流体力学新进展——————第五届国际流体力学会议概况

介绍了第五届国际流体力学会议(Proceedings of the 5thInternational Conference on Fluid Mechanics, 2007年8月15$\sim$19日, 上海)的基本情况.大会报告涉及生物流体力学、湍流与流动控制、超声速流动、超空泡减阻、破碎波与海岸泥沙输运等当前流体力学前沿领域的研究进展;按流体力学学科分支总结了本次会议分会场交流论文的基本情况,阐述了若干学科分支方向的研究进展.      

一种寻求层状流动新解的方法

复杂层状流动是流体力学中的一类典型的流动。一般而言，流体力学中有两种特殊的流动：一种是Beltrami流动，另一种就是层状流动。对于前者，已经讨论过很多；但是后者的精确解却很难获得，这是因为很难解这种流动的Navier-Stokes方程或Euler方程。从不可压缩条件出发，如果让速度的形式满足一些特殊的条件，可以得到关于这种流动的某些新的精确解，例如发现一种间歇流精确解。     

HPAM溶液在石英微圆管中的流动实验

针对HPAM溶液在油藏孔隙中的复杂渗流特性问题,在内径为10～350μm微圆管中进行了部分水解聚丙烯酰胺(HPAM)溶液的流动实验.实验结果表明:在本文实验条件下,HAPM溶液在管径尺度较小的微圆管内的流动规律明显偏离常规尺度下的非牛顿流体力学流动规律,其截面平均流速高于按照常规尺度流动推算出的结果,且管径越小,偏离程度越大,微尺度效应越强.     

不可压平面无黏流动的弹性力学比拟

构造了一个特殊的弹性力学平面问题比拟不可压平面无黏流动, 从而使这类流体力学问题可 以采用固体力学软件ANSYS计算. 算例说明了比拟关系的正确性, 同时说明这样的比拟计算 与直接使用流体力学软件Fluent计算相比, 可以得到更精确的结果.     

微流控器件中的多相流动

微流控技术及微流控器件是近年来发展迅速的多学科交叉研究领域.相比于传统方法, 微流控技术能够实现对微量多相流体的精准操控, 可应用于化学分析、先进材料合成、蛋白质结晶、单细胞培育及检测、信息处理等领域. 该文回顾微流控器件中的多相流动现象, 概述其所涉及的流体力学机理,阐述实现多相微流控的各种方法, 并分析多相微流控技术的应用现状及面临的挑战, 最后总结针对多相微流动问题的数值模拟方法和实验测量技术, 展望多相微流控器件的研究方向及应用前景.      

工业和环境流体力学(Ⅰ)

<正> 1 引言 90年代的开始,正是对工业和环境流体力学进行综述的适当时候,因为在这10年里,将有许多流体流动问题有待解决,这些问题就是全世界都在关注的经济发展问题,人民生活质量问题,以及全球环境问题。此外,很可能,流体力学研究及其应用的方向,同其他科学和技术一样,由军事装备的设计及其在战争中的使用而引起的问题,将趋于减少;军事技术方面取得的进展,可能在许多场合应用于工业和环境流体力学(IEFM)提出的重要问题。      

以压力为基本求解变量数值模拟粘性超、跨音速流动

应用以压力为基本求解变量的SIMPLE方法 ,对一双喉喷管中的层流超音速流动和一扩压器中的紊流跨音速流动进行了数值计算。计算结果显示 ,本文的计算结果与文献数据及实验结果相符很好。表明本文方法对可压缩流动有很高的模拟精度。进而表明经过可压缩推广的SIMPLE方法适用于任何马赫数的流动计算     

流体力学在制浆造纸工程中的应用

造纸工业是流体力学的应用领域之一.本文从纸浆流动机理、湍流理论在纸页成形中的作用,中浓纸浆的流体化及涂料流变学等几方面讨论了流体力学在轻工业中的应用.     

