一类旋涡精确解的构造

Navier-Stokes方程的理解求解能量最充分地反映出流动的细微性质，因而人们总是想给出某些简化情况下的Navier-Stokes方程的精确解来；而求解得面临复杂的数学运算，尤其是Navier-Stokes方程的三维特性及其非线性项难以处理，故要得到精确解是较困难的。从Stokes-Helmholtz分解出发，发现若经过一定的处理，可得到一类旋涡精确解的构造方法，并通过此方法在不同的坐标系下得到了一些新的精确解，并且将很多常见的旋涡流的精确并入到这一体系中来。这种方法给出了这些精确解的更一般的求解途径，可以说明对教科书上的这方面内容的完善和补充，相信必将有助于对旋涡流动的更清楚的了解。     

混流式水轮机固定导叶和动导叶准的三元流动计算

采用 S1、S2两类相对流面理论的准三元流动计算方法,研究了混流式水轮机固定导叶和动导叶的流场。在 S1流面上建立势函数方程,S2流面上建立流函数方程,通过两个流面的叠代计算得到该流场的流动状态。这一成果可以用来分析混流式水轮机座环和导水机构区域的水流情况。     

自由跌流的水力特性

本文应用N—S方程式,导出了压力和连续方程的解析式,求解了水流参数的半数值半解析的精确解.其结果表明,精确的理论解和一般的势流理论解的流场计算结果相差很大.本文对前人的试验研究中提出的关于出口断面水流内部是否存在负压问题进行了探讨.本文给出的理论分析结果和实测结果吻合得较好.     

确定河流横向扩散系数的直线图解法

文中以二维稳态河流水质扩散基本方程的解析解为基础，通过理论推导，提出了在忽略河流纵向弥散作用，沿河流横向与纵向取水样测定河水污染物浓度确定河流横向扩散系数的直线图解方法和相应的计算公式，与此同时还可以求出河流的平均流速．最后，通过数字算例说明了方法的具体应用     

桥墩群体绕流的复变函数理论解

桥墩群体绕流的复变函数理论解给出了在平面无旋流动条件下,多个桥墩绕流的理论解,从而将经典流体力学的桥墩绕流的理论解由单个推广到了多个.采用该理论解,通过试算得出了桥墩横断面的理论曲线,可根据预定的墩间流速进行多个桥墩绕流时的横断面设计,合理地确定桥墩间距,并可给出墩间二维流场理论解.按势流处理,水流流过该理论解给出的桥墩横断面时是无分离的,虽与实际情形有所出入,但具有理论基础,因此可供桥梁工程规划、设计参考引用.     

明渠挟沙水流的两相流模式

本文从两相流基本方程出发对明渠挟水流含沙量、流速垂线分布及近底层平均流动特性进行了理论研究，建立了一个新的泥沙扩散方程，并用大量资料进行了验证。结果表明：现有含沙量公式和流速垂线分布公式只是本文理论模式在低含沙量条件下的简化形式。当含沙量增加时，固相泥沙对流动结构的影响亦趋显著而不可忽略。精确模拟水沙流动，需要发展高级的两相湍流模式。     

平板式冰蓄冷器融冰放冷过程动态特性研究

本文建立了平板式冰蓄冷器内融冰放冷过程动态模型，应用边界层理论，并考虑自然对流现象，求得了数值解，数值解与文献实验值吻合得较好，还给出了一些工程上实用的拟合公式。     

轴流式水轮机转轮的准三维有旋流动设计

本文提出了一种基于Ｓ１流面的轴流式水轮机转轮准三维有旋流动设计方法，通过联合迭代求解转轮区和导叶区平均Ｓ２ｍ流面流动心化机前无叶片区螺旋流动，有效地考察了转轮相关部件间流动的相互影响，克服了设计中给定转轮进，出口流动条件的困难，本文基于Ｓ１流面的给定Ｖ分布的正，反问题迭代型设计方法，考虑了转轮内流动的周秒不均匀性，保证了转化的出力，通过Ｓ２ｍ流面计算定始初形叶的Ｓ１回转流面反问题与平均Ｓ２ｍ流面正     

