旋风分离器压力损失及减阻杆的研究

本文介绍通过安装旋风分离器减阻杆前后压力损失及分离效率的测定，了解减阻杆对分离器性能的影响．根据流场测定结果，分析了减阻杆的减阻机理及减阻杆减阻时可保证分离效率的原因．     

旋风分离器减阻杆结构及减阻前后流场的测定与分析

报告了在旋风分离器内安装不同断面形状及尺寸的细杆（简称减阻杆）后对流动阻力降低及安装减阻杆前后旋风分离器内流场变化的测定结果，得出了减阻幅度与减阻杆插入长度和迎风面积及背风面曲率半径成正比、减阻杆使切向速度及轴向速度梯度减小、径向上静压梯度减小和轴向上逆压梯度减小等结论．本文同时对减阻杆的减阻机理及减阻时保证分离效率或提高分离效率的原因进行了分析．     

水下减阻技术研究综述

在简要回顾早期减阻研究的基础上,对现有典型水下湍流减阻技术进行了较深入地分析.重点介绍了脊状表面减阻、微气泡减阻和疏水/超疏水表面减阻的研究现状.分别从实验研究和理论研究两方面对其进行了阐述,并着重强调了各自的减阻机理. 此外,还简要介绍了柔顺壁面减阻、壁面振动减阻等其它减阻技术.展望了水下减阻技术今后的研究重点及其应用前景.      

等离子体减阻技术的研究进展

利用等离子体的特性减小飞行器的气动阻力是一种新概念的减阻思路.目前国外的一些风洞实验和计算结果已证明了等离子体减阻效果的显著性.本文介绍了国外等离子体减阻技术的研究进展,包括:逆向等离子体喷流减阻、基于等离子体边界层控制减阻和局部施加能量点源减阻.分析了等离子体减阻的基本原理及所涉及的一些关键技术点.最后针对我国的减阻研究情况,提出了等离子体减阻技术的研究方向.      

水下湍流减阻途径分析

综述了壁湍流边界层分层结构及近壁区湍流猝发过程,对现有典型水下湍流减阻技术进行了较深入地总结.根据各类减阻方法的特点对水下湍流减阻方法进行了分类,并分析了各类减阻方法对壁湍流流场的影响特征,总结了维持或延长层流、干扰湍流"猝发"、壁面隔离、增大湍流阻尼和改变壁面物性等5种水下湍流减阻可行途径,为开展水下湍流减阻研究及发现新的减阻方法提供参考.     

大型运输机的减阻技术

回顾了到目前为止可能用在大型飞机上的相关减阻技术,从三个方面(减小摩擦阻力、降低诱导阻力、减小激波阻力)详细介绍了多种减阻技术的方法和原理.其中减小摩擦阻力分成层流减阻和湍流减阻两个部分.层流减阻中吸气控制方法、湍流减阻中沟槽壁面控制方法、翼梢小翼技术、激波鼓包技术等都有可能成为改进新一代大型运输机阻力特性的实用技术.粗糙阵列、等离子体激励器、动态控制三维鼓包等新技术也为减阻技术的实际应用提供了新的可能性.     

DRAG REDUCTION TECHNIQUE FOR LARGE TRANSPORT AIRCRAFT

回顾了到目前为止可能用在大型飞机上的相关减阻技术,从三个方面(减小摩擦阻力、降低诱导阻力、减小激波阻力)详细介绍了多种减阻技术的方法和原理. 其中减小摩擦阻力分成层流减阻和湍流减阻两个部分. 层流减阻中吸气控制方法、湍流减阻中沟槽壁面控制方法、翼梢小翼技术、激波鼓包技术等都有可能成为改进新一代大型运输机阻力特性的实用技术. 粗糙阵列、等离子体激励器、动态控制三维鼓包等新技术也为减阻技术的实际应用提供了新的可能性.     

重型货车仿生气动减阻装置的优化设计

为了优化某重型货车的空气阻力系数,设计了针对大型货车整体的顶部仿生、底部、尾部、侧裙等4种减阻装置。采用计算流体动力学分析方法研究了4种减阻装置主要结构参数对气动阻力的影响。在此基础上采用正交试验法对4种气动减阻装置的主要参数进行了优化,获得了最优减阻效果货车模型。研究结果表明:在4种减阻装置中,顶部仿生减阻装置的弧形高度对货车空气阻力系数的影响最大,侧裙高度的影响最小;获得的最优货车模型的空气阻力系数为0.6218,相对于货车原始模型的减阻率为20.46%;受海豚头部形态启发设计的仿生导流罩具有明显的减阻效果,复合减阻模型的空气阻力系数为0.5655,相对于最优货车模型的减阻率为9.900%,相对于货车原始模型的减阻率达到了27.70%。该研究结果可为重型货车的优化设计提供重要参考。     

逆向喷流流场模态分析及减阻特性研究

逆向喷流减阻的基本原理是利用逆向高速喷流与飞行器绕流的相互作用，使飞行器周围的流场结构发生变化，致使飞行器的气动特性发生改变，从而改善飞行器的气动性能。利用数值模拟方法对轴对称球头、截锥的逆向喷流流场开展了研究，考虑了高温非平衡化学反应对流场的影响。模拟了球头和截锥在不同总压比时流场不同的模态：长穿透流模态（LPM）和短穿透流模态（SPM），得到了不同模态下钝体表面压力、气动力系数和不同模态之间转换的瞬态效应．简单分析了喷流在减阻方面的应用，给出了几个喷口参数与减阻效率之间的关系，提出了喷流减阻工程应用时应考虑的主要因素。     

海洋减阻技术的研究现状

船舶、舰艇、鱼雷等海中航行体在海洋经济建设和海洋国防中发挥着重要作用.海中航行体的运行速度和能量消耗率是评价其性能的重要指标.利用减阻技术降低航行体在海水中的行驶阻力具有重要意义.按减阻机理对现今重要的海洋减阻技术进行分类和总结,并详细介绍其研究现状和减阻机理,主要包括仿生减阻、微气泡减阻和疏水/超疏水涂层减阻.通过对现有海洋减阻技术的总结和分析,展望了其今后的研究重点.     

