The dynamic buckling of elasto-plastic cylindrical shells under axial fluid-solid impact is investigated theoretically. A simplified liquid- gas- structure model is given to approximately imitate the problem. The basi...The dynamic buckling of elasto-plastic cylindrical shells under axial fluid-solid impact is investigated theoretically. A simplified liquid- gas- structure model is given to approximately imitate the problem. The basic equation of the structure is derived from a minimum principle in dynamics of elasto-plastic continua at finite deformation, and the flow theory of plasticity is employed. The liquid is incompressible and the gas is compressed adiabatically. A number of numerical results are presented and the characteristics of the buckling behavior under fluid-solid impact are illustrated.展开更多
This paper presents a review of the work on fluid/structure impact based on inviscid and imcompressible liquid and irrotational flow. The focus is on the velocity potential theory together with boundary element method...This paper presents a review of the work on fluid/structure impact based on inviscid and imcompressible liquid and irrotational flow. The focus is on the velocity potential theory together with boundary element method （BEM）. Fully nonlinear boundary conditions are imposed on the unknown free surface and the wetted surface of the moving body. The review includes （1） vertical and oblique water entry of a body at constant or a prescribed varying speed, as well as free fall motion, （2） liquid droplets or column impact as well as wave impact on a body, （3） similarity solution of an expanding body. It covers two dimensional （2D）, axisymmetric and three dimensional （3D） cases. Key techniques used in the numerical simulation are outlined, including mesh generation on the multivalued free surface, the stretched coordinate system for expanding domain, the auxiliary function method for decoupling the mutual dependence of the pressure and the body motion, and treatment for the jet or the thin liquid film developed during impact.展开更多
Fluid percussion-induced traumatic brain injury models have been widely used in experimental research for years. In an experiment, the stability of impaction is inevitably affected by factors such as the appearance of...Fluid percussion-induced traumatic brain injury models have been widely used in experimental research for years. In an experiment, the stability of impaction is inevitably affected by factors such as the appearance of liquid spikes. Management of impact pressure is a crucial factor that determines the stability of these models, and direction of impact control is another basic element. To improve experimental stability, we calculated a pressure curve by generating repeated impacts using a fluid percussion device at different pendulum angles. A stereotactic frame was used to control the direction of impact. We produced stable and reproducible models, including mild, moderate, and severe traumatic brain injury, using the MODEL01-B device at pendulum angles of 6°, 11° and 13°, with corresponding impact force values of 1.0 ± 0.11 atm（101.32 ± 11.16 k Pa）, 2.6 ± 0.16 atm（263.44 ± 16.21 k Pa）, and 3.6 ± 0.16 atm（364.77 ± 16.21 k Pa）, respectively. Behavioral tests, hematoxylin-eosin staining, and magnetic resonance imaging revealed that models for different degrees of injury were consistent with the clinical properties of mild, moderate, and severe craniocerebral injuries. Using this method, we established fluid percussion models for different degrees of injury and stabilized pathological features based on precise power and direction control.展开更多
As a further development of the authors' work (Huang and Qian, 1993), in this paper a new numerical method based on the time domain boundary element technique is proposed for solving fluid-solid coupling problems,...As a further development of the authors' work (Huang and Qian, 1993), in this paper a new numerical method based on the time domain boundary element technique is proposed for solving fluid-solid coupling problems, in which a rigid body impacts normally on the calm surface of a half-space fluid. A fundamental solution to the half-space potential flow problem is first derived with the method of images. Then, an equivalent boundary integral equation in the Laplace transform domain is established by means of Green's second identity. Through the inverse Laplace transform and discretization in both time and boundary of the fluid region, the numerical calculation for the problem under consideration has been carried out. Several examples demonstrate that the present method is more efficient than existing ones, from which it is also seen that the shape of the impacting body has a considerable effect on the total impact force.展开更多
