大型水平轴风轮转子／塔架耦合系统的气动弹性稳定性分析

建立了大型水平轴风轮转子／塔架耦合系统的气动弹性模型，推导了转子／塔架耦合系统周期系数运动方程，给出了气动弹性稳定性分析方法。对一风力机模型进行气动弹性稳定性计算，得到了与有关文献基本一致的结果。     

内燃机曲柄连杆机构运动动力学分析的柔性多体建模方法

提出了一个新的运行动力学模型，将连杆视为柔性体，将机构处理为由互相连接的刚体和柔体组成的多体系统，通过多刚体系分析及结构动力分析，得到多体系统的运动方程；将系统中的机械接点用一组依赖于耦合的参考坐标和弹性坐标的代数约束方程描述，并通过Ｌａｇｒａｎｇｅ乘子引入系统运动方程，得到一组由广义坐标及Ｌａｇｒａｎｇｅ乘子表示的混合微分／代数方程组。用Ｎｅｗｔｏｎ－Ｒａｐｈｓｏｎ及直接数字积分算法求解此混合方     

齿轮连接多平行轮系的扭转耦合振动分析

通过研究齿轮连接多平行轴系的扭转耦合振动，给出了齿轮副扭转耦合运动的约束条件，推导出齿轮连接多平行轴系的扭转耦合振动方程。以ＤＨＰ４５－１型压缩机中的齿轮连接轴系为例，分析和计算了齿轮连接多平行轴系的扭振特性。图７表３参４     

齿轮连接多平一系的扭砖耦合振动分析

通过研究齿轮连接多平行轴系的扭转耦合振动，给出了齿轮副扭转耦合运动的约束条件，推导出齿轮连接多平行轴系的扭转耦合振动方程。以ＤＨＰ４５－１型压缩机中的齿轮连接轴系为例，分析和计算了齿轮连接多行轴系的扭振特性。图７表３参４     

长管耦合水击控制的试验研究

对某水电站长2575m的压力管道系统采用耦合调频控制技术实施了水击控制试验，并有效地控制了水击压力峰值的增加，试验表明，在多种耦合因素的影响下压力波动沿程演化特性是系统状态的函数。在强扰动变频控制情况下，水击波动演化成波列，波列的群速度远小于相速度，动能和压力势能按群速度的速率转换，对管道安全有利，但对稳定运行不利。     

埋地原油管道停输期间温降及原油凝固传热模型及数值模拟

假设原油凝固区域为一固相和液相组成的动态多孔介质区域,建立了土壤、管道能量方程与原油质量、动量和能量方程相互耦合的传热模型,并对埋地原油管道停输温降过程进行了数值模拟.数值模拟结果能够合理解释停输期间温度场、凝固界面和自然对流规律.     

后弯管波力发电浮体模型试验研究

在造波水槽里，用4种新的后弯管波力发电浮体模型进行了试验研究，测定了它们的气室平均输出气流功率随波周期的变化曲线Na-To模型3－3为最佳浮体，波能转换效率提高达ηa=79.1%，测定了模型3－3和模型4－7的描泊力，给出了各自最大锚泊力随波高及随波周期的变化曲线Fmax-H0,Fmax-T0还用船模适航仪测定了模型3－3和4－7随波浪的运动状态。给出了浮体升沉，纵摇，纵荡随波周期的变化曲线Z／H0－T、a/H0-T,X/H0-T和Xmax/H0-T。     

非正交曲线系下数值模拟及PDA测量模化炉内湍流流场

构造强守恒形式N－S离散方程组，耦合求解速度和压力修正方程，κ-ε双方程模型模拟湍流粘性。在方程离散中，采用以加权平均方法计算胞元界面上不连续的几何因子，以保持坐标转换的光滑性；以迭代方式考虑交错压力梯度项，并对常规形式压力方程结果进行二次修正。计算结果表明，针对局部非光滑且远离正交性的炉内网格体系，上述特殊数值方法对保证求解精度和收敛性具有关键作用。采用3D－PDA（三维激光多谱勒固粒运动分析仪）对670t/h四角切圆炉的1：20模型内冷态流场进行了测量。数值模拟结果与实验结果基本吻合。     