正交各向异性厚板的边界元解法

本文利用 Hormander 算子法和平面波分解法导出了计入剪切变形的正交各向异性厚板的基本解。建立了计入剪切变形的正交各向异性厚板的边界积分方程。文中详细地讨论了基本解的数值计算,并用边界元法分析了一些算例。     

Microstructure in a Cubic to Orthorhombic Transition

Microstructures for a cubic to orthorhombic transition are constructed using a geometrically nonlinear, thermoelastic theory of martensitic transformations. Such microstructures are of interest because they provide low energy paths along which a specimen can transform. The particular microstructures considered are the twinned martensite, austenite–martensite, wedge, triangle, and diamond. More specifically, all possible twins are found along with the corresponding twinning elements and magnitude of the twin shear. Further, two kinds of austenite–martensite microstructures are studied: those with a single variant of martensite and those with twinned martensite. The regions in the space of transformation stretches in which each of these microstructures exist are determined, and the shape strains and habit plane normals are found as well. In addition, special microstructures, the wedge, triangle, and diamond, are constructed with both the austenite-single variant and austenite-twinned martensite microstructures. These special microstructures are of interest because they provide a mechanism through which the transformation may proceed more easily, and they are possible only in alloys with particular transformation stretches. Numerically computed level curves in the space of the stretches are presented on which the special microstructures are possible. These results may be useful in providing guidelines for alloy design.     

Simulation of spatial multibody systems with friction

A formulation for modeling and simulation of friction effects in spatial multibody systems is presented. Constraint reaction forces on rigid bodies that are connected by joints that support friction are derived as functions of Lagrange multipliers, using D’Alembert’s principle. Friction forces acting on bodies are calculated as a function of joint geometry, constraint reaction forces that are functions of Lagrange multipliers, and relative velocities at constraint contact points that are determined by system kinematics. Friction forces are implemented in index 0 differential-algebraic equations of motion that are solved numerically using explicit and implicit numerical integration methods. Spatial examples are presented, yielding accurate results and demonstrating that the systems are not stiff, even in the presence of friction and stiction.     

Approximate symmetries of creeping flow equations of a second grade fluid

Creeping flow equations of a second grade fluid are considered. Two current approximate symmetry methods and a modified new one are applied to the equations of motion. Approximate symmetries obtained by different methods and the exact symmetries are contrasted. Approximate solutions corresponding to the approximate symmetries are derived for each method. Symmetries and solutions are compared and advantages and disadvantages of each method are discussed in detail.     

Exact solution to peristaltic transport of power-law fluid in asymmetric channel with compliant walls

Effects of compliant wall properties on the peristaltic flow of a non-Newtonian fluid in an asymmetric channel are investigated.The rheological characteristics are characterized by the constitutive equations of a power-law fluid.Long wavelength and low Reynolds number approximations are adopted in the presentation of mathematical developments.Exact solutions are established for the stream function and velocity.The streamlines pattern and trapping are given due attention.Salient features of the key parameters entering into the present flow are displayed and important conclusions are pointed out.     

Mesh effects on the computation of non-linear gravity waves of arbitrary discharge

Numerical computations of non-linear gravity waves are presented and the effects of mesh variations on the results are discussed. Waves are regarded as two-parameter families (λ,A)_Q of arbitrary discharge Q, and computations are carried out using a new Kantorovich algorithm. Mesh effects are to a large extent dependent on the particular wave region under consideration. Three such regions are identified and typical examples are computed and discussed.     

Method of molecular dynamics in mechanics of deformable solids

The basic principles of the method of molecular dynamics are analyzed. Symplectic difference schemes for the numerical solution of molecular dynamics equations are considered. Stability is studied, and the errors in the energy conservation law, which are induced by using these schemes, are estimated. Equations of mechanics of continuous media are derived by means of averaging over the volume of an atomic system. Expressions for the stress tensor are obtained by using the virial principle and the method of averaging over the volume. The principles of construction of EAM and MEAM potentials of atomic interaction in crystals are analyzed. Two problems of fracture of copper-molybdenum composites are solved by the method of molecular dynamics.     

根部柔性梁的不确定性建模与确认

首先导出了包含根部挠性参数的悬臂梁动力学方程近似解,将平动和转动柔性参数作为不确定性源,根据若干预紧力矩下的模态实验结果完成了柔性参数识别,并假定其服从正态随机分布,识别了均值与标准差,进而通过回归分析建立了不确定参数随预紧力矩变化的数学模型.最后通过新的模态实验结果对所建模型进行了确认,通过确认结果,明确了该模型的使用范围.     

Analytical and numerical solutions of electro-osmotically driven flow of a third grade fluid between micro-parallel plates

Electro-osmotic flow of a third grade fluid between micro-parallel plates is considered. The equations of motion are derived and made dimensionless. Approximate analytical solutions are obtained by perturbation techniques. Constant viscosity and temperature dependent viscosity (Reynolds model) cases are treated separately. Numerical solutions of the equations are also obtained. Influences of non-Newtonian parameter, Joule heating effect, viscosity index and electro-kinetic effect on the velocity and temperature profiles are shown. Approximate and numerical solutions are contrasted.