using an eight-vibratory hammer group.Due to the l...The Hong Kong–Zhuhai–Macao Bridge(HZMB)involved the installation of 120 mega-cylinders with a diameter of 22 m,weights up to 513 t,and penetration depths up to 33 m using an eight-vibratory hammer group.Due to the lack of engineering experience on the drivability of large-diameter cylinders under multiple vibratory hammers,predicting the penetration rate and time of steel cylinders is an open challenge that has a considerable impact on the construction control of the HZMB.In this study,the vibratory penetration of large-diameter steel cylinders in the HZMB is investigated based on geological surveys,field monitoring,and drivability analysis.The vibratory penetration rate,installation accuracy,and dynamic responses of the steel cylinders at both the eastern and western artificial islands are analyzed.The dynamic soil resistance has a great influence on the cylinder drivability.However,the current design methods for estimating the vibratory driving soil resistance are proven inaccurate without considering the scale effects.Therefore,a modified method with a normalized effective area ratio A_(r,eff)is proposed in this study to calculate the vibratory soil resistance for open-ended thin-wall cylinders under unplugged conditions.Considering the scale effects on the vibratory driving soil resistance,the proposed method leads to closer results to the measured data,providing a reference for future engineering practice.展开更多
Existing transversely isotropic poroelastodynamics solutions are limited to infinite domains and without experimental validation. Furthermore, there is a lack of analytical simulations for the elastic moduli dispersio...Existing transversely isotropic poroelastodynamics solutions are limited to infinite domains and without experimental validation. Furthermore, there is a lack of analytical simulations for the elastic moduli dispersion of fluid-saturated porous cylinders. To address these three limitations and investigate the mechanisms of moduli dispersion, we present the analytical solutions of the poromechanical responses and the elastic moduli dispersion of a transversely isotropic, fluid-saturated, finite porous cylinder subjected to a forced deformation test. Through an example, we demonstrate the effects of loading frequency, boundary conditions, and material's anisotropy, dimension, and permeability on the responses of pore pressure,force, displacement, and dynamic elastic moduli of the cylinder. The specimen's responses are significantly influenced by the frequency of the applied load, resulting in a drained state at low frequencies and an undrained state at high frequencies. At high frequencies, the sample behaves identically for an open or a closed lateral boundary, and permeability has insignificant effects. The dynamic elastic moduli are mainly controlled by the loading frequency and the ratio of the sample's radius to its height. Lastly,we show excellent matches between the newly derived analytical solution and laboratory measurements on one clay and two shale samples from Mont Terri.展开更多
The frequency-locked phenomenon commonly occurs in the vortex-induced vibration(VIV)of bluff bodies.Numerical simulation of this lock-in behavior is challenging,especially when the structure is positioned in close pro...The frequency-locked phenomenon commonly occurs in the vortex-induced vibration(VIV)of bluff bodies.Numerical simulation of this lock-in behavior is challenging,especially when the structure is positioned in close proximity to a solid boundary.To establish a robust simulator,an enhanced smoothed particle hydrodynamic(SPH)model is developed.The SPH model incorporates a particle shifting algorithm and a pressure correction algorithm to prevent cavity formation in the structure's wake area.A damping zone is also established near the outlet boundary to dissipate the vortices that shed from the structure.Additionally,GPU parallel technology is implemented to enhance the SPH model's computational efficiency.To validate the mo del,the predicted results are compared with the available refere nce data for flow past both stationary and oscillating cylinders.The verified SPH model is then employed to comparatively investigate the motion re sponse,lift characteristic,and vortex shedding mode of cylinders with and without accounting for the effect of boundary layers.Numerical analyses demonstrate that the developed SPH model is a proficient tool for efficiently simulating the vibration of near-wall bluff bodies at low Reynolds number.展开更多
