This paper addresses joint wind-wave induced dynamic responses of a semi-type offshore floating wind turbine（OFWT） under normal states and fault event conditions. The analysis in this paper is conducted in time doma...This paper addresses joint wind-wave induced dynamic responses of a semi-type offshore floating wind turbine（OFWT） under normal states and fault event conditions. The analysis in this paper is conducted in time domain, using an aero-hydro-servo-elastic simulation code-FAST. Owing to the unique viscous features of the reference system, the original viscous damping model implemented in FAST is replaced with a quadratic one to gain an accurate capture of viscous effects. Simulation cases involve free-decay motion in still water, steady motions in the presence of regular waves and wind as well as dynamic response in operational sea states with and without wind. Simulations also include the cases for transient responses induced by fast blade pitching after emergency shutdown. The features of platform motions, local structural loads and a typical mooring line tension force under a variety of excitations are obtained and investigated.展开更多
In this paper, adaptive genetic algorithm （AGA） is applied to topology optimization of truss structure with frequency domain excitations. The optimization constraints include fundamental frequency, displacement resp...In this paper, adaptive genetic algorithm （AGA） is applied to topology optimization of truss structure with frequency domain excitations. The optimization constraints include fundamental frequency, displacement responses under force excitations and acceleration responses under foundation acceleration excitations. The roulette wheel selection operator, adaptive crossover and mutation operators are used as genetic operators. Some heuristic strategies are put forward to direct the deletion of the extra bars and nodes on truss structures. Three examples demonstrate that the proposed method can yield the optimum structure form and the lightest weight of the given ground structure while satisfying dynamic response constraints.展开更多
It is essential to precisely predict the crack growth,especially the near-threshold regime crack growth under different stress ratios,for most engineering structures consume their fatigue lives in this regime under ra...It is essential to precisely predict the crack growth,especially the near-threshold regime crack growth under different stress ratios,for most engineering structures consume their fatigue lives in this regime under random loading.In this paper,an improved unique curve model is proposed based on the unique curve model,and the determination of the shape exponents of this model is provided.The crack growth rate curves of some materials taken from the literature are evaluated using the improved model,and the results indicate that the improved model can accurately predict the crack growth rate in the nearthreshold and Paris regimes.The improved unique curve model can solve the problems about the shape exponents determination and weak ability around the near-threshold regime meet in the unique curve model.In addition,the shape exponents in the improved model at negative stress ratios are discussed,which can directly adopt that in the unique curve model.展开更多
In previous studies, the nonlinear problem of electrohydrodynamic(EHD)ion drag flows in a circular cylindrical conduit has been studied by several authors. However, those studies seldom involve the computation for lar...In previous studies, the nonlinear problem of electrohydrodynamic(EHD)ion drag flows in a circular cylindrical conduit has been studied by several authors. However, those studies seldom involve the computation for large physical parameters such as the electrical Hartmann number and the magnitude parameter for the strength of the nonlinearity due to the existence of strong nonlinearity in these extreme cases. To overcome this faultiness, the newly-developed homotopy Coiflets wavelet method is extended to solve this EHD flow problem with strong nonlinearity. The validity and reliability of the proposed technique are verified. Particularly, the highly accurate homotopy-wavelet solution is obtained for extreme large parameters, which seems to be overlooked before.Discussion about the effects of related physical parameters on the axial velocity field is presented.展开更多
In this paper,we focus on the two-dimensional pulsating nanofluid flow through a parallel-plate channel in the presence of a magnetic field.The pulsating flow is produced by an applied pressure gradient that fluctuate...In this paper,we focus on the two-dimensional pulsating nanofluid flow through a parallel-plate channel in the presence of a magnetic field.The pulsating flow is produced by an applied pressure gradient that fluctuates with a small amplitude.A kind of proper transformation is used so that the governing equations describing the momentum and thermal energy are reduced to a set of non-dimensional equations.The analytical expressions of the pulsating velocity,temperature,and Nusselt number of nanofluids are obtained by the perturbation technique.In the present study,the effects of the Cu-H2O and Al_(2)O_(3)-H2O nanofluids on the flow and heat transfer in pulsating flow are compared and analyzed.The results show that the convective heat transfer effect of Cu-H2O nanofluids is better than that of Al_(2)O_(3)-H2O nanofluids.Also,the effects of the Hartmann number and pulsation amplitude on the velocity,temperature,and Nusselt number are examined and discussed in detail.The present work indicates that increasing the Hartmann number and pulsation amplitude can enhance the heat transfer of the pulsating flow.In addition,selecting an optimal pulsation frequency can maximize the convective heat transfer of the pulsating flow.Therefore,improved understanding of these fundamental mechanisms is conducive to the optimal design of thermal systems.展开更多
