Study on the interaction of sedimenting cylindrical particles in still fluid

The sedimentations of two cylindrical particles in three different initial relative positions are numerically simulated using the lattice Boltzmann method. The movement characteristics and particle interactions during their sedimentation are presented and discussed in detail. The results show that, (i) if the two particles are released parallel but separated horizontally, they push away each other, rotate inwards and separate horizontally as they fall; (ii) if the two particles are released parallel but separated vertically, the sedimentation behavior can be classified into three stages: trailing, tumbling and separating; (iii) if the two particles are released perpendicular but separated vertically, the sedimentation behavior can be characterized as: trailing and rotating, touching and sliding. In order to validate our simulation, experiments were also conducted and the results agree well with the numerical ones. The project supported by the National Natural Science Foundation of China for Distinguished Scholars (19925210)     

Analytical and experimental modal analysis of nonuniformly ring-stiffened cylindrical shells

In this research, the free vibration analysis of cylindrical shells with circumferential stiffeners, i.e., rings with nonuniform stiffener eccentricity and unequal stiffener spacing, is investigated using analytical and experimental methods. The Ritz method is applied in analytical solution, while stiffeners are treated as discrete elements. The polynomial functions are used for Ritz functions. The effects of nonuniformity of stiffener distribution on natural frequencies are considered for free–free boundary conditions. Results show that, at constant stiffener mass, significant increments in natural frequencies can be achieved using nonuniform stiffener distribution. In experimental method, modal testing is performed to obtain modal parameters, including natural frequencies, mode shapes, and damping in each mode. Analytical results are compared with experimental ones, showing good agreement. Because of insufficient experimental modal data for nonuniform stiffener distribution, the results of modal testing obtained in this study could be a useful reference for validating the accuracy of other analytical and numerical methods for free vibration analysis.     

Analytical solution of radiation sound pressure of double cylindrical shells in fluid medium

ＩｎｔｒｏｄｕｃｔｉｏｎＳｏｕｎｄｒａｄｉａｔｉｏｎｆｒｏｍｔｈｅｄｏｕｂｌｅｓｈｅｌｌｓｗｈｉｃｈａｒｅｔｈｅｍａｉｎｓｔｒｕｃｔｕｒｅｏｆｓｕｂｍａｒｉｎｅｈｕｌｌｓｕｎｄｅｒｅｘｃｉｔａｔｉｏｎｉｎｆｌｕｉｄｍｅｄｉｕｍｉｓｖｅｒｙｉｍｐｏｒｔａｎｔｆｏｒｓｔｕｄｙｉｎｇｔｈｅｓｕｂｍａｒｉｎｅｈｉｄｉｎｇｔｅｃｈｎｏｌｏｇｙ .Ｆｏｒｔｈｅｖｉｂｒａｔｉｏｎｃｈａｒａｃｔｅｒｉｓｔｉｃｏｆｄｏｕｂｌｅｃｏｎｃｅｎｔｒｉｃｓｈｅｌｌｓ,ｉｔｈａｓｂｅｅｎｓｔｕｄｉｅｄｏｎｔｈｅｏｒｙａｎｄｅ…     

ANALYTICAL SOLUTION OF RADIATED SOUND PRESSURE OF RING－STIFFENED CYLINDRICAL SHELLS IN FLUID MEDIUM

ＡＮＡＬＹＴＩＣＡＬＳＯＬＵＴＩＯＮＯＦＲＡＤＩＡＴＥＤＳＯＵＮＤＰＲＥＳＳＵＲＥＯＦＲＩＮＧ－ＳＴＩＦＦＥＮＥＤＣＹＬＩＮＤＲＩＣＡＬＳＨＥＬＬＳＩＮＦＬＵＩＤＭＥＤＩＵＭＸｉｅＧｕａｎｍｏ（谢官员模）ＬｕｏＤｏｎｇｐｉｎｇ（骆东平）（Ｒｅｃｅｉｖ...     

