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1.
本文提出一种求解离心式叶轮流场的数值方法,将流动求解区域离散为有限个由流线构成其边界的单元,采用伽辽金法建立的单元方程在一条流束上集合为方程组,流线上的节点坐标亦作为未知量包含在有限元方程中,通过扫描计算,逐步解得流线位置及流动参数。本文应用叶轮的通流理论流动模型,采用扫描流速有限元方法对离心泵叶轮流场进行了计算,并与有关文献作了比较。  相似文献   

2.
引言对于任意形状流道中的定常粘性层流问题,作者曾在文献中提出了一种流线迭代法来进行数值计算。由于流线迭代法是在任意非正交网格中进行有很差分计算,它可以根据流动区域的特点来画出不等距的非正交网格,从而可以在保证精度的前提下减少计算工作量。正因为流线迭代具有方法简便,计算速度快等优点,这种方法可以广泛地应用于工程计算之中,作者曾用流线迭代法计算了叶轮机械中的粘性流动。(如文献)  相似文献   

3.
本文针对[8]所提出的问题,论述了流线曲率法两种计算问题(设计计算和分析计算)的速度梯度方程的奇异点和流量方程的最大流量点。并在此基础上论证了流线曲率通流和管流计算M数的限制是M_m<1,而不是M_w<1,从而可以得到跨声速流场。  相似文献   

4.
韩向科  苏波  郭彤  宋凯 《力学季刊》2023,44(1):113-121
在传统流线迎风Petrov-Galerkin (SUPG)有限元法基础上,通过对稳定因子关键参数进行分析,提出了基于流向投影的最优特征高度参数确定方法,同时针对不可压流动引入变量分裂算法,发展了一种可用于高雷诺数不可压流动计算的高精度稳定化SUPG方法.详细地给出了三角形单元基于流向的最优特征高度确定方法的分析过程,并给出了基于分裂算法的有限元计算步骤和公式.采用该方法对典型的方腔拖曳、圆柱绕流流动问题进行了分析,在网格较稀疏,且雷诺数较大的情况下,依然可以得到稳定的计算结果,从而验证了该方法的稳定性、有效性,对实际工程应用具有积极的意义.  相似文献   

5.
本文提出一个通过坐标变换把外部流场问题转化为内部流场问题来处理的方法。从而可将计算内部流场粘性流动的流线迭代法推广应用到外部流场中。用这种方法,本文对同时含有内流场和外流场的粘性流动问题进行数值计算。最后给出了计算实例。  相似文献   

6.
复杂边界条件下渗流场流线分布研究   总被引:17,自引:2,他引:15  
流线分布研究已受到油藏工程师们的普遍关注。本文从无限大油藏稳态渗流场基本解出发,结合边界元方法求解出复杂边界条件下稳态渗流场的势分布,以此为基础提出了流线场的生成办法,并给出了应用实例。本文方法的优点在于求解过程中将问题的维数降低了一维,减少了计算量;计算精度较高且具有一定的普遍应用性;适应于求解任意形状的包括定压、定流量或混合边界在内的组合边界问题。实例表明,利用本文方法产生的流线分布因能够较为直观地反映出油藏流体在注采井间的运动轨迹,为优化井网和注入方案提供了重要依据。  相似文献   

7.
基于非正交多松弛系数格子Boltzmann(MRT-LB)方法建立了适用于多孔方腔自然对流计算模型,选取典型热流动问题分析了非正交转换矩阵的MRT-LB模型数值准确性和运算效率,布置两种粗糙多孔方腔模型进行研究。讨论了Rayleigh数、粗糙单元个数n、粗糙单元横纵比A等参数对方腔内流动传热的影响,同时给出了各个参数条件下腔内流场与温度场分布。结果表明,非正交MRT-LB模型具有很好的数值准确性和收敛速度,布置粗糙单元使得壁面处流线等温线发生变形,增大粗糙元单元个数n或横纵比A均会恶化方腔传热。  相似文献   

8.
本方法可视为时间推进有限面积法和流线迭代法的一种结合。在本方法中,网格是由一族流线及一族固定的节距线所形成的。流线的位置预先并不知道,在计算过程中需要逐步加以修正。采用流线作为一族网格线可使网格线的分布更为合理,并使差分格式大大简化。  相似文献   