A fully developed steady immiscible flow of nanofluid in a two-layer microchannel is studied in the presence of electro-kinetic effects.Buongiorno’s model is employed for describing the behavior of nanofluids.Differe...A fully developed steady immiscible flow of nanofluid in a two-layer microchannel is studied in the presence of electro-kinetic effects.Buongiorno’s model is employed for describing the behavior of nanofluids.Different from the previous studies on two-layer channel flow of a nanofluid,the present paper introduces the flux conservation conditions for the nanoparticle volume fraction field,which makes this work new and unique,and it is in coincidence with practical observations.The governing equations are reduced into a group of ordinary differential equations via appropriate similarity transformations.The highly accurate analytical approximations are obtained.Important physical quantities and total entropy generation are analyzed and discussed.A comparison is made to determine the significance of electrical double layer(EDL)effects in the presence of an external electric field.It is found that the Brownian diffusion,the thermophoresis diffusion,and the viscosity have significant effects on altering the flow behaviors.展开更多
The Whitham-Broer-Kaup model is widely used to study the tsunami waves.The classical Whitham-Broer-Kaup equations are re-investigated in detail by the generalized projective Riccati-equation method.20 sets of solution...The Whitham-Broer-Kaup model is widely used to study the tsunami waves.The classical Whitham-Broer-Kaup equations are re-investigated in detail by the generalized projective Riccati-equation method.20 sets of solutions are obtained of which,to the best of the authors’knowledge,some have not been reported in literature.Bifurcation analysis of the planar dynamical systems is then used to show different phase portraits of the traveling wave solutions under various parametric conditions.展开更多
A new modification of false position method for solving nonlinear equations is presented by applying homotopy analysis method （HAM）. Some numerical illustrations are given to show the efficiency of algorithm.
We develop a mathematical model to describe the flow in a microchannel driven by the upper stretching wall of the channel in the presence of electrokinetic effects. In this model, we avoid imposing any unphysical boun...We develop a mathematical model to describe the flow in a microchannel driven by the upper stretching wall of the channel in the presence of electrokinetic effects. In this model, we avoid imposing any unphysical boundary condition, for instance, the zero electrostatic potential in the middle of the channel. Using the similarity transformation, we employ the homotopy analysis method （HAM） to get the analytical solution of the model. In our approach, the unknown pressure constant and the integral constant related to the electric potential are solved spontaneously by using the proper boundary conditions on the channel walls, which makes our model consistent with the commonly accepted models in the field of fluid mechanics. It is expected that our model can offer a general and proper way to study the flow phenomena in microchannels.展开更多
Two different methods to model a point absorber wave energy converter （WEC） with direct drive linear power take-off （PTO） are proposed in the present study： the frequency domain （FD） method and the time domain ...Two different methods to model a point absorber wave energy converter （WEC） with direct drive linear power take-off （PTO） are proposed in the present study： the frequency domain （FD） method and the time domain （TD） method. In the FD analysis, the frequency response function （FRF） of the WEC device is obtained via the equation of motion, and the expressions of power capture width in regular and random waves are derived as well. In the TD modeling, based on a state space approximation of the convolution term in the motion equation, both regular wave and random wave simulations are carded out. The regular wave simulation results indicate that the state space approximation is sufficiently accurate and the capture width reaches the maximum in the vicinity of the natural frequency. In the random wave simulations, the effects of buoy size, the PTO damping and wave climate on the power capture width are discussed in detail, which leads to the conclusion that the capture widths are influenced by the natural frequency of the WEC device, peak frequency of the wave spectrum, the amplitude of FRF and PTO damping. Furthermore, the increase of the capture width is at the cost of a relatively large buoy size and PTO damping when control is not included.展开更多