Three-dimensional direct numerical simulations of the wake flow downstream of a near-wall circular cylinder at different gap ratios and boundary layer thicknesses are carried out by using the iterative immersed bounda...Three-dimensional direct numerical simulations of the wake flow downstream of a near-wall circular cylinder at different gap ratios and boundary layer thicknesses are carried out by using the iterative immersed boundary method.The non-dimensional gap between the cylinder and the wall,G/D=0.2,0.6 and 1.0,the non-dimensional boundary layer thickness,δ/D=0.0,0.7 and 1.6,the Reynolds number,Re=350,and the aspect ratio of the cylinder,L/D=25are adopted.High-resolution visualizations of the complex vortex structures at differentδ/D and G/D are presented.The transition of the streamwise vortex mode,the combined effects ofδ/D and G/D on the flow statistics,the pressure and shear stress distribution and the hydrodynamic forces are analyzed.Results show that with decreasing G/D and increasingδ/D,the gap flow and its vortex-shedding are significantly weakened,together with an elongated wake and an enlarged low-velocity area near the wall,leading to the wake mode transition from the two-sided to one-sided vortex-shedding.Different relative positions of the cylinder regarding the boundary layer alter the flow features of the shear layers.With an increase inδ/D,the front stagnation point shifts to the upper surface,and the distance between the flow divergence point and the maximum pressure position increases.The mean drag coefficient and r.m.s.values of drag and lift coefficients decrease with a decrease in G/D and an increase inδ/D,while the mean lift coefficient increases with decreasing G/D but decreases with increasingδ/D.展开更多
Vector accelerometer has attracted much attention for its great application potential in underground seismic signal measurement. We propose and demonstrate a novel vector accelerometer based on the three fiber Bragg g...Vector accelerometer has attracted much attention for its great application potential in underground seismic signal measurement. We propose and demonstrate a novel vector accelerometer based on the three fiber Bragg gratings(FBGs)embedded in a silicone rubber compliant cylinder at 120° distributed uniformly. The accelerometer is capable of detecting the orientation of vibration with a range of 0°–360° and the acceleration through monitoring the central wavelength shifts of three FBGs simultaneously. The experimental results show that the natural frequency of the accelerometer is about 85 Hz, and the sensitivity is 84.21 pm/g in the flat range of 20 Hz–60 Hz. Through experimental calibration, the designed accelerometer can accurately obtain vibration vector information, including vibration orientation and acceleration. In addition, the range of resonant frequency and sensitivity can be expanded by adjusting the hardness of the silicone rubber materials. Due to the characteristics of small size and orientation recognition, the accelerometer can be applied to low-frequency vibration acceleration vector measurement in narrow spaces.展开更多
Magnetically coupled rodless cylinders are widely used in the coordinate positioning of mechanical arms,electro-static paintings,and other industrial applications.However,they exhibit strong nonlinear characteristics,...Magnetically coupled rodless cylinders are widely used in the coordinate positioning of mechanical arms,electro-static paintings,and other industrial applications.However,they exhibit strong nonlinear characteristics,which lead to low servo control accuracy.In this study,a mass-flow equation through the valve port was derived to improve the control performance,considering the characteristics of the dynamics and throttle-hole flow.Subsequently,a fric-tion model combining static,viscous,and Coulomb friction with a zero-velocity interval was proposed.In addition,energy and dynamic models were set for the experimental investigation of the magnetically coupled rodless cylin-der.A nonlinear mathematical model for the position of the magnetically coupled rodless cylinder was proposed.An incremental PID controller was designed for the magnetically coupled rodless cylinder to control this system,and the PID parameters were adjusted online using RBF neural network.The response results of the PID parameters based on the RBF neural network were compared with those of the traditional incremental PID control,which proved the superiority of the optimization control algorithm of the incremental PID parameters based on the RBF neural network servo control system.The experimental results of this model were compared with the simulation results.The average error between the established model and the actual system was 0.005175054(m),which was approximately 2.588%of the total travel length,demonstrating the accuracy of the theoretical model.展开更多
