Shot peening is a widely used surface treatment method by generating compressive residual stress near the surface of metallic materials to increase fatigue life and re- sistance to corrosion fatigue, cracking, etc. Co...Shot peening is a widely used surface treatment method by generating compressive residual stress near the surface of metallic materials to increase fatigue life and re- sistance to corrosion fatigue, cracking, etc. Compressive re- sidual stress and dent profile are important factors to eval- uate the effectiveness of shot peening process. In this pa- per, the influence of dimensionless parameters on maximum compressive residual stress and maximum depth of the dent were investigated. Firstly, dimensionless relations of pro- cessing parameters that affect the maximum compressive residual stress and the maximum depth of the dent were de- duced by dimensional analysis method. Secondly, the in- fluence of each dimensionless parameter on dimensionless variables was investigated by the finite element method. Fur- thermore, related empirical formulas were given for each di- mensionless parameter based on the simulation results. Fi- nally, comparison was made and good agreement was found between the simulation results and the empirical formula, which shows that a useful approach is provided in this pa- per for analyzing the influence of each individual parameter.展开更多
As a popular meshfree particle method,the smoothed particle hydrodynamics(SPH) has suffered from not being able to di-rectly implement the solid boundary conditions.This influences the SPH approximation accuracy and h...As a popular meshfree particle method,the smoothed particle hydrodynamics(SPH) has suffered from not being able to di-rectly implement the solid boundary conditions.This influences the SPH approximation accuracy and hinders its further de-velopment and application to engineering and scientific problems.In this paper,a coupled dynamic solid boundary treatment(SBT) algorithm has been proposed,after investigating the features of existing SPH SBT algorithms.The novelty of the cou-pled dynamic SBT algorithm includes a new repulsive force between approaching fluid and solid particles,and a new numeri-cal approximation scheme for estimating field functions of virtual solid particles.The new SBT algorithm has been examined with three numerical examples including a typical dam-break flow,a dam-break flow with a sharp-edged obstacle,and a water entry problem.It is demonstrated that SPH with this coupled dynamic boundary algorithm can lead to accurate results with smooth pressure field,and that the new SBT algorithm is also suitable for complex and even moving solid boundaries.展开更多
This article proposes a new wake oscillator model for vortex induced vibrations of an elastically supported rigid circular cylinder in a uniform current. The near wake dynamics related with the fluctuating nature of v...This article proposes a new wake oscillator model for vortex induced vibrations of an elastically supported rigid circular cylinder in a uniform current. The near wake dynamics related with the fluctuating nature of vortex shedding is modeled based on the classical van der Pol equation, combined with the equation for the oscillatory motion of the body. An appropriate approach is developed to estimate the empirical parameters in the wake oscillator model. The present predicted results are compared to the experimental data and previous wake oscillator model results. Good agreement with experimental results is found.展开更多
Thermally induced evolution of phase transformations is a basic physical-chemical process in the dissociation of gas hydrate in sediment (GHS). Heat transfer leads to the weakening of the bed soil and the simultaneous...Thermally induced evolution of phase transformations is a basic physical-chemical process in the dissociation of gas hydrate in sediment (GHS). Heat transfer leads to the weakening of the bed soil and the simultaneous establishment of a time varying stress field accompanied by seepage of fluids and deformation of the soil. As a consequence, ground failure could occur causing engineering damage or/and environmental disaster. This paper presents a simplified analysis of the thermal process by assuming that thermal conduction can be decoupled from the flow and deformation process. It is further assumed that phase transformations take place instantaneously. Analytical and numerical results are given for several examples of simplified geometry. Experiments using Tetra-hydro-furan hydrate sediments were carried out in our laboratory to check the theory. By comparison, the theoretical, numerical and experimental results on the evolution of dissociation fronts and temperature in the sediment are found to be in good agreement.展开更多
With the speed upgrade of the high-speed train,the aerodynamic drag becomes one of the key factors to restrain the train speed and energy saving.In order to reduce the aerodynamic drag of train head,a new parametric a...With the speed upgrade of the high-speed train,the aerodynamic drag becomes one of the key factors to restrain the train speed and energy saving.In order to reduce the aerodynamic drag of train head,a new parametric approach called local shape function(LSF) was adopted based on the free form surface deformation(FFD) method and a new efficient optimization method based on the response surface method(RSM) of GA-GRNN.The optimization results show that the parametric method can control the large deformation with a few design parameters,and can ensure the deformation zones smoothness and smooth transition of different deformation regions.With the same sample points for training,GA-GRNN performs better than GRNN to get the global optimal solution.As an example,the aerodynamic drag for a simplified shape with head + one carriage + tail train is reduced by 8.7%.The proposed optimization method is efficient for the engineering design of high-speed train.展开更多