两自由度直驱感应电机耦合效应分析和矢量控制建模

两自由度直驱感应电机轴端可以输出旋转运动、直线运动和螺旋运动。本文针对两自由度直驱感应电机的特殊结构与现象,建立耦合模型分析直线部分行波磁场对旋转运动的影响,修正了旋转部分转矩方程与直线部分推力方程。在两自由度直驱感应电机dq坐标系数学模型的基础上,建立该电机的转子磁场定向矢量控制模型,加入对直线部分与旋转部分耦合效应的动态补偿,在Matlab中搭建了该电机的矢量控制系统。仿真结果表明,旋转速度与直线速度能够快速跟踪给定速度,验证了考虑耦合效应动态补偿矢量控制模型的正确性。     

运动波方法及其在水文中的应用

近年来,运动波方法在水文界受到普遍重视和较多应用.运动波方法的基础是连续方程和阻力方程,二者都是水力学的基本方程.与水文中常用的推理公式和单位线等方法比较,运动波方法物理概念明确,且方程本身是非线性的,描述洪流演进时就不必再用经验方法作非线性改正.在一般条件下,运动波方程的求解要采用数值方法,而曾使其应用受到限制.随着计算机的发展,这一困难已基本克服.一些著名水文学家认为,水文学将迈出的一步是运动波方法,这种方法已发展成熟,可用于许多水文问题.目前,微型计算机已在我国普及,应用运动波方法具备了条件.本文拟简要介绍运动波方法的原理及应用,供参考.     

A new finite element formulation based on the velocity of flow for water hammer problems

The primary objective of this paper is to develop a simulation model for the fluid–structure interactions (FSI) that occur in pipeline systems mainly due to transient events such as rapid valve closing. The mathematical formulation is based on waterhammer equations, traditionally used in the literature, coupled with a standard beam formulation for the structure. A new finite element formulation, based on flow velocity, has been developed to deal with the valve closure transient excitation problems. It is shown that depending on the relative time-scales associated with the structure, fluid and excitation forces, there are situations where the structural vibration response increases with FSIs. This is in contrast to what is normally accepted in the literature, i.e. FSI reduces the structural displacements.     

直接水击的计算公式

根据阀门逐渐关闭时产生三角形水击起始波的假定，推导出直接水击压强的计算公式；从而得到当压力管道发生直接水击时，存在一个水击压强的最大值，并给出其解；还得出水击波速与阀门关闭方式无关．     

Fluid–structure interaction analysis of flow and heat transfer characteristics around a flexible microcantilever in a fluidic cell

This investigation focuses on studying the effect of flow conditions and the geometric variation of the microcantilever's bluff body on the microcantilever detection capabilities within a fluidic device using a finite element fluid–structure interaction model. Such parameters include inlet velocity, flow direction, and height of the microcantilever's supporting system within the fluidic cell. The transport equations are solved using a finite element formulation based on the Galerkin method of weighted residuals. For a flexible microcantilever, a fully coupled fluid–structure interaction (FSI) analysis is utilized and the fluid domain is described by an Arbitrary–Lagrangian–Eulerian (ALE) formulation that is fully coupled to the structure domain. The results of this study showed a profound effect of the magnitude and direction of the inlet velocity and the height of the bluff body on the deflection of the microcantilever. The vibration characteristics were also investigated in this study. This work paves the road for researchers to design efficient microcantilevers that display least errors in the measurements.     

Ram‐air kite airfoil and reinforcements optimization for airborne wind energy applications

We present a multidisciplinary design optimization method for the profile and structural reinforcement layout of a ram‐air kite rib. The aim is to minimize the structural elastic energy and to maximize the traction power of a ram‐air kite used for airborne wind energy generation. Because of the large deformations occurring during flight, a fluid‐structure interaction (FSI) routine is included in the optimization, which determines the actual deformed rib geometry and its corresponding aerodynamic characteristics. A qualitative comparison between FSI inclusion and exclusion in the optimization is given. Discrepancies in airfoil profile and structural layout are observed.     