Analytical solution to the problem of heat interaction of fluid flow and solid filling

The results of analytical solution to the problem of thermal interaction of a fluid stream with a media of solid particles found on the basis of the ODTPM model [1] are presented. A non-stationary behaviour of the volume-averaged temperature of solid filling, being a measure of the efficiency from heat transfer between fluid and solid phases, and of the heat-carrier temperature at the exit of the layer is studied. Time dependences computed according to the obtained relationships are in good agreement with the results of numerical calculations [1] for different sets of the problem parameters. The found solution expands the possibilities to analyze the efficiency of the “fluid-solid phase” systems and can be a basis to develop methods of experimental evaluation of different parameters of the system.     

Forced vibrations of coaxial reinforced cylindrical shells during interaction with a fluid

Rostov State University Scientific-Research Institute of Mechanics and Applied Mathematics, Rostovon-Don. Translated from Prikladnaya Mekhanika, Vol. 25, No. 12, pp. 63–68, December, 1989.     

薄膜结构流固耦合的CFD数值模拟研究

基于弱耦合分区求解策略,在CompaqVisualFortran6．5环境下搭建了薄膜结构三维流固耦合效应的CFD数值模拟平台。程序采用模块化编程思想,主要包含几何建模、流体分析、结构分析和数据交换四个模块。其中几何建模模块采用自行编制的膜结构找形分析程序,流体分析模块采用经过二次开发的计算流体力学软件FLUENT6．0,结构分析模块采用自行编制的膜结构动力分析程序MDLFX;在数据交换模块中,编制了基于薄板样条法的插值计算程序,以实现流固交界面上不同区域网格间的数据传递问题,编制了基于代数法和迭代法的动网格变形程序,以实现流固耦合运算中的动网格更新。基于该软件平台,对单向柔性屋盖和鞍形膜结构屋盖进行了流固耦合数值模拟,验证了方法的有效性。     

The spatial static and dynamic analysis of tall building structures

In this paper,the static and dynamic analyses of tall build-ings are studied as the space system by the application of“JIGFEX-II”programme.suggestions have been made for the cal-culation of earthquake forces and torques.Besides that,a prac-tical approach is proposed for realizing the analysis of com-plicated structures on minicomputers or on medium sized compu-ters.Reference data and charts from practical engineering ap-plications are also presented.     

Analytical modeling of fluid loaded orthogonally rib-stiffened sandwich structures: Sound transmission

An analytic model is developed to investigate the wave propagation and sound transmission characteristics of an infinite sandwich structure reinforced by two sets of orthogonal rib-stiffeners when subjected to convective fluid-loaded pressure. The rib-stiffeners are assumed to be identical and uniformly spaced, which can exert not only tensional forces and bending moments but also torsional moments on the facesheets. Inertial terms of the tensional forces, bending moments and torsional moments are introduced to account for inertial effects arising from the mass of the rib-stiffeners. With the surrounding acoustic fluids restricted by the acoustic wave equation, fluid-structure coupling is considered by imposing velocity continuity condition at fluid-panel interfaces. By applying the Bloch theorem for periodic structures, the structural and acoustic responses are expressed in a superposition form of space harmonics for a given wavenumber. The application of the virtual work principle for one periodic element yields two infinite sets of simultaneous algebraic coupled equations, which are numerically solved by truncating them in a finite range insofar as the solution converges. The validity and feasibility of the analytic model is qualified by comparing model predictions with existing results, in which the necessity and advantage of the exact modeling of rib-stiffener motions are also demonstrated. Specifically, the influences of inertial effects arising from rib-stiffener mass, the periodicity spacing of rib-stiffeners, and the airborne as well as structure-borne paths on the transmission of sound across the sandwich structure are quantified and conclusions of significant practical implications are drawn.     

复杂结构静力分析和屈曲分析程序系统DDJTJQ

ＤＤＪＴＪＱ是一个国内开发的复杂结构静力分析和屈曲分析有限元程序系统，自１９８６年通过技术鉴定以来又有了许多发展．本文着重介绍该程序系统的屈曲和后屈曲分析能力以及在不同工程领域结构分析中的应用．给出了几个大型复杂工程结构的计算结果．     

Finite element computations for unsteady fluid and elastic membrane interaction problems

The interaction between the hydrodynamic forces of a flow field and the elastic forces of adjacent deformable boundaries is described by elastohydrodynamics, a coupled fluid–elastic membrane problem. Direct numerical solution of the unsteady, highly non-linear equations requires that the dynamic evolution of both the flow field and the domain shape be determined as part of the solution, since neither is known a priori. This paper describes a numerical algorithm based on the deformable spatial domain space–time (DSD/ST) finite element method for the unsteady motion of an incompressible, viscous fluid with elastic membrane interaction. The unsteady Navier–Stoke and elastic membrane equations are solved separately using an iterative procedure by the GMRES technique with an incomplete lower-upper (ILU) decomposition at every time instant. One-dimensional, two-dimensional and deformable domain model problems are used to demonstrate the capabilities and accuracy of the present algorithm. Both steady state and transient problems are studied. © 1997 John Wiley & Sons, Ltd.     