水轮机导叶漏水影响因素分析及改进建议

水轮机的导水叶在半闭状态下漏水理往往较大，造成水能资源的损失，这个问题多年来未得发善解决白山水电厂和大连理工大学利用现代理论和计算手段，对水轮机导叶漏水问题进行了较深入的研究，提出了在导叶止水部位分别采取纵向造斜和横向造斜的方法，可以使导叶漏水量大大减少。以白山水电厂为例，计算出各种水头下采用不同的造斜量对漏水量的影响；同时也对导叶采用２支座和３支座进行了对比，当采用３支座时要比采用２支座时的漏水     

偏心环空层流螺旋流动的近似解析解

本文分析计算了石油钻井工程偏心环空中内管转动的螺旋流动，将偏心环空的三维流动简化为环空薄层内的二维流动，从黎曼空间曲面张量表达的动量方程出发，求得了偏心环空层流螺旋流动速度的近似解析解。用此方程的同心环空表达式与精确解比较，精度较高。     

Diffusion of chemically reactive species in Casson fluid flow over an unsteady permeable stretching surface

In this paper we investigate the two-dimensional flow of a non-Newtonian fluid over an unsteady stretching permeable surface. The Casson fluid model is used to characterize the non-Newtonian fluid behavior. First-order constructive/destructive chemical reaction is considered. With the help of a shooting method, numerical solutions for a class of nonlinear coupled differential equations subject to appropriate boundary conditions are obtained. For the steady flow, the exact solution is obtained. The flow features and the mass transfer characteristics for different values of the governing parameters are analyzed and discussed in detail.     

轴对称拉伸流动中大表面张力下球形液滴Stokes流动的准确解

本文采用轴对称情形下内外Stokes流动的Sampson级数解求出了轴对称拉伸流动中大表面张力下球形液滴stokes流动的准确解。该准确解表达式简单且为有限形式。文中详细分析了流线谱,粘度比对内外流的影响以及内流的速度分布和压力分布。     

WAVES GENERATED BY A SUBMERGED BODY MOVING IN STRATIFIED FLUIDS AND VERTICAL STRUCTURES OF INTERNAL WAVES

This dissertation deals with the internal waves generated by a submerged moving body in stratified fluids by combining theoretical and experimental methods. Our purpose is to provide some scientific evidences for non-acoustic detection of underwater moving bodies based on the principles of dynamics of the internal waves. An approach to velocity potentials obtained by superposing Green‘s functions of sources and sinks was proposed for Kelvin waves at the free surface or interface in a two-layer fluid. The effects of interacting surface and internal wave modes induced by a dipole on the surface divergence field were investigated. A new theoretical model formulating the interaction of a two dimensional submerged moving body with the conjugate flow in a three-layer fluid was established. An exact solution satisfying the two dimensional Benjamin Ono equation was obtained and the vertically propagating properties of the weakly nonlinear long waves were studied hy means of the ray theory and WKB method. The above theoretical results are qualitatively consistent with those obtained in the experiments conducted by the author.     

Series solution of a natural convection flow for a Carreau fluid in a vertical channel with peristalsis

An analysis has been achieved to study the natural convection of a non-Newtonian fluid(namely a Carreau fluid) in a vertical channel with rhythmically contracting walls. The Navier-Stokes and the energy equations are reduced to a system of nonlinear PDE by using the long wavelength approximation. The optimal homotopy analysis method(OHAM) is introduced to obtain the exact solutions for velocity and temperature fields. The convergence of the obtained OHAM solution is discussed explicitly. Numerical calculations are carried out for the pressure rise and the features of the flow and temperature characteristics are analyzed by plotting graphs and discussed in detail.     

Application of binding theory for seepage of viscoelastic fluid in a variable diameter capillary

The polymer solution for polymer flooding is a viscoelastic fluid. There exist both shear flow and elongational flow when the polymer solution flows in a porous medium, where an additional dissipation is involved. The additional dissipation caused by elongational deformation is often ignored while studying the flow of the fluid in a porous medium. For a complex polymer solution, the generated elongational pressure drop cannot be ignored. In a capillary of fixed diameter, the polymer solution is only impacted by the shear force, and its rheological property is pseudoplastic. Therefore the variable diameter capillary and the converging-diverging flow model with different cross sections are required to describe the flow characteristics of the polymer solution in porous media more accurately. When the polymer solution flows through the port, we have the elongational flow and the polymer molecules undergo elongational deformation elastically. By using the mechanical energy balance principle and the minimum energy principle, a mathematical model of non-Newtonian fluid inlet flow was established by Binding. On the basis of the Binding theory, with the application of the theory of viscoelastic fluid flow in the circular capillary and the contraction-expansion tube, the relations between the viscoelastic fluid flow rate and the pressure drop are obtained.     