The oil/water separation in a liquid-liquid cylindrical cyclone is experimentally studied in this article.The effects of the flow split-ratio and the flow rate on the oil/water separation performance are determined.Fr...The oil/water separation in a liquid-liquid cylindrical cyclone is experimentally studied in this article.The effects of the flow split-ratio and the flow rate on the oil/water separation performance are determined.From the experimental results,it is shown that with the increase of the flow split-ratio,the oil/water separation efficiency is enhanced at first,and an optimal flow split-ratio exists,beyond that optimal split-ratio,the watercut in the underflow keeps constant,while the oil content in the overflow begins to decrease.The process of the oil core structure formation and the phase distribution in the cyclone are determined by numerical simulations.Furthermore,the dependence of the separation efficiency on the Reynolds number and the flow split-ratio is investigated based on a dimensional analysis.A comparison between the predicted values and the experimental data shows a good agreement.展开更多
The initiation of pipeline spanning involves the coupling between the flow over the pipeline and the seepage-flow in the soil underneath the pipeline.The pipeline spanning initiation is experimentally observed and dis...The initiation of pipeline spanning involves the coupling between the flow over the pipeline and the seepage-flow in the soil underneath the pipeline.The pipeline spanning initiation is experimentally observed and discussed in this article.It is qualitatively indicated that the pressure-drop induced soil seepage failure is the predominant cause for pipeline spanning initiation.A flow-pipe-seepage sequential coupling Finite Element Method（FEM） model is proposed to simulate the coupling between the water flow-field and the soil seepage-field.A critical hydraulic gradient is obtained for oblique seepage failure of the sand in the direction tangent to the pipe.Parametric study is performed to investigate the effects of inflow velocity,pipe embedment on the pressure-drop,and the effects of soil internal friction angle and pipe embedment-to-diameter ratio on the critical flow velocity for pipeline spanning initiation.It is indicated that the dimensionless critical flow velocity changes approximately linearly with the soil internal friction angle for the submarine pipeline partially-embedded in a sandy seabed.展开更多
The prediction of the pressure wave amplitude produced when two trains pass each other in the tunnel is important to the train design for airtightness and tunnel conditions in China.In this paper,the key factors of th...The prediction of the pressure wave amplitude produced when two trains pass each other in the tunnel is important to the train design for airtightness and tunnel conditions in China.In this paper,the key factors of this problem were firstly stud-ied based on theoretical analysis.The equation of the worst tunnel length for the global maximum and minimum pressure values was derived.Then,the influence of tunnel length on global minimum pressure and the critical region in which the global minimum pressure varies rapidly were investigated.Finally,a numerical method based on two-dimensional Na-vier-Stokes equations was established.Typical conditions of two trains passing-by in tunnels of different lengths were simulated.The theoretical and computational results agree with each other closely.展开更多
基金supported by the National Natural Science Foun-dation of China (10972228,11002150,and 91016025)the Basic Research Equipment Project of Chinese Academy of Sciences(YZ200930)
文摘Shot peening is a widely used surface treatment method by generating compressive residual stress near the surface of metallic materials to increase fatigue life and re- sistance to corrosion fatigue, cracking, etc. Compressive re- sidual stress and dent profile are important factors to eval- uate the effectiveness of shot peening process. In this pa- per, the influence of dimensionless parameters on maximum compressive residual stress and maximum depth of the dent were investigated. Firstly, dimensionless relations of pro- cessing parameters that affect the maximum compressive residual stress and the maximum depth of the dent were de- duced by dimensional analysis method. Secondly, the in- fluence of each dimensionless parameter on dimensionless variables was investigated by the finite element method. Fur- thermore, related empirical formulas were given for each di- mensionless parameter based on the simulation results. Fi- nally, comparison was made and good agreement was found between the simulation results and the empirical formula, which shows that a useful approach is provided in this pa- per for analyzing the influence of each individual parameter.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10942004, 11172306)the National Defense Innovation Funds of the Chinese Academy of Sciences (Grant No. Y175031XML)
文摘As a popular meshfree particle method,the smoothed particle hydrodynamics(SPH) has suffered from not being able to di-rectly implement the solid boundary conditions.This influences the SPH approximation accuracy and hinders its further de-velopment and application to engineering and scientific problems.In this paper,a coupled dynamic solid boundary treatment(SBT) algorithm has been proposed,after investigating the features of existing SPH SBT algorithms.The novelty of the cou-pled dynamic SBT algorithm includes a new repulsive force between approaching fluid and solid particles,and a new numeri-cal approximation scheme for estimating field functions of virtual solid particles.The new SBT algorithm has been examined with three numerical examples including a typical dam-break flow,a dam-break flow with a sharp-edged obstacle,and a water entry problem.It is demonstrated that SPH with this coupled dynamic boundary algorithm can lead to accurate results with smooth pressure field,and that the new SBT algorithm is also suitable for complex and even moving solid boundaries.
基金supported by the National High Technology Research and Development Program of China(863 Program,Grant No.2006AA09Z350)the National Natural Science Foundation of China(Grant No.10702073)the Knowledge Innovation Program of Chinese Academy of Sciences(Grant No.KJCX2-YW-L02)
文摘This article proposes a new wake oscillator model for vortex induced vibrations of an elastically supported rigid circular cylinder in a uniform current. The near wake dynamics related with the fluctuating nature of vortex shedding is modeled based on the classical van der Pol equation, combined with the equation for the oscillatory motion of the body. An appropriate approach is developed to estimate the empirical parameters in the wake oscillator model. The present predicted results are compared to the experimental data and previous wake oscillator model results. Good agreement with experimental results is found.