数值模拟方法在体液流动研究中的应用与展望

计算流体力学的数值模拟技术产生于20世纪60年代,现已成功地应用到众多科学研究与工程设计领域. 从20世纪80年代开始,虽已有不少研究工作开始利用CFD方法与计算机技术对人体的血流、气管中的气流、胆汁流等流动进行数值模拟与分析,但并没有与器官功能分析和病理分析及临床应用紧密联系. 近十几年来,这方面的工作已经取得了长足的进步和发展,模拟出了譬如脑血管、颈动脉、心血管等复杂血管流动,甚至整个肺泡的活动,得到了非常有病理意义和临床价值的图像.本文介绍和评述计算人体流体动力学的历史,发展和已经取得的成果.      

二维轴对称耦合流动问题的解析解及应用

耦合流动问题与矿井开采中许多重要工程问题有密切联系:基于 Biot 三维固结理论导出了平面轴对称耦合流动与非耦合流动的场方程,得到了给定势问题的解析解.对耦合和非耦合两种情况进行了比较,并介绍了其在采矿工程中的应用.     

Non-isothermal flow diagnostics using microencapsulated cholesteric particles

The temperature and the flow field of thermo-convective liquid flows are visualized using cholesteric liquid crystal material as tracer particles. This type of tracers offers the scientifically valuable feature of measuring the flow and the temperature field simultaneously. Three thermoconvective flow configurations have been investigated successfully using liquid crystals. The results are discussed in some detail. It turns out that the liquid crystal technique is a valuable tool for thermo-convective liquid flow analysis.     

A control volume finite difference method for buoyant flow in three-dimensional curvilinear non-orthogonal co-ordinates

This paper presents a control-volume-based finite difference method in non-orthogonal curvilinear coordinates on a local basis in which the vectors and tensors are all based on the general curvilinear coordinates for buoyant flow calculations in arbitrary three-dimensional geometries. The governing equations are transformed from Cartesian co-ordinates into generalized curvilinear co-ordinates. After integrating the set of equations for the control volumes, the finite difference equations are then formulated by a proper treatment of the heat flux and stress tensors and by incorporating the QUICK scheme for the convective terms. The solution procedure then follows the one for three-dimensional Cartesian co-ordinates. Examples are given in problems of natural convection in such three-dimensional enclosures as parallelepiped enclosures and horizontal closed cylinders with differentially heated ends. In the latter case, important applications have been found in crystal growth by means of chemical vapour deposition in a cylindrical ampoule, in which uniform heat fluxes along the two ends are required in order to produce high-quality crystals. Special attention is given to the insertion of baffles in the cylinder to improve the recirculating flow patterns near the two ends.     

Viscous effects in liquid encapsulated liquid bridges

An analytical derivation of the surface deflections and the streamfunctions for the flow inside a liquid encapsulated liquid bridge has been derived using an asymptotic expansion about a small capillary number. The model assumes an initially flat and cylindrical interface under the assumption that the densities of both fluids are equal. To simplify the analysis, the top and bottom walls are assumed to be stress-free and the Reynolds number is assumed to be negligible. Flow is generated either by a moving outer wall (shear-driven flow) or by applying a temperature difference across the top and bottom walls (Marangoni-driven flow). The resulting equations show that for the shear-driven flow, as the viscosity ratio increases, the surface deflections increase monotonically. For the Marangoni-driven flow there exist values of the viscosity ratio where the surface deflections reach a minimum and then switch signs. This investigation shows that it may be possible in more realistic systems to use an outer encapsulating liquid of the proper viscosity ratio to stabilize the liquid–liquid interface during float zone crystal growth.     