Unsteady flow and mass transfer in models of stenotic arteries considering fluid-structure interaction

In this work the unsteady non-Newtonian blood flow and mass transfer in symmetric and non-symmetric stenotic arteries are numerically simulated considering the fluid-structure interaction (FSI) using the code ADINA. Blood with hyperviscosity syndrome is considered and hyperelastic Mooney–Rivlin model is used for the compliant arterial wall. The inlet boundary condition of imposed velocity or pressure is critical to obtain realistic hemodynamic results in stenotic arteries. The FSI affects significantly the hemodynamics on the stenotic arteries models, the arteries are considerably dilated and compressed due the stenosis. The stenosis severity and geometry have important influence on recirculation length, and distribution of concentration of macromolecules, such as low density lipoproteins (LDL).     

Bluff body with built-in piezoelectric cantilever for flow-induced energy harvesting

This paper investigates a flow-induced vibration energy harvester comprising a piezoelectric beam (piezo-beam) installed within a hollow circular cylinder. Under the flow excitation, the energy-harvesting system including the cylinder and the piezo-beam vibrates and generates electricity. A lumped parametric model incorporating the fluid-structure interaction (FSI) is developed to evaluate the performance of the proposed energy harvester. Based on the theoretical analysis, several guidelines on the design and optimization of the proposed energy harvester are provided. Subsequently, a numerical model is used to simulate the FSI between the proposed system and the external flow field. Finally, a physical prototype is fabricated and an experiment is conducted to test the actual performance for validation. The theoretical analysis results are verified by the numerical and experimental results.     

Ionic liquid electrolytes compatible with graphitized carbon negative without additive and their effects on interfacial properties

Introduction of bis(fluorosulfonyl)imide (FSI) as an anion to an ambient-temperature ionic liquid electrolyte based on 1-ethyl-3-methylimidazolium (EMI) as well as lithium (Li) cations can provide a reversible Li intercalation into a graphitized electrode, while such intercalation is completely irreversible without FSI. The surface-layer components on the graphitized electrodes, cycled in the ionic liquid electrolytes with and without FSI, were found to be chemically similar based on X-ray photoelectron spectroscopy. Ac impedance spectroscopy revealed that the resistance of the electrode charged with FSI was much lower even than that charged in a solvent electrolyte system containing ethylene carbonate (EC) and dimethyl carbonate (DMC). On the basis of these physicochemical analyses, the origins of cycleability in the presence of FSI are discussed.     

Preconditioned Conjugate Gradient and Multigrid Methods for Numerical Solution of Multicomponent Mass Transfer Equations II. Convection-Diffusion-Reaction Equations

This work continues our previous analysis concerning the performances of the nonlinear multigrid (the Full Approximation Storage algorithm) method and modified Picard preconditioned conjugate gradient methods for the numerical solution of the two-dimensional, steady-state, multicomponent mass transfer equations. The present test problems are steady-state, linear and nonlinear, convection-diffusion-reaction equations. The upwind finite difference method was used to discretize the mathematical model equations. The numerical results obtained show good numerical performances.     

Numerical simulation of drop deformation and breakup in shear flow

Three‐dimensional numerical simulation of the deformation and breakup of an isolated liquid drop suspended in immiscible viscous fluid under shear flow was performed with diffuse interface method. The governing equations of the model were described by Navier– Stokes– Cahn– Hilliard equations. The surface tension was treated as a modified stress. In this paper, a uniform staggered Cartesian grid was used. The transient Navier– Stokes equations were solved by an approximation projection method based on pressure increment formulation, while the Cahn– Hilliard equations were solved by a nonlinear full approximation multigrid method. The numerical results of the drop deformation and breakup were in good agreement with the experimental measurements. Therefore, the present model could be perfectly applied to study the mechanism of drop deformation and breakup. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 286– 294, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20160