A simple solution of the dynamic buckling of stiffened plates under fluid-solid impact loading is presented.Based on large deflection theory,a discretely stiffened plate model has been used.The tangential stresses of ...A simple solution of the dynamic buckling of stiffened plates under fluid-solid impact loading is presented.Based on large deflection theory,a discretely stiffened plate model has been used.The tangential stresses of stiffeners and in-plane displacement are neglected.Applying the (Hamilton's) principle,the motion equations of stiffened plates are obtained.The deflection of the plate is taken as Fourier series,and using Galerkin method,the discrete equations can be deduced,which can be solved easily by Runge-Kutta method.The dynamic buckling loads of the stiffened plates are obtained from Budiansky-Roth(B-R) curves.展开更多
Based on linearized 2-D Navier-Stokes equation, a Laplacetransform-boundary element coupling method for viscousfluid-structure impact analysis is proposed. Under assumption ofincompressibility for the fluid, the corre...Based on linearized 2-D Navier-Stokes equation, a Laplacetransform-boundary element coupling method for viscousfluid-structure impact analysis is proposed. Under assumption ofincompressibility for the fluid, the corresponding equivalentboundary integral equation in terms of the potential function andstream function is first established by Lamb's transform in theLaplace transform domain.展开更多
泥石流是我国西南山区常见的地质灾害。架空输电杆塔在泥石流的冲击下往往发生基础破坏甚至会造成杆塔倒塌。首先采用光滑粒子流体动力学(smoothed particle hydrodynamics,简称SPH)方法和有限元方法(finite element method,简称FEM)相...泥石流是我国西南山区常见的地质灾害。架空输电杆塔在泥石流的冲击下往往发生基础破坏甚至会造成杆塔倒塌。首先采用光滑粒子流体动力学(smoothed particle hydrodynamics,简称SPH)方法和有限元方法(finite element method,简称FEM)相耦合的三维数值方法模拟了泥石流对杆塔基础的冲击作用;在与相关模型试验结果验证的基础上,开展了不同泥石流密度、黏度系数及初始速度条件下对输电塔基础的冲击力作用的参数分析;研究结果表明:随着泥石流初始速度的增加,冲击力峰值会随之增大;前排基础的冲击力峰值均大于后排基础;泥石流冲击过程特性受到泥石流密度和黏度系数影响。与稀性泥石流相比:黏性泥石流冲击基础后,基础下游真空区相对要小;此外,将数值模拟结果与Kwan冲击力公式及铁二院推荐的冲击压力设计公式预测值进行对比分析可以发现:Kwan冲击力公式能较好地预测出基础所受泥石流冲击力的平均趋势,最大预测误差低于30%,铁二院公式预测的稀性和黏性泥石流的冲击压力平均偏低分别约17%和28%。相关研究结果有望为泥石流频发区域输电塔基础的设计和风险评估提供一定的参考依据。展开更多
文摘The dynamic buckling of elasto-plastic cylindrical shells under axial fluid-solid impact is investigated theoretically. A simplified liquid- gas- structure model is given to approximately imitate the problem. The basic equation of the structure is derived from a minimum principle in dynamics of elasto-plastic continua at finite deformation, and the flow theory of plasticity is employed. The liquid is incompressible and the gas is compressed adiabatically. A number of numerical results are presented and the characteristics of the buckling behavior under fluid-solid impact are illustrated.
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant Nos. 11302057, 11302056）, the Fundamental Research Funds for the Central Universities （Grant No. HEUCF140115） and the Research Funds for State Key Laboratory of Ocean Engineering in Shanghai Jiao Tong University （Grant No. 1310）.
文摘This paper presents a review of the work on fluid/structure impact based on inviscid and imcompressible liquid and irrotational flow. The focus is on the velocity potential theory together with boundary element method （BEM）. Fully nonlinear boundary conditions are imposed on the unknown free surface and the wetted surface of the moving body. The review includes （1） vertical and oblique water entry of a body at constant or a prescribed varying speed, as well as free fall motion, （2） liquid droplets or column impact as well as wave impact on a body, （3） similarity solution of an expanding body. It covers two dimensional （2D）, axisymmetric and three dimensional （3D） cases. Key techniques used in the numerical simulation are outlined, including mesh generation on the multivalued free surface, the stretched coordinate system for expanding domain, the auxiliary function method for decoupling the mutual dependence of the pressure and the body motion, and treatment for the jet or the thin liquid film developed during impact.