基于颗粒流模型的颗粒材料宏-细观力学研究

基于颗粒流模型对各向同性和落雨法两种不同初始状态的颗粒材料细观参数和应力进行研究,建立了细观组构、接触力、主应力比之间的表达式。通过数值离散元程序模拟了上述两种不同初始状态钢珠的室内三轴试验。结果表明:两者应力应变曲线基本一致;各向同性试样组构初始为均匀分布的球体,落雨法试样初始组构略呈椭球体,随着加载两种试样内颗粒配位数先增加后减小,水平面内和竖直面内组构减少且面内主轴发生偏转,试样破坏后的组构张量表现为花生状椭球体;法向接触力张量表现出与组构变化相似的规律,宏观上接触力的影响数值上大于组构张量,试样破坏后法向接触力张量空间分布呈现出更明显的两端和水平面内凹陷的花生状椭球体,且面内主轴有偏转。由莫尔库仑准则得出颗粒材料内摩擦角与组构、接触力细观参数表达式,并进行了验证,因此,可通过细观参数得出颗粒材料宏观内摩擦角。     

A Three-Dimensional Desingularized High Order Panel Method Based on Nurbs

A desingularized high order panel method based on Non-Uniform Rational B-Spline （NURBS） was developed to deal with three-dimensional potential flow problems. A NURBS surface was used to precisely represent the body geometry. Velocity potential on the body surface was described by the B-spline after the source density distribution on the body surface had been solved. The collocation approach was employed to satisfy the Neurnann boundary condition and Gaussian quadrature points were chosen as both the collocation points and the source points. The singularity was removed by a combined method, so the process of the numerical computation was non-singular. In order to verify the method proposed, the unbounded flow problems of sphere and ellipsoid, the wave-making problem of a submerged ellipsoid were chosen as computational examples. It is shown that the numerical results are in good agreement with analytical solutions and other numerical results in all cases, and sufficient accuracy of numerical solution can be reached with a small number of panels.     

Electro-osmotic flow of a second-grade fluid in a porous microchannel subject to an AC electric field

Studies on electro-osmotic flows of various types of fluids in microchannel are of great importance owing to their multifold applications in the transport of liquids, particularly when the ionized liquid flows with respect to a charged surface in the presence of an external electric field. In the case of viscoelastic fluids, the volumetric flow rate differs significantly from that of Newtonian fluids, even when the flow takes place under the same pressure gradient and the same electric field. With this end in view, this paper is devoted to a study concerning the flow pattern of an electro-osmotic flow in a porous microchannel, which is under the action of an alternating electric field. The influence of various rheological and electro-osmotic parameters, e.g., the Reynolds number, Debye-Huckel parameter, shape factor and fluid viscoelasticity on the kinematics of the fluid, has been investigated for a secondgrade viscoelastic fluid. The problem is first treated by using analytical methods, but the quantitative estimates are obtained numerically with the help of the software MATHEMATICA. The results presented here are applicable to the cases where the channel height is much greater than the thickness of the electrical double layer comprising the Stern and diffuse layers. The study reveals that a larger value of the Debye-Huckel parameter creates sharper profile near the wall and also that the velocity of electro-osmotic flow increases as the permeability of the porous microchannel is enhanced. The study further shows that the electro-osmotic flow dominates at lower values of Reynolds number. The results presented here will be quite useful to validate the observations of experimental investigations on the characteristics of electro-osmotic flows and also the results of complex numerical models that are necessary to deal with more realistic situations, where electro-osmotic flows come into the picture, as in blood flow in the micro-circulatory system subject to an electric field.     

部分可渗透直立圆柱的消波作用研究

本文导出了线性波浪作用于上部可渗透的直立刚性圆柱体上的水动力的解析解。在线性有势流的假定下，用特征函数展开方法求出了内部和外部流场的解。给出了不同波浪要素及结构尺寸参数下的数值结果。由结果可知，提高可渗透性可以有效消减波幅。