A semi-analytical model is constructed to investigate two-dimensional radiation heat waves(Marshak waves)in a low-Z foam cylinder with a sleeve made of high-Z material.In this model,the energy loss to the high-Z wall ...A semi-analytical model is constructed to investigate two-dimensional radiation heat waves(Marshak waves)in a low-Z foam cylinder with a sleeve made of high-Z material.In this model,the energy loss to the high-Z wall is regarded as the primary two-dimensional effect and is taken into account via an indirect approach in which the energy loss is subtracted from the drive source and the wall loss is ignored.The interdependent Marshak waves in the low-Z foam and high-Z wall are used to estimate the energy loss.The energies and the heat front position calculated using the model under typical inertial confinement fusion conditions are verified by simulations.The validated model provides a theoretical tool for studying two-dimensional Marshak waves and should be helpful in providing further understanding of radiation transport.展开更多
In this paper, a free-surface synthetic schlieren(FS-SS) method was performed to detect the free surface disturbances. It is a purely optical method that uses refraction of light to reconstruct the height changes of w...In this paper, a free-surface synthetic schlieren(FS-SS) method was performed to detect the free surface disturbances. It is a purely optical method that uses refraction of light to reconstruct the height changes of water surface. The theory was developed based on Moisy's research, but has mainly been used in small-scale applications like painting and coating industry. Based on the methods and theories of the literature review, an in-depth investigation was conducted to optimize the FS-SS method and verify its feasibility on a relatively large-scale(e.g., wake region of shallow flow). The experimental setup was simplified which is approachable in most laboratories. Through proper experimental setting and an optimized post-processing routine, the quality of image was highly improved and ensured the accuracy of results. A drop test was performed proving the continuity of FS-SS method in the time domain. Also, a comparison test with flow around a cylinder at two speeds showed the ability of FS-SS method to reconstruct the irregular water surface in relative large-scale flow structures.展开更多
A higher order boundary element method(HOBEM)is presented for inviscid flow passing cylinders in bounded or unbounded domain.The traditional boundary integral equation is established with respect to the velocity poten...A higher order boundary element method(HOBEM)is presented for inviscid flow passing cylinders in bounded or unbounded domain.The traditional boundary integral equation is established with respect to the velocity potential and its normal derivative.In present work,a new integral equation is derived for the tangential velocity.The boundary is discretized into higher order elements to ensure the continuity of slope at the element nodes.The velocity potential is also expanded with higher order shape functions,in which the unknown coefficients involve the tangential velocity.The expansion then ensures the continuities of the velocity and the slope of the boundary at element nodes.Through extensive comparison of the results for the analytical solution of cylinders,it is shown that the present HOBEM is much more accurate than the conventional BEM.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U2106223,51979193,52301352)。
文摘The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering applications.The FIV suppression is of great importance for the security of many cylindrical structures.Many active and passive control methods have been employed for the vibration suppression of an isolated cylinder undergoing vortex-induced vibrations(VIV).The FIV suppression methods are mainly extended to the multiple cylinders from the vibration control of the isolated cylinder.Due to the mutual interference between the multiple cylinders,the FIV mechanism is more complex than the VIV mechanism,which makes a great challenge for the FIV suppression.Some efforts have been devoted to vibration suppression of multiple cylinder systems undergoing FIV over the past two decades.The control methods,such as helical strakes,splitter plates,control rods and flexible sheets,are not always effective,depending on many influence factors,such as the spacing ratio,the arrangement geometrical shape,the flow velocity and the parameters of the vibration control devices.The FIV response,hydrodynamic features and wake patterns of the multiple cylinders equipped with vibration control devices are reviewed and summarized.The FIV suppression efficiency of the vibration control methods are analyzed and compared considering different influence factors.Further research on the FIV suppression of multiple cylinders is suggested to provide insight for the development of FIV control methods and promote engineering applications of FIV control methods.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52078010 and 52101321)the National Key Research and Development Program of China(Grant No.2022YFC3004300).
