稀相气固悬浮体越过沿平面匀速运动激波后的流动结构*

本文给出气固悬浮体中激波感生边界层的渐近数值分析,其中计及了作用于固体粒子的Saf-fman升力.研究结果表明粒子横越边界层的迁移导致了粒子轨道的交叉,因此对目前通用的含灰气体模型应做相应的修正.本文利用匹配渐近展开方法得到了匀速运动激波后方的两相侧壁边界层方程,详细描述了在Lagrange坐标下计算颗粒相流动参数的方法,并给出了粒子浓度很低情况下的数值结果.     

气液两相流动数学模型在同心式泡沫发生器优化中的应用

为了给冲砂洗井泡沫的制备和关键工艺设备研制提供理论基础,应用气液两相流动数学模型对泡沫发生器内部流场进行模拟计算.通过改变出气管顶端的倾角和出气管至入口变径腔距离来分析泡沫发生器内部速度和压力对流场影响,得到更科学合理的泡沫发生器结构参数.     

垂直管道中密相两相流动的解析解

本文依据文献[1]的密相两相流动的数学模型,对垂直圆管中密相两相流动进行了解析求解,分别得到了连续相和分散相的速度解析表达式.在相间阻力与相间速度差成比例时,除了在离管壁面很近的薄区之外,管道流动规律与达西渗流定律完全一致.本文验证了文献[1]的密相两相流动数学模型的假定在本文情形下是合理的.     

密相液固两相湍流K-ε-T模型及其在管道两相流中的应用

为了准确预测密相液固两相湍流流动,建立了Ｋ－ε－Ｔ模型,推导了控制方程组。利用该模型对竖直上升管中的密相液固两相流动进行了数值模拟,得到了与实验值吻合较好的结果。     

带激波的一维非定常两相流动的数值模拟

本文将处理带激波的单相气体非定常流动问题的两种高分辨数值方法(随机取样法和二阶GRP有限差分法)推广应用于气固悬浮体(亦称含灰气体)两相情况,计算了含灰气体激波管中两相激波特性、波后流场结构及气固两相流动参数随时间的变化.数值结果表明:这两种方法均能给出带有尖锐间断阵面的两相激波松弛结构.二阶GRP方法在计算精度和机时耗用等方面优于随机取样法.     

一维气液两相漂移模型的AUSMV算法研究

将AUSMV(advection upstream splitting method V)格式从计算气体动力学问题扩展至一维等温瞬态气液两相管流.阐述了采用AUSMV格式构建气液两相漂移模型数值通量的方法及边界单元的处理方法.采用Runge Kutta方法与经典的保单调MUSCL(monotone upstream centred schemes for conservation laws)方法结合Van Leer限制器,构建具有二阶时间和空间精度的数值计算方法.计算经典Zuber-Findlay激波管问题和复杂漂移关系变质量流动问题并与可靠的参考结果进行了对比.分析表明:AUSMV格式应用于气液两相流动漂移模型时计算效率高、精度高、耗散效应和色散效应小,低流速条件下能够精确地描述间断.     

隐式TVD格式在气液两相爆轰数值模拟中的应用

为研究FAE(燃料-空气炸药)爆炸参数规律,运用二维轴对称气液两相方程组模型,针对其中的气相方程组采用高分辨率的隐式TVD格式,液相方程组采用MacCormack格式,较好地对FAE气液两相爆轰产生的爆轰波的发展和传播过程进行了数值模拟,计算结果与国内外的研究结果符合良好.     

凝析油-气两相流偏微分方程组问题的求解及应用

根据凝析气藏开发的实际需要，引入凝析油－气两相拟压力、拟时间函数，建立了凝析气在双重渗透率介质中的不稳定渗流新模型，该模型为一类偏微分方程组的混合问题，本文研究了这类偏微分方程组问题的求解方法。     

液固两相圆柱绕流尾迹内颗粒扩散分布的离散涡数值研究

基于离散涡方法求得的非定常水流场和颗粒的Lagrange运动方程,数值模拟了稀疏液固两相圆柱绕流尾迹内颗粒的扩散分布．获得了流动的涡谱与3种不同St数颗粒（St=0.25,1.0,40）在流场中的分布．通过引入扩散函数来定量表示颗粒在流场中的纵向扩散强度,并计算得到了不同St数颗粒的扩散函数随时间的变化．数值结果揭示出了液固两相圆柱绕流尾迹中的颗粒扩散分布与颗粒的St数和尾涡结构密切相关:1) 中小St数(St=0.25～4.0)颗粒在运动过程中不能进入涡核区,而在旋涡结构的外沿聚集,且颗粒的St数愈大,其越远离涡核区域;2） 在圆柱绕流尾迹区域内,中小St数(St=0.25～4.0)颗粒的纵向扩散强度随其St数的增大而减小．     

Two dimension-curvilinear grid for open channel flow simulation

A mathematical model for two-dimensional flow simulation in an open channel is developed. The model is obtained through the use of a stretched curvilinear grid which defines points where velocity and surface elevation are simulated. Simulation is achieved by numerically integrating the Navier-Stokes mass and momentum equations using centred finite difference approximations of derivatives. The model uses an implicit discretization scheme, the Newton-Raphson iterative technique and a customized Gauss elimination solving algorithm. The computer program developed for this model was tested for uniform, non-uniform and unsteady flow conditions. The results have been found consistent with theoretical solutions and/or field measurements. Limitation and verification of the model is also outlined.     