9.
关于渗流中流线不封闭的特性和条件   总被引:2,自引:0,他引:2  
陈金娥 《力学季刊》2003,24(3):346-350
本文对于流体在多孔介质中流动的特性进行理论研究和数值计算,提出两个关于渗流中流线不封闭的特性和条件,得到了在一般工程实际情况中的多孔介质区域内部不存在封闭流线的结论。本文以突变截面圆管中不可压缩渗流为算例,利用半人工瞬变方法进行数值计算,得到流体在充满多孔介质的突扩截面圆管和突缩截面圆管中流动时关于速度分布和压力分布的结果。由此表明,在突变截面附近的渗流区域中不存在回流和分离流,也不存在封闭的流线。渗流的这些流动特性不同于在无多孔介质的空间区域中的流动特性。  相似文献   

10.
考虑边界层影响时溢流坝动水压强分布规律的研究   总被引:1,自引:0,他引:1  
根据溢流坝反弧段水流运动的基本方程,考虑水流边界层的影响,在流线曲率同心圆假设条件下,得到了溢流坝反弧段水流压强计算的表达式。通过引入近壁薄流层要领和缓和过渡流线假设,在水工模型试验的基础上,得到了溢流坝反弧段水流流线曲率半径的计算公式,使反弧段离心力影响范围内的水流流线曲率光滑连续,从而得到反弧段水流压强分布规律的统一表达式,该表达式能够反映水流压强沿反弧法线方向及切线方向的变化规律。  相似文献   

11.
This paper details an approach to modelling gas–solid fluidized beds using the two‐fluid granular temperature model. Details concerning the difficulties associated with the boundary conditions, particularly for curved boundaries, are described along with a novel means of obtaining the internal stress of the solid‐phase, in part, by solving an implicit equation. This results in a scheme that is stable even when the solid volume fraction is close to maximum packing. A transient, mixed finite element discretization is used to solve the multi‐phase equations with a discontinuous finite element representation of the granular temperature and continuity equations. A new solution method is proposed to solve the coupled momentum and continuity equations based on Arnoldi iteration. Two fluidized beds are modelled, one in the bubbling regime and the other in the slugging regime. These simulations are compared with experiments. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

12.
A. B. Mazo 《Fluid Dynamics》2002,37(6):913-918
Plane ideal incompressible flow in a rectangular channel partitioned by a thin permeable barrier (lattice) is considered. In flowing through the lattice the stream suddenly (jumpwise) changes direction and loses energy. The flow is assumed to be vortical; the vorticity is discontinuous on the lattice. A mathematical formulation of the problem for the stream function is proposed in the form of a nonlinear elliptic equation with coefficients discontinuous on the lattice line. A numerical solution is constructed using the finite-element iteration method. The results of the numerical simulation show how the flow velocity profile in the channel can be controlled by means of permeable barriers.  相似文献   

13.
环形激波聚焦流场特性的数值研究   总被引:1,自引:0,他引:1  
针对环形激波聚焦过程产生的高温、高压特性,采用间断有限元方法模拟了环形激波在同轴圆柱 形激波管内的聚焦流场特性。计算结果表明,采用间断有限元方法能够有效地捕捉激波聚焦过程形成的二次 激波、涡环、三波交点和球面双马赫反射等主要流动特征。此外,通过改变环形管道内外半径对聚焦流场进行 模拟发现,环形管道外径对中心轴线上聚焦峰值压力的大小和位置影响较小,环形管道内径对中心轴线上聚 焦峰值压力的大小和位置影响较大。计算结果可以为工程应用提供一定的理论指导。  相似文献   

14.
A numerical method for the simulation of compressible two‐phase flows is presented in this paper. The sharp‐interface approach consists of several components: a discontinuous Galerkin solver for compressible fluid flow, a level‐set tracking algorithm to follow the movement of the interface and a coupling of both by a ghost‐fluid approach with use of a local Riemann solver at the interface. There are several novel techniques used: the discontinuous Galerkin scheme allows locally a subcell resolution to enhance the interface resolution and an interior finite volume Total Variation Diminishing (TVD) approximation at the interface. The level‐set equation is solved by the same discontinuous Galerkin scheme. To obtain a very good approximation of the interface curvature, the accuracy of the level‐set field is improved and smoothed by an additional PNPM‐reconstruction. The capabilities of the method for the simulation of compressible two‐phase flow are demonstrated for a droplet at equilibrium, an oscillating ellipsoidal droplet, and a shock‐droplet interaction problem at Mach 3. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

15.
In this paper the discontinuous system with one parameter perturbation is considered. Here the unperturbed system is supposed to have at least either one periodic orbit or a limit cycle. The aim is to prove the continuation of the periodic orbits under perturbation by means of the bifurcation map and the zeroes of this map imply the periodic orbits for the perturbed system. The tools for this problem are jumps of fundamental matrix solutions and the Poincare map for discontinuous systems. Therefore, we develop the Diliberto theorem and variation lemma for the system with discontinuous right hand side. At the end, as application of our method, the effect of discontinuous damping on Van der pol equation, and the effect of small force on the discontinuous linear oscillator with add a ·sgn(x) are considered.  相似文献   