文摘This paper investigates the hydrodynamic characteristics of floating truncated cylinders undergoing horizontal and vertical motions due to earthquake excitations in the finite water depth.The governing equation of the hydrodynamic pressure acting on the cylinder is derived based on the radiation theory with the inviscid and incompressible assumptions.The governing equation is solved by using the method of separating variables and analytical solutions are obtained by assigning reasonable boundary conditions.The analytical result is validated by a numerical model using the exact artificial boundary simulation of the infinite water.The main variation and distribution characteristics of the hydrodynamic pressure acting on the side and bottom of the cylinder are analyzed for different combinations of wide-height and immersion ratios.The added mass coefficient of the cylinder is calculated by integrating the hydrodynamic pressure and simplified formulas are proposed for engineering applications.The calculation results show that the simplified formulas are in good agreement with the analytical solutions.
基金Project supported by the Engineering and Physical Sciences Research Council of U. K.(Nos. EP/S030875/1, EP/T017899/1, and EP/T517896/1)。
文摘Within this work,we perform a sensitivity analysis to determine the influence of the material input parameters on the pressure in an isotropic porous solid cylinder.We provide a step-by-step guide to obtain the analytical solution for a porous isotropic elastic cylinder in terms of the pressure,stresses,and elastic displacement.We obtain the solution by performing a Laplace transform on the governing equations,which are those of Biot's poroelasticity in cylindrical polar coordinates.We enforce radial boundary conditions and obtain the solution in the Laplace transformed domain before reverting back to the time domain.The sensitivity analysis is then carried out,considering only the derived pressure solution.This analysis finds that the time t,Biot's modulus M,and Poisson's ratio ν have the highest influence on the pressure whereas the initial value of pressure P_(0) plays a very little role.
基金Supported by National Key R&D Program of China(Grant Nos.2020YFB1709901,2020YFB1709904)National Natural Science Foundation of China(Grant Nos.51975495,51905460)+1 种基金Guangdong Provincial Basic and Applied Basic Research Foundation of China(Grant No.2021-A1515012286)Science and Technology Plan Project of Fuzhou City of China(Grant No.2022-P-022).
文摘The accurate estimation of parameters is the premise for establishing a high-fidelity simulation model of a valve-controlled cylinder system.Bench test data are easily obtained,but it is challenging to emulate actual loads in the research on parameter estimation of valve-controlled cylinder system.Despite the actual load information contained in the operating data of the control valve,its acquisition remains challenging.This paper proposes a method that fuses bench test and operating data for parameter estimation to address the aforementioned problems.The proposed method is based on Bayesian theory,and its core is a pool fusion of prior information from bench test and operating data.Firstly,a system model is established,and the parameters in the model are analysed.Secondly,the bench and operating data of the system are collected.Then,the model parameters and weight coefficients are estimated using the data fusion method.Finally,the estimated effects of the data fusion method,Bayesian method,and particle swarm optimisation(PSO)algorithm on system model parameters are compared.The research shows that the weight coefficient represents the contribution of different prior information to the parameter estimation result.The effect of parameter estimation based on the data fusion method is better than that of the Bayesian method and the PSO algorithm.Increasing load complexity leads to a decrease in model accuracy,highlighting the crucial role of the data fusion method in parameter estimation studies.
文摘The study of a droplet spreading on a circular cylinder under gravity was carried out using the pseudo-potential lattice Boltzmann high-density ratios multiphase model with a non-ideal Peng–Robinson equation of state. The calculation results indicate that the motion of the droplet on the cylinder can be divided into three stages: spreading, sliding, and aggregating.The contact length and contact time of a droplet on a cylindrical surface can be affected by factors such as the wettability gradient of the cylindrical wall, the Bond number, and droplet size. Furthermore, phase diagrams showing the relationship between Bond number, cylinder wall wettability gradient, and contact time as well as maximum contact length for three different droplet sizes are given. A theoretical foundation for additional research into the heat and mass transfer process between the droplet and the cylinder can be established by comprehending the variable rules of maximum contact length and contact time.
文摘The thermal behavior of an electrically non-conducting magnetic liquid flowing over a stretching cylinder under the influence of a magnetic dipole is considered.The governing nonlinear differential equations are solved numerically using a finite element approach,which is properly validated through comparison with earlier results available in the literature.The results for the velocity and temperature fields are provided for different values of the Reynolds number,ferromagnetic response number,Prandtl number,and viscous dissipation parameter.The influence of some physical parameters on skin friction and heat transfer on the walls of the cylinder is also investigated.The applicability of this research to heat control in electronic devices is discussed to a certain extent.