Numerous influence factors will lead to the inaccurate prediction of fatigue crack propagation(FCP)life of the metal structure based on the existing FCP model,while the prediction method based on machine learning(ML)a...Numerous influence factors will lead to the inaccurate prediction of fatigue crack propagation(FCP)life of the metal structure based on the existing FCP model,while the prediction method based on machine learning(ML)and data-driven approach can provide a new idea for accurately predicting the FCP life of the metal structure.In response to the inconvenience of the online prediction method and the inaccu-racy of the offline prediction method,an improved offline prediction method based on data feedback is presented in this paper.FCP tests of reduced scale models of balcony opening corners in a cruise ship are conducted to obtain experimental data with respect to the a-N curves.The crack length corresponding to the cycle is trained using a support vector regression(SVR)and back propagation neural network(BP NN)algorithms.FCP prediction lives of test specimens are performed according to the online,offline,and improved offline prediction methods.Effects of the number of feedback data,the sequence length(SL)in the input set,and the cycle interval on prediction accuracy are discussed.The generalization ability of the proposed method is validated by comparing the prediction results with the experimental data in the literature.The larger the number of feedback data,the higher the prediction accuracy.The results show that 1/5 and 1/2 feedback data are needed in the SVR and BP NN algorithm with SL is 5,respectively.Furthermore,the SVR algorithm and SL=5 are recommended for FCP life prediction using the improved offline prediction method.展开更多
Based on the homotopy analysis method, a general analytic technique for strongly nonlinear problems, a Maple package of automated derivation （ADHO） for periodic nonlinear oscillation systems is presented. This Maple...Based on the homotopy analysis method, a general analytic technique for strongly nonlinear problems, a Maple package of automated derivation （ADHO） for periodic nonlinear oscillation systems is presented. This Maple package is valid for periodic oscillation systems in rather general, and can automatically deliver the accurate approximations of the frequency co and the mean of motion δof a nonlinear periodic oscillator. Based on the homotopy analysis method which is valid even for highly nonlinear problems, this Maple package can give accurate approximate expressions even for nonlinear oscillation systems with strong nonlinearity. Besides, the package is user-friendly： One just needs to input a governing equation and initial conditions, and then gets satisfied analytic approximations in few seconds. Several different types of examples are given in this paper to illustrate the validity of this Maple package. Such kind of package provides us a helpful and easy-to-use tool in science and engineering to analyze periodic of this Maple package from the is published publicly. nonlinear oscillations. And it is free address http：//numericaltank.sjtu to download the electronic version edu.cn/sjliao.htm once the paper展开更多
In this paper,a simplified analytical method used to predict the residual ultimate strength of a ship hull after a shoal grounding accident is proposed.Shoal grounding accidents always lead to severe denting,though no...In this paper,a simplified analytical method used to predict the residual ultimate strength of a ship hull after a shoal grounding accident is proposed.Shoal grounding accidents always lead to severe denting,though not tearing,of the ship bottom structure,which may threaten the global hull girder resistance and result in even worse consequences,such as hull collapse.Here,the degree of damage of the bottom structure is predicted by a series of analytical methods based on the plastic-elastic deformation mechanism.The energy dissipation of a ship bottom structure is obtained from individual components to determine the sliding distance of the seabed obstruction.Then,a new approach to assess the residual strength of the damaged ship subjected to shoal grounding is proposed based on the improved Smith’s method.This analytical method is verified by comparing the results of the proposed method and those generated by numerical simulation using the software ABAQUS.The proposed analytical method can be used to assess the safety of a ship with a double bottom during its design phase and predict the residual ultimate strength of a ship after a shoal grounding accident occurs.展开更多
The non-similarity solution for natural convection from a permeable isothermal vertical wall is considered. The governing boundary-layer equations for non-similarity flow and temperature fields are solved using the ho...The non-similarity solution for natural convection from a permeable isothermal vertical wall is considered. The governing boundary-layer equations for non-similarity flow and temperature fields are solved using the homotopy analysis method. The homotopy-Pade’ technique is applied to accelerate the convergence of the homotopy-series solution. The influence of physical parameters on the non-similarity flows is investigated in detail. Different from the previous analytic results,the homotopy-series solutions are convergent and valid for all physical parameters in the whole domain 0 x 【 ∞ and 0 y 【 ∞.展开更多