基金supported by a grant from the International S cience and Technology Cooperation Projects of China,No.2011DFG33430
文摘Fluid percussion-induced traumatic brain injury models have been widely used in experimental research for years. In an experiment, the stability of impaction is inevitably affected by factors such as the appearance of liquid spikes. Management of impact pressure is a crucial factor that determines the stability of these models, and direction of impact control is another basic element. To improve experimental stability, we calculated a pressure curve by generating repeated impacts using a fluid percussion device at different pendulum angles. A stereotactic frame was used to control the direction of impact. We produced stable and reproducible models, including mild, moderate, and severe traumatic brain injury, using the MODEL01-B device at pendulum angles of 6°, 11° and 13°, with corresponding impact force values of 1.0 ± 0.11 atm（101.32 ± 11.16 k Pa）, 2.6 ± 0.16 atm（263.44 ± 16.21 k Pa）, and 3.6 ± 0.16 atm（364.77 ± 16.21 k Pa）, respectively. Behavioral tests, hematoxylin-eosin staining, and magnetic resonance imaging revealed that models for different degrees of injury were consistent with the clinical properties of mild, moderate, and severe craniocerebral injuries. Using this method, we established fluid percussion models for different degrees of injury and stabilized pathological features based on precise power and direction control.
基金National Defence Foundation of Science & Technology of China,Grant No.J14.8.1JW05National Key Project of China(No.PD9521907)
文摘As a further development of the authors' work (Huang and Qian, 1993), in this paper a new numerical method based on the time domain boundary element technique is proposed for solving fluid-solid coupling problems, in which a rigid body impacts normally on the calm surface of a half-space fluid. A fundamental solution to the half-space potential flow problem is first derived with the method of images. Then, an equivalent boundary integral equation in the Laplace transform domain is established by means of Green's second identity. Through the inverse Laplace transform and discretization in both time and boundary of the fluid region, the numerical calculation for the problem under consideration has been carried out. Several examples demonstrate that the present method is more efficient than existing ones, from which it is also seen that the shape of the impacting body has a considerable effect on the total impact force.
文摘A simple solution of the dynamic buckling of stiffened plates under fluid-solid impact loading is presented.Based on large deflection theory,a discretely stiffened plate model has been used.The tangential stresses of stiffeners and in-plane displacement are neglected.Applying the (Hamilton's) principle,the motion equations of stiffened plates are obtained.The deflection of the plate is taken as Fourier series,and using Galerkin method,the discrete equations can be deduced,which can be solved easily by Runge-Kutta method.The dynamic buckling loads of the stiffened plates are obtained from Budiansky-Roth(B-R) curves.
基金the National Defence Foundation of Science & Technology of China (No.J14.8.1.JW0515)
文摘Based on linearized 2-D Navier-Stokes equation, a Laplacetransform-boundary element coupling method for viscousfluid-structure impact analysis is proposed. Under assumption ofincompressibility for the fluid, the corresponding equivalentboundary integral equation in terms of the potential function andstream function is first established by Lamb's transform in theLaplace transform domain.
文摘泥石流是我国西南山区常见的地质灾害。架空输电杆塔在泥石流的冲击下往往发生基础破坏甚至会造成杆塔倒塌。首先采用光滑粒子流体动力学(smoothed particle hydrodynamics,简称SPH)方法和有限元方法(finite element method,简称FEM)相耦合的三维数值方法模拟了泥石流对杆塔基础的冲击作用;在与相关模型试验结果验证的基础上,开展了不同泥石流密度、黏度系数及初始速度条件下对输电塔基础的冲击力作用的参数分析;研究结果表明:随着泥石流初始速度的增加,冲击力峰值会随之增大;前排基础的冲击力峰值均大于后排基础;泥石流冲击过程特性受到泥石流密度和黏度系数影响。与稀性泥石流相比:黏性泥石流冲击基础后,基础下游真空区相对要小;此外,将数值模拟结果与Kwan冲击力公式及铁二院推荐的冲击压力设计公式预测值进行对比分析可以发现:Kwan冲击力公式能较好地预测出基础所受泥石流冲击力的平均趋势,最大预测误差低于30%,铁二院公式预测的稀性和黏性泥石流的冲击压力平均偏低分别约17%和28%。相关研究结果有望为泥石流频发区域输电塔基础的设计和风险评估提供一定的参考依据。