基金funded by the Zhejiang Provincial Natural Science Foundation of China(Grant Nos.LY21E060004,LGG22E060011)National Natural Science Foundation of China(Grant No.51976193).
文摘A coupled Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)approach is used to calculate the interaction of a flexible rag transported by a fluid current with a fixed solid cylinder.More specifically a hybrid Eulerian-Lagrangian approach is used with the rag being modeled as a set of interconnected particles.The influence of various parameters is considered,namely the inlet velocity(1.5,2.0,and 2.5 m/s,respectively),the angle formed by the initially straight rag with the flow direction(45°,60°and 90°,respectively),and the inlet position(90,100,and 110 mm,respectively).The results show that the flow rate has a significant impact on the permeability of the rag.The higher the flow rate,the higher the permeability and the rag speed difference.The angle has a minor effect on rag permeability,with 45°being the most favorable angle for permeability.The inlet position has a small impact on rag permeability,while reducing the initial distance between the rag an the cylinder makes it easier for rags to pass through.
基金This work was supported by the National Natural Science Foundation of China(Nos.42161026&41801046)the Natural Science Foundation of Qinghai Province(No.2023-ZJ-934M)the Youth Research Foundation of Qinghai University(No.2022-QGY-5).
文摘This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional shear apparatus was utilized to conduct tests on remolded samples under both normal and frozen conditions to investigate the mechanical properties and deformation behavior of loess under complex stress conditions. The results indicate significant differences in the internal changes of soil particles, unfrozen water, and relative positions in soil samples under normal and frozen conditions, leading to noticeable variations in strength and strain development.In frozen state, loess experiences primarily compressive failure with a slow growth of cracks, while at normal temperature, it predominantly exhibits shear failure. With the increase in the principal stress angle, the deformation patterns of the soil samples under different conditions become essentially consistent, gradually transitioning from compression to extension, accompanied by a reduction in axial strength. The gradual increase in the principal stress axis angle(α) reduces the strength of the generalized shear stress and shear strain curves.Under an increasing α, frozen soil exhibits strain-hardening characteristics, with the maximum shear strength occurring at α = 45°. The intermediate principal stress coefficient(b) also significantly impacts the strength of frozen soil, with an increasing b resulting in a gradual decrease in generalized shear stress strength. This study provides a reference for comprehensively exploring the mechanical properties of soil under traffic load and a reliable theoretical basis for the design and maintenance of roadbeds.
文摘This study investigates the flow and heat transfer of dusty Williamson (MHD) Nanofluid flow over a stretching permeable cylinder in a porous medium. Dusty Williamson Nanofluid was considered due to its thermal properties and potential benefits of increasing the heat transfer rate. Firstly, partial differential equations are transformed into coupled non-linear ordinary differential equations through a similarity variables transformation. The resulting set of dimensionless equations is solved analytically by using the Homogony Perturbation Method (HPM). The effects of the emerging parameters on the velocity and temperature profiles as well as skin-friction coefficient and Nusselt number are publicized through tables and graphs with appropriate discussions. The present result has been compared with published papers and found to be in agreement. To the best of author’s knowledge, there has been sparse research work in the literature that considers the effect of dust with Williamson Nanofluid and also solving the problem analytically. Therefore to the best of author’s knowledge, this is the first time analytical solution has been established for the problem. The results revealed that the fluid velocity of both the fluid and dust phases decreases as the Williamson parameter increases. Motivated by the above limitations and the gaps in past works, therefore, it is hoped that the present work will assist in providing accurate solutions to many practical problems in science, industry and engineering.