This paper addresses the challenge of scarcity and discontinuity in spatio-temporal observation data within oceanographic research.The primary goal is to develop a robust model capable of generating missing wave heigh...This paper addresses the challenge of scarcity and discontinuity in spatio-temporal observation data within oceanographic research.The primary goal is to develop a robust model capable of generating missing wave height data and enhancing the understanding of ocean wave behavior.We propose an end-to-end spatio-temporal sequence generation network based on convolutional U-Net,utilizing reanalyzed atmospheric datasets from the European Centre for Medium-Range Weather Forecasts(ECMWF).The model incorporates input features such as wind wave height,wave direction,mean wave period,and wind speed to generate significant wind wave heights in the South China Sea at specified times.Data smoothing was applied at intervals of 12,24,and 36 h under both moderate and extreme wave conditions,resulting in wave height data at 6-hour intervals.The findings demonstrate that the model effectively captures areas with high wave heights,outperforming traditional interpolation-based methods,especially as input data time intervals increase and wave conditions intensify.This approach offers a novel solution for generating missing spatio-temporal data,providing valuable insights into ocean wave behavior and supporting applications in ocean engineering.展开更多
The Coiflet wavelet-homotopy Galerkin method is extended to solve unsteady nonlinear wave equations for the first time.The Korteweg-de Vries(KdV)equation,the Burgers equation and the Korteweg-de Vries-Burgers(KdVB)equ...The Coiflet wavelet-homotopy Galerkin method is extended to solve unsteady nonlinear wave equations for the first time.The Korteweg-de Vries(KdV)equation,the Burgers equation and the Korteweg-de Vries-Burgers(KdVB)equation are examined as illustrative examples.Validity and accuracy of the proposed method are assessed in terms of relative variance and the maximum error norm.Our results are found in good agreement with exact solutions and numerical solutions reported in previous studies.Furthermore,it is found that the solution accuracy is closely related to the resolution level and the convergence-control parameter.It is also found that our proposed method is superior to the traditional homotopy analysis method when dealing with unsteady nonlinear problems.It is expected that this approach can be further used to solve complicated unsteady problems in the fields of science and engineering.展开更多
In this paper,the natural convection of a complex fluid that contains both nanoparticles and gyrotactic microorganisms in a heated square cavity is considered.The Buongiorno model is applied to descirbe the nanofluid ...In this paper,the natural convection of a complex fluid that contains both nanoparticles and gyrotactic microorganisms in a heated square cavity is considered.The Buongiorno model is applied to descirbe the nanofluid behaviours.Both the top and bottom horizontal walls of the cavity are adiabatic,and there is a temperature difference between the left and right vertical walls.The non-dimensional governing equations are obtained when the stream-vorticity formulation of function is used,which are solved by the recently developed robust Coiflet wavelet homotopy analysis method.A rigid verification for the solver is given.Besides,the effects of various physics parameters including the Rayleigh number,the buoyancy ratio parameter,the bioconvection Rayleigh number,the Prandtl number,the Brownian motion parameter,the thermophoresis parameter,the heat generation parameter,the Lewis number,the bioconvection Peclet number and the Schmidt number on this complicated natural convection are examined.It is known that natural convection is closely related to our daily life owing to its wide existence in nature and engineering applications.We believe that our work will make a significant contribution to a better understanding of the natural convection of a complex fluid in a cavity with suspensions of both inorganic nanoparticles and organic microorganisms.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.51239007)
文摘This paper addresses joint wind-wave induced dynamic responses of a semi-type offshore floating wind turbine（OFWT） under normal states and fault event conditions. The analysis in this paper is conducted in time domain, using an aero-hydro-servo-elastic simulation code-FAST. Owing to the unique viscous features of the reference system, the original viscous damping model implemented in FAST is replaced with a quadratic one to gain an accurate capture of viscous effects. Simulation cases involve free-decay motion in still water, steady motions in the presence of regular waves and wind as well as dynamic response in operational sea states with and without wind. Simulations also include the cases for transient responses induced by fast blade pitching after emergency shutdown. The features of platform motions, local structural loads and a typical mooring line tension force under a variety of excitations are obtained and investigated.
基金Project supported by the Innovation Fund of Space Technology.
文摘In this paper, adaptive genetic algorithm （AGA） is applied to topology optimization of truss structure with frequency domain excitations. The optimization constraints include fundamental frequency, displacement responses under force excitations and acceleration responses under foundation acceleration excitations. The roulette wheel selection operator, adaptive crossover and mutation operators are used as genetic operators. Some heuristic strategies are put forward to direct the deletion of the extra bars and nodes on truss structures. Three examples demonstrate that the proposed method can yield the optimum structure form and the lightest weight of the given ground structure while satisfying dynamic response constraints.
