Dynamics of body separation—analytical procedure

In this paper, an analytical procedure for the determination of the dynamic parameters of a remainder body after mass separation is developed. The method is based on the general principles of momentum and angular momentum of a body and system of bodies. The kinetic energy of motion of the whole body and also of the separated and remainder body is considered. The derivatives of kinetic energies with respect to the generalized velocity determine the velocity and angular velocity of the remainder body. To confirm the proposed procedure, the results are compared with those obtained using the method of momenta and angular momenta. In the paper, the theorem about increase of kinetic energies of the separated and remainder bodies for perfectly plastic separation is proved. The increase of the kinetic energies correspond to the relative velocities and angular velocities of the separated and remainder bodies. As an example, the mass separation from a pendulum is considered. The kinematic properties of the remainder pendulum are obtained using the analytic procedure. The results are in agreement with those obtained by applying the basic principles of Newton’s mechanics.     

VECTOR ANAYLYSIS OF SPATIAL MECHANISM——(IV)Dynamics of Spatial Mechanisms

The standard dynamical problems of the previous four spatial mechanisms are here solved by the method of vector equations.The procedure is completely independent of the transfer matrices due to the changes of reference frame from one connecting pair to the next, as used by Yang and Bagci[1][2].     

Dynamics of cavitation–structure interaction

Cavitation–structure interaction has become one of the major issues for most engineering applications. The present work reviews recent progress made toward developing experimental and numerical investigation for unsteady turbulent cavitating flow and cavitation–structure interaction. The goal of our overall efforts is to(1) summarize the progress made in the experimental and numerical modeling and approaches for unsteady cavitating flow and cavitation–structure interaction,(2) discuss the global multiphase structures for different cavitation regimes, with special emphasis on the unsteady development of cloud cavitation and corresponding cavitating flow-induced vibrations,with a high-speed visualization system and a structural vibration measurement system, as well as a simultaneous sampling system,(3) improve the understanding of the hydroelastic response in cavitating flows via combined physical and numerical analysis, with particular emphasis on the interaction between unsteady cavitation development and structural deformations. Issues including unsteady cavitating flow structures and cavitation–structure interaction mechanism are discussed.     

VECTOR ANALYSIS OF SPATIAL MECHANISM—(Ⅳ)Dynamics of Spatial Mechanisms

The standard dynamical problems of the previous four Spatialmechanisms are here solved by the method of vector equations.Theprocedure is completely independent of the transfer matrices dueto the changes of reference frame from one connecting pair to thenext,as used by Yang and Bagci.     

Dynamics of stochastic Lorenz–Stenflo system

This paper discusses the Lorenz–Stenflo system under the influence of L \(\acute{\hbox {e}}\) vy noise. We find conditions under which the solution to stochastic Lorenz–Stenflo system is exponentially stable. We then investigate the estimation of the global attractive set and stochastic bifurcation behavior of the stochastic Lorenz–Stenflo system. Results show that the jump noise can make the solution stable, the bounds and bifurcation to undergo change under some conditions. Numerical results show the effectiveness and advantage of our methods.     

《Stochastic Dynamics of Structures》评介

<正>现代科学理论、科学试验和计算技术的迅速发展极大地提高了人类认识自然、改造自然并与自然和谐相处的能力.在这一进程中,人们日益认识到:必须兼顾系统与环境中客观存在的各种随机要素,才能更准确地反映工程结构的动力响应和性态.这一客观需求,促进了结构随机动力学的深入研究与持续发展.     

Effects of Anisotropy and Drying Air Parameters on Drying of Deformable Porous Media Hydro-Dynamically and Thermally Anisotropic

The purpose of this work was to investigate numerically the drying of saturated deformable porous media. The considered sample is a rectangular porous plate which assumed to be both hydro-dynamically and thermally anisotropic, while the mechanical behavior of the sample is supposed to be isotropic. All walls of the plate are subjected to a convective heat flux. Moreover, the top and bottom walls are allowed the mass transfer. The Darcy–Brinkman extended model was used as the momentum balance equation for the liquid and solid phases. The energy balance equation is based on the local thermodynamic equilibrium assumption between the both phases. The lattice Boltzmann method is used to solve the governing differential equation system. A comprehensive analysis of the effect of anisotropy and the drying air parameters on macroscopic fields is investigated throughout this work.     

Dynamics of fine particles in liquid-solid fluidized beds

On the basis of the Local Equilibrium Model （LEM）, fine particles with large Richardson-Zaki exponent n show, under certain conditions during bed expansion and collapse, different dynamic behavior from particles with small n. For an expansion process there may be a concentration discontinuity propagating upward from the distributor, and, on the contrary, for a collapse process there may be a progressively broadening and upward-propagating continuous transition zone instead of discontinuity. The predictions of the bed height variation and the discontinuity trace have been validated experimentally.     