文摘In engineering applications (Like an ocean riser), fluid flow around bluff bodies generates substantial resistance, which can jeopardize structural integrity, lifespan, and escalate resource consumption. Therefore, employing drag reduction measures becomes particularly crucial. This paper employs the immersed boundary method to investigate the impact of transversely oriented appendage plate flexibility on the drag of cylinders under different Reynolds numbers and distances. The results indicate that flexible appendage plate exerts drag reduction effects on the downstream cylinder, with this effect gradually diminishing as Reynolds numbers increase. At identical Reynolds numbers, the drag reduction effect initially increases and then decreases with distance, with the optimal drag reduction distance observed at D = 2.5. Compared to cylinders without appendage plate, the maximum drag reduction achieved is 30.551%. Addressing the drag reduction issue in cylinders holds significant importance for ensuring engineering structural integrity, enhancing engineering efficiency, and developing novel underwater towing systems.
文摘Heat transfers due to MHD-conjugate free convection from the isothermal horizontal circular cylinder while viscosity is a function of temperature is investigated. The governing equations of the flow and connected boundary conditions are made dimensionless using a set of non-dimensional parameters. The governing equations are solved numerically using the finite difference method. Numerical results are obtained for various values of viscosity variation parameter, Prandtl number, magnetic parameter, and conjugate conduction parameter for the velocity and the temperature within the boundary layer as well as the skin friction coefficients and heat transfer rate along the surface.
基金supported by the National Natural Science Foundation of China(52001267)Tianjin Port Engineering Institute Co.,Ltd.,and Eunsung O&C Offshore Marine and Construction(EUNSUNG19EG01).
文摘The Hong Kong–Zhuhai–Macao Bridge(HZMB)involved the installation of 120 mega-cylinders with a diameter of 22 m,weights up to 513 t,and penetration depths up to 33 m using an eight-vibratory hammer group.Due to the lack of engineering experience on the drivability of large-diameter cylinders under multiple vibratory hammers,predicting the penetration rate and time of steel cylinders is an open challenge that has a considerable impact on the construction control of the HZMB.In this study,the vibratory penetration of large-diameter steel cylinders in the HZMB is investigated based on geological surveys,field monitoring,and drivability analysis.The vibratory penetration rate,installation accuracy,and dynamic responses of the steel cylinders at both the eastern and western artificial islands are analyzed.The dynamic soil resistance has a great influence on the cylinder drivability.However,the current design methods for estimating the vibratory driving soil resistance are proven inaccurate without considering the scale effects.Therefore,a modified method with a normalized effective area ratio A_(r,eff)is proposed in this study to calculate the vibratory soil resistance for open-ended thin-wall cylinders under unplugged conditions.Considering the scale effects on the vibratory driving soil resistance,the proposed method leads to closer results to the measured data,providing a reference for future engineering practice.
文摘Existing transversely isotropic poroelastodynamics solutions are limited to infinite domains and without experimental validation. Furthermore, there is a lack of analytical simulations for the elastic moduli dispersion of fluid-saturated porous cylinders. To address these three limitations and investigate the mechanisms of moduli dispersion, we present the analytical solutions of the poromechanical responses and the elastic moduli dispersion of a transversely isotropic, fluid-saturated, finite porous cylinder subjected to a forced deformation test. Through an example, we demonstrate the effects of loading frequency, boundary conditions, and material's anisotropy, dimension, and permeability on the responses of pore pressure,force, displacement, and dynamic elastic moduli of the cylinder. The specimen's responses are significantly influenced by the frequency of the applied load, resulting in a drained state at low frequencies and an undrained state at high frequencies. At high frequencies, the sample behaves identically for an open or a closed lateral boundary, and permeability has insignificant effects. The dynamic elastic moduli are mainly controlled by the loading frequency and the ratio of the sample's radius to its height. Lastly,we show excellent matches between the newly derived analytical solution and laboratory measurements on one clay and two shale samples from Mont Terri.