文摘It is essential to precisely predict the crack growth,especially the near-threshold regime crack growth under different stress ratios,for most engineering structures consume their fatigue lives in this regime under random loading.In this paper,an improved unique curve model is proposed based on the unique curve model,and the determination of the shape exponents of this model is provided.The crack growth rate curves of some materials taken from the literature are evaluated using the improved model,and the results indicate that the improved model can accurately predict the crack growth rate in the nearthreshold and Paris regimes.The improved unique curve model can solve the problems about the shape exponents determination and weak ability around the near-threshold regime meet in the unique curve model.In addition,the shape exponents in the improved model at negative stress ratios are discussed,which can directly adopt that in the unique curve model.
基金the National Natural Science Foundation of China (No. 11872241)。
文摘In previous studies, the nonlinear problem of electrohydrodynamic(EHD)ion drag flows in a circular cylindrical conduit has been studied by several authors. However, those studies seldom involve the computation for large physical parameters such as the electrical Hartmann number and the magnitude parameter for the strength of the nonlinearity due to the existence of strong nonlinearity in these extreme cases. To overcome this faultiness, the newly-developed homotopy Coiflets wavelet method is extended to solve this EHD flow problem with strong nonlinearity. The validity and reliability of the proposed technique are verified. Particularly, the highly accurate homotopy-wavelet solution is obtained for extreme large parameters, which seems to be overlooked before.Discussion about the effects of related physical parameters on the axial velocity field is presented.
基金Project supported by the China Postdoctoral Science Foundation(No.2018M631909)the Doctor of Entrepreneurship and Innovation Project of Jiangsu Province(No.JSSCBS20221300)。
文摘In this paper,we focus on the two-dimensional pulsating nanofluid flow through a parallel-plate channel in the presence of a magnetic field.The pulsating flow is produced by an applied pressure gradient that fluctuates with a small amplitude.A kind of proper transformation is used so that the governing equations describing the momentum and thermal energy are reduced to a set of non-dimensional equations.The analytical expressions of the pulsating velocity,temperature,and Nusselt number of nanofluids are obtained by the perturbation technique.In the present study,the effects of the Cu-H2O and Al_(2)O_(3)-H2O nanofluids on the flow and heat transfer in pulsating flow are compared and analyzed.The results show that the convective heat transfer effect of Cu-H2O nanofluids is better than that of Al_(2)O_(3)-H2O nanofluids.Also,the effects of the Hartmann number and pulsation amplitude on the velocity,temperature,and Nusselt number are examined and discussed in detail.The present work indicates that increasing the Hartmann number and pulsation amplitude can enhance the heat transfer of the pulsating flow.In addition,selecting an optimal pulsation frequency can maximize the convective heat transfer of the pulsating flow.Therefore,improved understanding of these fundamental mechanisms is conducive to the optimal design of thermal systems.
基金Project supported by the National Natural Science Foundation of China(No.11872241)
文摘A fully developed steady immiscible flow of nanofluid in a two-layer microchannel is studied in the presence of electro-kinetic effects.Buongiorno’s model is employed for describing the behavior of nanofluids.Different from the previous studies on two-layer channel flow of a nanofluid,the present paper introduces the flux conservation conditions for the nanoparticle volume fraction field,which makes this work new and unique,and it is in coincidence with practical observations.The governing equations are reduced into a group of ordinary differential equations via appropriate similarity transformations.The highly accurate analytical approximations are obtained.Important physical quantities and total entropy generation are analyzed and discussed.A comparison is made to determine the significance of electrical double layer(EDL)effects in the presence of an external electric field.It is found that the Brownian diffusion,the thermophoresis diffusion,and the viscosity have significant effects on altering the flow behaviors.
基金Project supported by the National Natural Science Foundation of China(No.11872241)the Discovery Early Career Researcher Award(No.DE150100169)the Centre of Excellence Grant funded by the Australian Research Council(No.CE140100003)。
文摘The Whitham-Broer-Kaup model is widely used to study the tsunami waves.The classical Whitham-Broer-Kaup equations are re-investigated in detail by the generalized projective Riccati-equation method.20 sets of solutions are obtained of which,to the best of the authors’knowledge,some have not been reported in literature.Bifurcation analysis of the planar dynamical systems is then used to show different phase portraits of the traveling wave solutions under various parametric conditions.
文摘A new modification of false position method for solving nonlinear equations is presented by applying homotopy analysis method （HAM）. Some numerical illustrations are given to show the efficiency of algorithm.