Computation of dilute two-phase flow in a pump

This paper is a report on a joint project between academia and industry which is concerned with computation of dilute two-phase flow through a pump in turbulent condition. The flow field for the continuous phase is computed using the Reynolds averaged Navier–Stokes equations together with mixing length turbulence modeling. The dispersed phase is treated using the Lagrangian approach by tracking it's trajectory along which the information is passed. It is found that the bubbles and small solid particles flow out of the chamber (between the rotating impeller and the casing wall) with the conveying fluid. The solid particles of relatively bigger sizes accumulate at the low pressure zones near the cashing wall or the rotating shaft.     

An asymptotic analysis of two-phase fluid mixing

We study the motion of the slightly compressible multi-phase flow model proposed by Chen, Glimm, Sharp and Zhang. The interface velocity and constitutive law are analyzed by derivation of the exact quantity. Using singular perturbation theory, a formal asymptotic expansion is derived for the solution of the compressible equations. An asymptotic analysis in the incompressible limit, for slightly compressible flows supplies important new information to resolve nonuniqueness of the pressure difference between the two fluid species of the incompressible flow equations.Supported in part by the U.S. Department of Energy DE-FG02-90ER25084, DE-FG02-989ER2536, DE-FG03-98DP00206, the National Science Foundation DMS-0102480, the Army Research Office grant DAAD19-01-0642 and Los Alamos National Laboratory.Supported in part by the Clay Mathematics Institute.     

Finite volume approximation of degenerate two‐phase flow model with unlimited air mobility

Models of two‐phase flows in porous media, used in petroleum engineering, lead to a coupled system of two equations, one elliptic and the other degenerate parabolic, with two unknowns: the saturation and the pressure. In view of applications in hydrogeology, we construct a robust finite volume scheme allowing for convergent simulations, as the ratio μ of air/liquid mobility goes to infinity. This scheme is shown to satisfy a priori estimates (the saturation is shown to remain in a fixed interval, and a discrete L2(0,T;H1(Ω)) estimate is proved for both the pressure and a function of the saturation), which are sufficient to derive the convergence of a subsequence to a weak solution of the continuous equations, as the size of the discretization tends to zero. We then show that the scheme converges to a two‐phase flow model whose limit, as the mobility of the air phase tends to infinity, is the “quasi‐Richards equation” (Eymard et al., Convergence of two phase flow to Richards model, F. Benkhaldoun, editor, Finite Volumes for Complex Applications IV, ISTE, London, 2005; Eymard et al., Discrete Cont Dynam Syst, 5 (2012) 93–113), which remains available even if the gas phase is not connected with the atmospheric pressure. Numerical examples, which show that the scheme remains robust for high values of μ, are finally given. © 2012 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2013     

Chattering in dynamic mathematical two-phase flow models

This paper presents a chattering problem which arises in a dynamic mathematical two-phase flow model. The real system under study is also introduced, the DISS test facility, a parabolic-trough solar thermal power plant. The heat transfer fluid in the DISS facility is the steam-water mixture. A dynamic model of this plant, using Modelica as the modeling language, was previously developed in order to study its behavior. Chattering arises in the pipe model reducing the computational performance and hence limiting the applicability of the model. The problem source is studied and analysed together with an approach to the problem which is based on the smooth interpolation of some thermodynamic properties.     

Large scale petroleum reservoir simulation and parallel preconditioning algorithms research

Solving large scale linear systems efficiently plays an important role in a petroleum reservoir simulator, and the key part is how to choose an effective parallel preconditioner. Properly choosing a good preconditioner has been beyond the pure algebraic field. An integrated preconditioner should include such components as physical background, characteristics of PDE mathematical model, nonlinear solving method, linear     

Review on mathematical analysis of some two-phase flow models

The two-phase flow models are commonly used in industrial applications, such as nuclear, power, chemical-process, oil-and-gas, cryogenics, bio-medical, micro-technology and so on. This is a survey paper on the study of compressible nonconservative two-fluid model, drift-flux model and viscous liquid-gas two-phase flow model. We give the research developments of these three two-phase flow models, respectively. In the last part, we give some open problems about the above models.     

任意流场中稀疏颗粒运动方程及其性质

通过研究和比较稀疏刚性颗凿相对流体运动时所受到的各种人艇力,并考虑在不同流动条件下各作用修正问题从而得到了任意流场中稀疏颗粒运动方程的一般形式,然后分析了该方程的数学性质,采用积分变换方法对该方程的基本形式进行了理论解析,最后探讨了闰物理性质对其运动规律的影响,以及几种典型流场中稀疏颗粒的运动特性,得到了一些有意义的结论