The stability of a cylindrical elastic membrane of biological tissue and the effect of internal fluid flow

Summary Some stability problems for finitely deformed elastic membranes are considered. The first part treats the stability of a stretched elastic membrane which is orthotropic in its reference state. The stability criteria for a uniformly deformed orthotropic plane sheet under conditions of dead loading are obtained. The potential energy for a uniformly extended and inflated circular cylindrical membrane (the preferred directions being axial and circumferential) with axially symmetric deformations and under constant pressure is found to have the same form as that for an isotropic material. Stability criteria for a long tube are obtained and some numerical results are given through stability diagrams using strain energy functions appropriate for biological tissues. The effect on stability of the flow of an incompressible fluid through the tube is considered next. To model the internal fluid motion, small perturbations superimposed on a state of steady flow with velocity profiles of a slug flow and a Poiseuille flow are assumed, and a one-dimensional analysis is used as a third approach. Equations for the fundamental frequencies of vibration are derived. The fluid motion is found to have a stabilizing or destabilizing influence on the membrane depending on the approach used. The results are compared to Rayleigh’s results for a circular liquid jet and they are found to agree for the slug flow and the Poiseuille flow models.

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übersicht Es werden einige Stabilit?tsprobleme für Membranen mit endlichen Deformationen betrachtet. Im ersten Teil wird die Stabilit?t einer gedehnten Membran betrachtet, die im Ausgangszustand orthotrop ist. Es werden die Stabilit?tsbedingungen für ein gleichf?rmig deformiertes ebenes Blatt erhalten. Die potentielle Energie für eine gleichf?rmig gedehnte und aufgeblasene kreiszylindrische Membran mit achsialsymmetrischer Deformation unter konstantem Druck hat dann dieselbe Form wie bei isotropem Material. Es werden Stabilit?tskriterien für lange R?hren abgeleitet und einige numerische Ergebnisse für biologische Gewebe mitgeteilt. Als n?chstes wird der Einflu? auf die Stabilit?t der Str?mung eines inkompressiblen Fluids durch die R?hre untersucht. Dabei werden kleine St?rungen der station?ren Str?mung überlagert, wobei als Geschwindigkeitsprofil Schleichstr?mung und Poiseuille-Str?mung angenommen werden. Die eindimensionale Analyse wird bis zur dritten Ordnung durchgeführt. Es werden Gleichungen für die Frequenzen der Grundschwingungen abgeleitet. Dabei zeigt sich, da? die Fluidstr?mung je nach der Art der N?herungen einen stabilisierenden oder auch destabilisierenden Einflu? haben kann. Die Ergebnisse werden mit denen von Rayleigh für einen Fluidstrahl mit kreisf?rmigem Querschnitt verglichen. Dabei wird übereinstimmung sowohl für Schleich- wie auch für Poiseuille-Str?mung festgestellt.

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Dedicated to Hans Ziegler     

Unsteady interaction of a system of elastic cylindrical shells with a viscous compressible fluid

Dnepropetrovsk Institute of Railroad Transportation Engineers. Translated from Prikladnaya Mekhanika, Vol. 24, No. 1, pp. 30–37, January, 1988.     

张拉膜结构力密度法混合找形分析

论述了张拉膜结构力密度法混合找形的基本理论;所谓力密度法混合找形,即部分单元力密度控制,部分单元弹性控制;力密度控制采用线性求解,弹性控制采用非线性求解,通过迭代计算混合找形求出各结点的坐标值。据此编制了相应的计算软件;对工程实例进行了验算,结果表明,本文给出的计算结果与德国著名软件easy的计算结果相吻合。