基金financially supported by the National Natural Science Foundation of China (Grant Nos.52101312 and 51979028)the Basic and Applied Basic Research Foundation of Guangdong Province (Grant Nos.2022A1515240014 and 2023A1515011000)+1 种基金the Basic and Applied Basic Research Project of Guangzhou (Grant No.202201010240)the Project supported by SKL of HESS (Grant No.HESS-2012)。
文摘The frequency-locked phenomenon commonly occurs in the vortex-induced vibration(VIV)of bluff bodies.Numerical simulation of this lock-in behavior is challenging,especially when the structure is positioned in close proximity to a solid boundary.To establish a robust simulator,an enhanced smoothed particle hydrodynamic(SPH)model is developed.The SPH model incorporates a particle shifting algorithm and a pressure correction algorithm to prevent cavity formation in the structure's wake area.A damping zone is also established near the outlet boundary to dissipate the vortices that shed from the structure.Additionally,GPU parallel technology is implemented to enhance the SPH model's computational efficiency.To validate the mo del,the predicted results are compared with the available refere nce data for flow past both stationary and oscillating cylinders.The verified SPH model is then employed to comparatively investigate the motion re sponse,lift characteristic,and vortex shedding mode of cylinders with and without accounting for the effect of boundary layers.Numerical analyses demonstrate that the developed SPH model is a proficient tool for efficiently simulating the vibration of near-wall bluff bodies at low Reynolds number.
基金financially supported by the National Key R&D Program of China (Grant No.2022YFB2603000)the National Natural Science Foundation of China (Grant Nos.51779172 and 52179076)。
文摘Three-dimensional direct numerical simulations of the wake flow downstream of a near-wall circular cylinder at different gap ratios and boundary layer thicknesses are carried out by using the iterative immersed boundary method.The non-dimensional gap between the cylinder and the wall,G/D=0.2,0.6 and 1.0,the non-dimensional boundary layer thickness,δ/D=0.0,0.7 and 1.6,the Reynolds number,Re=350,and the aspect ratio of the cylinder,L/D=25are adopted.High-resolution visualizations of the complex vortex structures at differentδ/D and G/D are presented.The transition of the streamwise vortex mode,the combined effects ofδ/D and G/D on the flow statistics,the pressure and shear stress distribution and the hydrodynamic forces are analyzed.Results show that with decreasing G/D and increasingδ/D,the gap flow and its vortex-shedding are significantly weakened,together with an elongated wake and an enlarged low-velocity area near the wall,leading to the wake mode transition from the two-sided to one-sided vortex-shedding.Different relative positions of the cylinder regarding the boundary layer alter the flow features of the shear layers.With an increase inδ/D,the front stagnation point shifts to the upper surface,and the distance between the flow divergence point and the maximum pressure position increases.The mean drag coefficient and r.m.s.values of drag and lift coefficients decrease with a decrease in G/D and an increase inδ/D,while the mean lift coefficient increases with decreasing G/D but decreases with increasingδ/D.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61927812, 61735014, and 62105261)。
文摘Vector accelerometer has attracted much attention for its great application potential in underground seismic signal measurement. We propose and demonstrate a novel vector accelerometer based on the three fiber Bragg gratings(FBGs)embedded in a silicone rubber compliant cylinder at 120° distributed uniformly. The accelerometer is capable of detecting the orientation of vibration with a range of 0°–360° and the acceleration through monitoring the central wavelength shifts of three FBGs simultaneously. The experimental results show that the natural frequency of the accelerometer is about 85 Hz, and the sensitivity is 84.21 pm/g in the flat range of 20 Hz–60 Hz. Through experimental calibration, the designed accelerometer can accurately obtain vibration vector information, including vibration orientation and acceleration. In addition, the range of resonant frequency and sensitivity can be expanded by adjusting the hardness of the silicone rubber materials. Due to the characteristics of small size and orientation recognition, the accelerometer can be applied to low-frequency vibration acceleration vector measurement in narrow spaces.
基金Supported by Outstanding Young Scientists in Beijing of China(Grant No.BJJWZYJH01201910006021)Open Foundation of the State Key Laboratory of Fluid Power and Mechatronic Systems of China(Grant No.GZKF-202016)+2 种基金Henan Provincial Science and Technology Key Project of China(Grant Nos.202102210081,212102210050)Sub Project of Strengthening Key Basic Research Projects in the Basic Plan of the Science and Technology Commission of the Central Military Commission of China(Grant No.2019-JCJQ-ZD-120-13)Henan Provincial Fundamental Research Funds for the Universities of China(Grant No.NSFRF200403).