基金supported in part by the Australian Research Council through a Discovery Early Career Researcher Award to Qiang SUN
文摘We develop a mathematical model to describe the flow in a microchannel driven by the upper stretching wall of the channel in the presence of electrokinetic effects. In this model, we avoid imposing any unphysical boundary condition, for instance, the zero electrostatic potential in the middle of the channel. Using the similarity transformation, we employ the homotopy analysis method （HAM） to get the analytical solution of the model. In our approach, the unknown pressure constant and the integral constant related to the electric potential are solved spontaneously by using the proper boundary conditions on the channel walls, which makes our model consistent with the commonly accepted models in the field of fluid mechanics. It is expected that our model can offer a general and proper way to study the flow phenomena in microchannels.
基金supported by the State Key Laboratory of Ocean Engineering,Shanghai Jiao Tong University(Grant No.GKZD010023)
文摘Two different methods to model a point absorber wave energy converter （WEC） with direct drive linear power take-off （PTO） are proposed in the present study： the frequency domain （FD） method and the time domain （TD） method. In the FD analysis, the frequency response function （FRF） of the WEC device is obtained via the equation of motion, and the expressions of power capture width in regular and random waves are derived as well. In the TD modeling, based on a state space approximation of the convolution term in the motion equation, both regular wave and random wave simulations are carded out. The regular wave simulation results indicate that the state space approximation is sufficiently accurate and the capture width reaches the maximum in the vicinity of the natural frequency. In the random wave simulations, the effects of buoy size, the PTO damping and wave climate on the power capture width are discussed in detail, which leads to the conclusion that the capture widths are influenced by the natural frequency of the WEC device, peak frequency of the wave spectrum, the amplitude of FRF and PTO damping. Furthermore, the increase of the capture width is at the cost of a relatively large buoy size and PTO damping when control is not included.
文摘Numerous influence factors will lead to the inaccurate prediction of fatigue crack propagation(FCP)life of the metal structure based on the existing FCP model,while the prediction method based on machine learning(ML)and data-driven approach can provide a new idea for accurately predicting the FCP life of the metal structure.In response to the inconvenience of the online prediction method and the inaccu-racy of the offline prediction method,an improved offline prediction method based on data feedback is presented in this paper.FCP tests of reduced scale models of balcony opening corners in a cruise ship are conducted to obtain experimental data with respect to the a-N curves.The crack length corresponding to the cycle is trained using a support vector regression(SVR)and back propagation neural network(BP NN)algorithms.FCP prediction lives of test specimens are performed according to the online,offline,and improved offline prediction methods.Effects of the number of feedback data,the sequence length(SL)in the input set,and the cycle interval on prediction accuracy are discussed.The generalization ability of the proposed method is validated by comparing the prediction results with the experimental data in the literature.The larger the number of feedback data,the higher the prediction accuracy.The results show that 1/5 and 1/2 feedback data are needed in the SVR and BP NN algorithm with SL is 5,respectively.Furthermore,the SVR algorithm and SL=5 are recommended for FCP life prediction using the improved offline prediction method.
基金supported by the National Science Foundation of China under Grant No.11071274
文摘Based on the homotopy analysis method, a general analytic technique for strongly nonlinear problems, a Maple package of automated derivation （ADHO） for periodic nonlinear oscillation systems is presented. This Maple package is valid for periodic oscillation systems in rather general, and can automatically deliver the accurate approximations of the frequency co and the mean of motion δof a nonlinear periodic oscillator. Based on the homotopy analysis method which is valid even for highly nonlinear problems, this Maple package can give accurate approximate expressions even for nonlinear oscillation systems with strong nonlinearity. Besides, the package is user-friendly： One just needs to input a governing equation and initial conditions, and then gets satisfied analytic approximations in few seconds. Several different types of examples are given in this paper to illustrate the validity of this Maple package. Such kind of package provides us a helpful and easy-to-use tool in science and engineering to analyze periodic of this Maple package from the is published publicly. nonlinear oscillations. And it is free address http：//numericaltank.sjtu to download the electronic version edu.cn/sjliao.htm once the paper
基金National Natural Science Foundation of China(Grant No.51239007)。
文摘In this paper,a simplified analytical method used to predict the residual ultimate strength of a ship hull after a shoal grounding accident is proposed.Shoal grounding accidents always lead to severe denting,though not tearing,of the ship bottom structure,which may threaten the global hull girder resistance and result in even worse consequences,such as hull collapse.Here,the degree of damage of the bottom structure is predicted by a series of analytical methods based on the plastic-elastic deformation mechanism.The energy dissipation of a ship bottom structure is obtained from individual components to determine the sliding distance of the seabed obstruction.Then,a new approach to assess the residual strength of the damaged ship subjected to shoal grounding is proposed based on the improved Smith’s method.This analytical method is verified by comparing the results of the proposed method and those generated by numerical simulation using the software ABAQUS.The proposed analytical method can be used to assess the safety of a ship with a double bottom during its design phase and predict the residual ultimate strength of a ship after a shoal grounding accident occurs.