16.
Transport equations in integral form are well established for analysis in continuum fluid dynamics but less so for solid mechanics. Four classical continuum mechanics transport equations exist, which describe the transport of mass, momentum, energy and entropy and thus describe the behaviour of density, velocity, temperature and disorder, respectively. However, one transport equation absent from the list is particularly pertinent to solid mechanics and that is a transport equation for movement, from which displacement is described. This paper introduces the fifth transport equation along with a transport equation for mechanical energy and explores some of the corollaries resulting from the existence of these equations. The general applicability of transport equations to discontinuous physics is discussed with particular focus on fracture mechanics. It is well established that bulk properties can be determined from transport equations by application of a control volume methodology. A control volume can be selected to be moving, stationary, mass tracking, part of, or enclosing the whole system domain. The flexibility of transport equations arises from their ability to tolerate discontinuities. It is insightful thus to explore the benefits derived from the displacement and mechanical energy transport equations, which are shown to be beneficial for capturing the physics of fracture arising from a displacement discontinuity. Extended forms of the Rankine–Hugoniot conditions for fracture are established along with extended forms of J -integrals.  相似文献   

17.
The Runge-Kutta discontinuous Galerkin method together with a refined real-ghost fluid method is incorporated into an adaptive mesh refinement environment for solving compressible multifluid flows, where the level set method is used to capture the moving material interface. To ensure that the Riemann problem is exactly along the normal direction of the material interface, a simple and efficient modification is introduced into the original real-ghost fluid method for constructing the interfacial Riemann problem, and the initial conditions of the Riemann problem are obtained directly from the solution polynomials of the discontinuous Galerkin finite element space. In addition, a positivity-preserving limiter is introduced into the Runge-Kutta discontinuous Galerkin method to suppress the failure of preserving positivity of density or pressure for the problems involving strong shock wave or shock interaction with material interface. For interfacial cells in adaptive mesh refinement, the data transfer between different grid levels is achieved by using a L2 projection approach along with the least squares fitting. Various numerical cases, including multifluid shock tubes, underwater explosions, and shock-induced collapse of a underwater air bubble, are computed to assess the capability of the present adaptive positivity-preserving RKDG-GFM approach, and the simulated results show that the present approach is quite robust and can provide relatively reasonable results across a wide variety of flow regimes, even for problems involving strong shock wave or shock wave impacting high acoustic impedance mismatch material interface.  相似文献   

18.
Three kinds of grid system based on C-type grid are examined in order to reveal their relative flow characteristics of the turbomachinery cascade, especially near the trailing edge and wake. Here, a semi-conservative interpolation technique to treat the discontinuous boundary condition along the periodic boundary is proposed and is applied on the patched-type grid structure. Computational results are presented to see the influence of trailing-edge grid structure on the Navier-Stokes solutions for the high-turning transonic turbine cascade.  相似文献   

19.
一维半无限压电杆的广义的热冲击问题   总被引:3,自引:2,他引:1  
采用具有两个热松驰时间的G-L广义热弹性理论,研究了一维无限无限长杆在其端部受到热冲击时的边值问题,借助于拉普拉斯正、反变换技术,在所考虑时间非常短的情况下,对问题进行了求解。得到了位移及温度分布的近似妥析角,发现位移及温度分布中分别存在两上阶跃点,并通过数值计算,把温度的分布规律用图形反映了出来,从温度的分布图上可以看出,当任何x的值大于第二个阶跃点的位置值时,温度值都是零,也即在当前所绘定的时刻,热以波的形式沿压电杆仅传播到第二阶跃点的位置,而在第二个阶跃点之后,压电杆上的温度分布保持初始温度;定不同时刻,热波波前的位置也将相应的在压电杆上移动,也即热波波前在压电杆上的位置随考虑时刻不同而不同,这与经典的热传导是完全不同的,它说明热是以波的形式以有限的速度,而不是以无限的速度在介质中进行传播的。  相似文献   

20.
A mixed time discontinuous space-time finite element scheme for secondorder convection diffusion problems is constructed and analyzed. Order of the equation is lowered by the mixed finite element method. The low order equation is discretized with a space-time finite element method, continuous in space but discontinuous in time. Stability, existence, uniqueness and convergence of the approximate solutions are proved. Numerical results are presented to illustrate efficiency of the proposed method.  相似文献   

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