The effect of far field flow on a spherical crystal growth in the undercooled melt

The effect of convective flow on a spherical crystal growth in the undercooled melt with a moderate far field flow is studied. The asymptotic solution of the evolution of the interface of the spherical crystal growth is obtained by the matched asymptotic expansion method. The analytic result shows that the convective flow in the undercooled melt has a strong effect on the evolution of spherical crystal growth. The convective flow induced by the far field flow makes the interface of the growing spherical crystal enhance its growth velocity in the upstream direction of the far field flow and inhibit growth in the downstream direction, and the interface of the decaying spherical crystal further decay in the upstream direction and inhibit decay in the downstream direction. The maximum growth velocity of the interface of the spherical crystal influenced by the far field flow is obtained.     

外加磁场对熔融半导体CZ法拉晶过程中流动场影响的数值计算

数值分析结果表明,外加磁场可以改变熔融半导体中的流型,几千高斯的磁场可以显著地减小熔体的流动,但对温度场影响不大。     

外加磁场对熔融半导体CZ法拉晶过程中流动场影响的数值计算

数值分析结果表明,外加磁场可以改变熔融半导体中的流型,几千高斯的磁场可以显著地减小熔体的流动,但对温度场影响不大。     

Effect of phase interactions on crystal stress evolution over crystal orientation space under elastoplastic deformation of two-phase polycrystalline solids

It has been known for decades that crystal stress directions move toward the vertices of the single crystal yield surface (SCYS) during plastic flow of polycrystalline solids to satisfy the deformation compatibility among crystals. The alignment of crystal stress with a SCYS vertex is affected not only by plastic anisotropy, but also by other factors such as elastic anisotropy, loading direction, and grain interactions. Among the factors contributing to the degree of alignment, the effect of phase interactions on the crystal stress evolution during plastic flow has not been extensively investigated. In this research, the effect of phase interactions on the crystal stress direction evolution is investigated using simulations of an elastoplastically deforming two-phase (Cu/Fe) polycrystalline solid calibrated to a neutron diffraction experiment. By mapping the simulated crystal stresses over the crystal orientation space, crystal-orientation-dependent nonuniform partitioning of the crystal stress between phases can be observed. An analysis of the distribution of angles between the SCYS vertex and the crystal stress based on the simulation of the two-phase material shows that the crystal stress evolution pattern during plastic flow is strongly affected by phase interactions. These interactions result in low alignment and greater dispersion angles between the crystal stresses and SCYS vertices, particularly in the strong phase.     

OPTICAL DIAGNOSTIC AND MODELING SOLUTION GROWTH PROCESS OF SODIUM CHLORATE CRYSTALS

Both a real time optical interferometric experiment and a numerical simulation of two-dimension non-steady state model were employed to study the growth process of aqueous sodium chlorate crystals. The parameters such as solution concentration distribution, crystal dimensions, growth rate and velocity field were obtained by both experiment and numerical simulation. The influence of earth gravity during crystal growth process was analyzed. A reasonable theory model corresponding to the present experiment is advanced. The thickness of concentration boundary layer was investigated especially. The results from the experiment and numerical simulation match well.     

Heating enhancement caused by a transverse control jet in hypersonic flow

Experiments are reported in which the heat flux distribution near a single circular, sonic transverse jet on a flat plate exposed to a hypersonic (Mach 6.7) freestream flow was quantitatively measured using thermochromic liquid crystals. The freestream conditions were such that the boundary layer growth on the plate ahead of the jet was laminar. The results indicate that the interaction of the jet with the freestream flow created a complex flowfield with regions of separation and reattachment which caused localised enhancements to the heat flux upstream and to the side of the jet, the magnitudes of which were sensitive to both jet plenum pressure and jet gas composition. Received 28 August 1996 / Accepted 6 June 1997     

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通过使用基于非正交网格有限体积法的FLUTRAPP (fluid flow and transport phenomena program)程序模拟了工业8\,in单晶硅提拉法生长过 程. 数值模拟结果表明,流场及提拉速 率在单晶硅生长过程中具有振荡特性,提拉速率的振荡周期大约为2\,min. 尖形磁 场的引入能够抑制坩埚中熔体流动的振荡,减小提拉速率的振幅,从而有利于提高 所生长单晶的质量.