基金partly supported by National Natural Science Foundation ofChina (Grant No. 10872129)State Key Lab of Ocean Engineering(Grant No. GKZD010002)
文摘The non-similarity solution for natural convection from a permeable isothermal vertical wall is considered. The governing boundary-layer equations for non-similarity flow and temperature fields are solved using the homotopy analysis method. The homotopy-Pade’ technique is applied to accelerate the convergence of the homotopy-series solution. The influence of physical parameters on the non-similarity flows is investigated in detail. Different from the previous analytic results,the homotopy-series solutions are convergent and valid for all physical parameters in the whole domain 0 x 【 ∞ and 0 y 【 ∞.
基金supported by the Fundamental Research Funds for the Central Universities.
文摘This paper addresses the challenge of scarcity and discontinuity in spatio-temporal observation data within oceanographic research.The primary goal is to develop a robust model capable of generating missing wave height data and enhancing the understanding of ocean wave behavior.We propose an end-to-end spatio-temporal sequence generation network based on convolutional U-Net,utilizing reanalyzed atmospheric datasets from the European Centre for Medium-Range Weather Forecasts(ECMWF).The model incorporates input features such as wind wave height,wave direction,mean wave period,and wind speed to generate significant wind wave heights in the South China Sea at specified times.Data smoothing was applied at intervals of 12,24,and 36 h under both moderate and extreme wave conditions,resulting in wave height data at 6-hour intervals.The findings demonstrate that the model effectively captures areas with high wave heights,outperforming traditional interpolation-based methods,especially as input data time intervals increase and wave conditions intensify.This approach offers a novel solution for generating missing spatio-temporal data,providing valuable insights into ocean wave behavior and supporting applications in ocean engineering.
文摘The Coiflet wavelet-homotopy Galerkin method is extended to solve unsteady nonlinear wave equations for the first time.The Korteweg-de Vries(KdV)equation,the Burgers equation and the Korteweg-de Vries-Burgers(KdVB)equation are examined as illustrative examples.Validity and accuracy of the proposed method are assessed in terms of relative variance and the maximum error norm.Our results are found in good agreement with exact solutions and numerical solutions reported in previous studies.Furthermore,it is found that the solution accuracy is closely related to the resolution level and the convergence-control parameter.It is also found that our proposed method is superior to the traditional homotopy analysis method when dealing with unsteady nonlinear problems.It is expected that this approach can be further used to solve complicated unsteady problems in the fields of science and engineering.
基金H.Xu is supported by the National Natural Science Foundation of China(Grant No.11872241)This work was partially supported by the Australian Research Council(ARC)through Grants DE150100169,FT160100357 and CE140100003。
文摘In this paper,the natural convection of a complex fluid that contains both nanoparticles and gyrotactic microorganisms in a heated square cavity is considered.The Buongiorno model is applied to descirbe the nanofluid behaviours.Both the top and bottom horizontal walls of the cavity are adiabatic,and there is a temperature difference between the left and right vertical walls.The non-dimensional governing equations are obtained when the stream-vorticity formulation of function is used,which are solved by the recently developed robust Coiflet wavelet homotopy analysis method.A rigid verification for the solver is given.Besides,the effects of various physics parameters including the Rayleigh number,the buoyancy ratio parameter,the bioconvection Rayleigh number,the Prandtl number,the Brownian motion parameter,the thermophoresis parameter,the heat generation parameter,the Lewis number,the bioconvection Peclet number and the Schmidt number on this complicated natural convection are examined.It is known that natural convection is closely related to our daily life owing to its wide existence in nature and engineering applications.We believe that our work will make a significant contribution to a better understanding of the natural convection of a complex fluid in a cavity with suspensions of both inorganic nanoparticles and organic microorganisms.