Dynamics of annular gas–liquid two-phase swirling jets

The dynamics of annular gas–liquid two-phase swirling jets have been examined by means of direct numerical simulation and proper orthogonal decomposition. An Eulerian approach with mixed-fluid treatment, combined with an adapted volume of fluid and a continuum surface force model, was used to describe the two-phase flow system. The unsteady, compressible, three-dimensional Navier–Stokes equations have been solved by using highly accurate numerical methods. Two computational cases have been performed to examine the effects of liquid-to-gas density ratio on the flow development. It was found that the higher density ratio case is more vortical with larger spatial distribution of the liquid, in agreement with linear theories. Proper orthogonal decomposition analysis revealed that more modes are of importance at the higher density ratio, indicating a more unstable flow field. In the lower density ratio case, both a central and a geometrical recirculation zone are captured while only one central recirculation zone is evident at the higher density ratio. The results also indicate the formation of a precessing vortex core at the high density ratio, indicating that the precessing vortex core development is dependent on the liquid-to-gas density ratio of the two-phase flow, apart from the swirl number alone.     

Variation principle of piezothermoelastic bodies, canonical equation and homogeneous equation

Combining the symplectic variations theory,the homogeneous control equa- tion and isoparametric element homogeneous formulations for piezothermoelastic hybrid laminates problems were deduced.Firstly,based on the generalized Hamilton variation principle,the non-homogeneous Hamilton canonical equation for piezothermoelastic bod- ies was derived.Then the symplectic relationship of variations in the thermal equilibrium formulations and gradient equations was considered,and the non-homogeneous canoni- cal equation was transformed to homogeneous control equation for solving independently the coupling problem of piezothermoelastic bodies by the inceusement of dimensions of the canonical equation.For the convenience of deriving Hamilton isoparametric element formulations with four nodes,one can consider the temperature gradient equation as constitutive relation and reconstruct new variation principle.The homogeneous equa- tion simplifies greatly the solution programs which are often performed to solve non- homogeneous equation and second order differential equation on the thermal equilibrium and gradient relationship.     

Some Results on Dynamics of Special Double-Loop ΣΔ-Modulators

The dynamic behaviour of a specific two-dimensional state space model with discontinuity is studied. This model arises from the study of double-loop -modulators with constant input. Using mathematical tools we explain certain simulation results, and some properties are derived. Simulations based on time-varying input are also provided.     

Homogenized elastic–viscoplastic behavior of anisotropic open-porous bodies with pore pressure

Constitutive modeling is studied for the homogenized elastic–viscoplastic behavior of pore-pressurized anisotropic open-porous bodies made of metallic base solids at small strains and rotations. For this purpose, by describing micro–macro relations relevant to periodic unit cells of anisotropic open-porous bodies subjected to pore pressure, constitutive features are discussed for the viscoplastic macrostrain rate in steady states. On the basis of the constitutive features found, the viscoplastic macrostrain rate is represented as an anisotropic function of Terzaghi’s effective stress, which is shown using Hill’s macrohomogeneity condition. The resulting viscoplastic equation is used to simulate the homogenized elastic–viscoplastic behavior of an ultrafine plate-fin structure subjected to uniaxial/biaxial loading in addition to pore pressure. The corresponding finite element homogenization analysis is also performed for comparison. It is demonstrated that the developed viscoplastic equation simulates well the anisotropic effect of pore pressure in the viscoplastic range in spite of there being no anisotropic factor and no fitting parameter in Terzaghi’s effective stress itself.     

Dynamics of worm-like micelles: the Cox–Merz rule

The viscoelastic behaviour of worm-like micelles in small-amplitude oscillatory, steady simple shear and uniaxial extensional flows are analyzed with a model that couples the Oldroyd-B constitutive equation with a kinetic equation that accounts for the structural changes induced by the flow. In some cases, the constitutive equation predicts a viscoelastic behaviour that is consistent with the Cox–Merz rule. Departures from this rule are also predicted. Experimental data obtained for two worm-like micellar systems indicate that in these solutions, the Cox–Merz rule is not usually followed, in agreement with the predictions of our model. In uniaxial extensional flow, the model predicts a strain hardening in the extensional viscosity at low extensional rates and a strain-thinning at high extensional rates.     

Leading-Order Dynamics of Gravity-Driven Flows in?Free-Standing Soap Films

We derive the leading-order equations that govern the dynamics of the flow in a falling, free-standing soap film. Starting with the incompressible Navier?CStokes equations, we carry out an asymptotic analysis using parameters that correspond to a common experimental setup. We account for the effects of inertia, surface elasticity, pressure, viscous stresses, gravity, and air drag. We find that the dynamics of the flow is dominated by the effects of inertia, surface elasticity, gravity, and air drag. We solve the leading-order equations to compute the steady-state profiles of velocity, thickness, and pressure in an experiment in which the film is in the Marangoni elasticity regime. The computational results, which include a Marangoni shock, are in good accord with the experimental measurements.     

Use of a one-parameter family of Gordon–Schowalter objective derivatives to describe finite strains of viscoelastic bodies

A constitutive relation is considered for viscoelastic materials at finite strains. This relation is obtained using a one-parameter family of Gordon–Schowalter objective derivatives and generalizes the elementary Maxwell model. It is shown that, in the problem of simple shear of an incompressible viscoelastic material, this constitutive relation allows one to obtain the Poynting effect for any parameters of the model.     

Two Problems of the Semi-Conductor Physics Discussed with the Point of View of the Fluid Dynamics

In this article,we discuss two problems of the semi-conductor physics from the point of view ofthe fluid dynamics.Firstly,we discuss the problem of the p-n junction,and find that the previoustreatment and the previous conclusion of the problem are somewhat erroneous.Secondly,we discussthe coefficient C of the block resistance,and find that the mathematical method of the previoustreatment is erroneous.