基金supported by the National High Technology Research and Development Program of China (Grant N. 2006AA09A209-7)the Major Oil and Gas Program of China (Grant No. 2008ZX05026-04-011)+1 种基金Knowledge Innovative Program of the Chinese Academy of Sciences (Grant No. KJCX2-YW-L02)the National Natural Science Foundation of China (Grant No. 1077218)
文摘Thermally induced evolution of phase transformations is a basic physical-chemical process in the dissociation of gas hydrate in sediment (GHS). Heat transfer leads to the weakening of the bed soil and the simultaneous establishment of a time varying stress field accompanied by seepage of fluids and deformation of the soil. As a consequence, ground failure could occur causing engineering damage or/and environmental disaster. This paper presents a simplified analysis of the thermal process by assuming that thermal conduction can be decoupled from the flow and deformation process. It is further assumed that phase transformations take place instantaneously. Analytical and numerical results are given for several examples of simplified geometry. Experiments using Tetra-hydro-furan hydrate sediments were carried out in our laboratory to check the theory. By comparison, the theoretical, numerical and experimental results on the evolution of dissociation fronts and temperature in the sediment are found to be in good agreement.
基金supported by the National Basic Research Program of China ("973" Project) (Grant No. 2011CB711100)the National Hi-Tech Research and Development Program of China ("863" Project) (Grant No.2009BAQG12A03)Computing Facility for Computational Mechanics,Institute of Mechanics,Chinese Academy of Sciences
文摘With the speed upgrade of the high-speed train,the aerodynamic drag becomes one of the key factors to restrain the train speed and energy saving.In order to reduce the aerodynamic drag of train head,a new parametric approach called local shape function(LSF) was adopted based on the free form surface deformation(FFD) method and a new efficient optimization method based on the response surface method(RSM) of GA-GRNN.The optimization results show that the parametric method can control the large deformation with a few design parameters,and can ensure the deformation zones smoothness and smooth transition of different deformation regions.With the same sample points for training,GA-GRNN performs better than GRNN to get the global optimal solution.As an example,the aerodynamic drag for a simplified shape with head + one carriage + tail train is reduced by 8.7%.The proposed optimization method is efficient for the engineering design of high-speed train.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KJCX1-YW-21)
文摘The oil/water separation in a liquid-liquid cylindrical cyclone is experimentally studied in this article.The effects of the flow split-ratio and the flow rate on the oil/water separation performance are determined.From the experimental results,it is shown that with the increase of the flow split-ratio,the oil/water separation efficiency is enhanced at first,and an optimal flow split-ratio exists,beyond that optimal split-ratio,the watercut in the underflow keeps constant,while the oil content in the overflow begins to decrease.The process of the oil core structure formation and the phase distribution in the cyclone are determined by numerical simulations.Furthermore,the dependence of the separation efficiency on the Reynolds number and the flow split-ratio is investigated based on a dimensional analysis.A comparison between the predicted values and the experimental data shows a good agreement.
基金supported by the National Natural Science Foundation of China (Grant No. 10532070)the Knowledge Innovation Project of Chinese Academy of Sciences (Grant No. KJCX2-YW-L02)
文摘The initiation of pipeline spanning involves the coupling between the flow over the pipeline and the seepage-flow in the soil underneath the pipeline.The pipeline spanning initiation is experimentally observed and discussed in this article.It is qualitatively indicated that the pressure-drop induced soil seepage failure is the predominant cause for pipeline spanning initiation.A flow-pipe-seepage sequential coupling Finite Element Method（FEM） model is proposed to simulate the coupling between the water flow-field and the soil seepage-field.A critical hydraulic gradient is obtained for oblique seepage failure of the sand in the direction tangent to the pipe.Parametric study is performed to investigate the effects of inflow velocity,pipe embedment on the pressure-drop,and the effects of soil internal friction angle and pipe embedment-to-diameter ratio on the critical flow velocity for pipeline spanning initiation.It is indicated that the dimensionless critical flow velocity changes approximately linearly with the soil internal friction angle for the submarine pipeline partially-embedded in a sandy seabed.
基金supported by the National Key Technology R&D Program,Aerodynamic Optimization Design and Safe Evaluation Techniques on Chinese High-Speed Trains(Grant No.2009BAG12A03)the National Basic Research Program of China("973" Project)(Grant No.2011CB71100)
文摘The prediction of the pressure wave amplitude produced when two trains pass each other in the tunnel is important to the train design for airtightness and tunnel conditions in China.In this paper,the key factors of this problem were firstly stud-ied based on theoretical analysis.The equation of the worst tunnel length for the global maximum and minimum pressure values was derived.Then,the influence of tunnel length on global minimum pressure and the critical region in which the global minimum pressure varies rapidly were investigated.Finally,a numerical method based on two-dimensional Na-vier-Stokes equations was established.Typical conditions of two trains passing-by in tunnels of different lengths were simulated.The theoretical and computational results agree with each other closely.