文摘Magnetically coupled rodless cylinders are widely used in the coordinate positioning of mechanical arms,electro-static paintings,and other industrial applications.However,they exhibit strong nonlinear characteristics,which lead to low servo control accuracy.In this study,a mass-flow equation through the valve port was derived to improve the control performance,considering the characteristics of the dynamics and throttle-hole flow.Subsequently,a fric-tion model combining static,viscous,and Coulomb friction with a zero-velocity interval was proposed.In addition,energy and dynamic models were set for the experimental investigation of the magnetically coupled rodless cylin-der.A nonlinear mathematical model for the position of the magnetically coupled rodless cylinder was proposed.An incremental PID controller was designed for the magnetically coupled rodless cylinder to control this system,and the PID parameters were adjusted online using RBF neural network.The response results of the PID parameters based on the RBF neural network were compared with those of the traditional incremental PID control,which proved the superiority of the optimization control algorithm of the incremental PID parameters based on the RBF neural network servo control system.The experimental results of this model were compared with the simulation results.The average error between the established model and the actual system was 0.005175054(m),which was approximately 2.588%of the total travel length,demonstrating the accuracy of the theoretical model.
基金supported by the State Key Laboratory of Laser Interaction with Mat-ter under Grant No.SKLLIM2108the China Postdoctoral Science Foundation under Grant No.2021M690468.
文摘A semi-analytical model is constructed to investigate two-dimensional radiation heat waves(Marshak waves)in a low-Z foam cylinder with a sleeve made of high-Z material.In this model,the energy loss to the high-Z wall is regarded as the primary two-dimensional effect and is taken into account via an indirect approach in which the energy loss is subtracted from the drive source and the wall loss is ignored.The interdependent Marshak waves in the low-Z foam and high-Z wall are used to estimate the energy loss.The energies and the heat front position calculated using the model under typical inertial confinement fusion conditions are verified by simulations.The validated model provides a theoretical tool for studying two-dimensional Marshak waves and should be helpful in providing further understanding of radiation transport.
基金Sponsored by the Key-Area Research and Development Program of Guangdong Province (Grant No.2020B1111010001)。
文摘In this paper, a free-surface synthetic schlieren(FS-SS) method was performed to detect the free surface disturbances. It is a purely optical method that uses refraction of light to reconstruct the height changes of water surface. The theory was developed based on Moisy's research, but has mainly been used in small-scale applications like painting and coating industry. Based on the methods and theories of the literature review, an in-depth investigation was conducted to optimize the FS-SS method and verify its feasibility on a relatively large-scale(e.g., wake region of shallow flow). The experimental setup was simplified which is approachable in most laboratories. Through proper experimental setting and an optimized post-processing routine, the quality of image was highly improved and ensured the accuracy of results. A drop test was performed proving the continuity of FS-SS method in the time domain. Also, a comparison test with flow around a cylinder at two speeds showed the ability of FS-SS method to reconstruct the irregular water surface in relative large-scale flow structures.
基金financially supported by the National Natural Science Foundation of China (Grant Nos.52271276,52271319,and 52201364)the Natural Science Foundation of Jiangsu Province (Grant No.BK20201006)。
文摘A higher order boundary element method(HOBEM)is presented for inviscid flow passing cylinders in bounded or unbounded domain.The traditional boundary integral equation is established with respect to the velocity potential and its normal derivative.In present work,a new integral equation is derived for the tangential velocity.The boundary is discretized into higher order elements to ensure the continuity of slope at the element nodes.The velocity potential is also expanded with higher order shape functions,in which the unknown coefficients involve the tangential velocity.The expansion then ensures the continuities of the velocity and the slope of the boundary at element nodes.Through extensive comparison of the results for the analytical solution of cylinders,it is shown that the present HOBEM is much more accurate than the conventional BEM.