共查询到13条相似文献，搜索用时 46 毫秒
1.
高雷诺数流动理论、算法和应用的若干研究进展 总被引：3，自引：0，他引：3
在黏性流体力学的历史发展中,Navier-Stokes (NS)方程组的 简化理论、相应算法和应用构成了不同历史时期的学科前沿、核心内 容的应用热点。以此为线索,简要评述经典边界层、多层(三层)边界 层、干扰边界层、扩散抛物化(DP) NS方程诸理论、相应算法和应用的 若干研究进展;诸理论之间以及他们与实验的关系;简化湍流计算的 一点注释以及物理分析和数值模拟相结合的一些问题。 相似文献
2.
干扰剪切流动(ISF)和边界层流动及ISF理论在计算流体力学(CFD)中的应用 总被引：1，自引：0，他引：1
简述作者提出的干扰剪切流动(ISF)理论、近壁复杂ISF理论、推论和它们在CFD中的应用.ISF是小黏性流体运动中普遍存在的一种基本流动,如驻点流、近壁黏性-无黏干扰流动,干扰可忽略时ISF的黏性部分为熟知的边界层流动.ISF理论揭示了高$Re$数流动计算的最佳坐标系和最佳网格生成.由近壁复杂ISF理论与流体运动方程组及流速在壁面无滑移条件相结合导出一组壁面相容(SC)判据,该判据提供了利用CFD仿真结果判断CFD仿真可信度的理论途径、并为近壁网格、算法和边界处理的改进和三者的更好协调、为湍流模型的评估、改进和发展提供了一种理论途径. 相似文献
3.
特征分析表明 :对原始扰动量的抛物化稳定性方程组 (PSE) ,它在亚、超音速区分别具有椭圆和抛物特性 ,给出PSE特征对马赫数的依赖关系 ,阐明PSE仅把信息对流 扩散传播特性抛物化 ,而保留了信息对流 扰动传播特性 ,因此PSE应称为扩散抛物化稳定性方程 (DPSE) 相似文献
4.
An Erratum has been published for this article in International Journal for Numerical Methods in Fluids 2005, 49(8): 933. We present a local‐analytic‐based discretization procedure for the numerical solution of viscous fluid flows governed by the incompressible Navier–Stokes equations. The general procedure consists of building local interpolants obtained from local analytic solutions of the linear multi‐dimensional advection–diffusion equation, prototypical of the linearized momentum equations. In view of the local analytic behaviour, the resulting computational stencil and coefficient values are functions of the local flow conditions. The velocity–pressure coupling is achieved by a discrete projection method. Numerical examples in the form of well‐established verification and validation benchmarks are presented to demonstrate the capabilities of the formulation. The discretization procedure is implemented alongside the ability to treat embedded and non‐matching grids with relative motion. Of interest are flows at high Reynolds number, ??(105)–??(107), for which the formulation is found to be robust. Applications include flow past a circular cylinder undergoing vortex‐induced vibrations (VIV) at high Reynolds number. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
5.
This paper extends the results of Matthies, Skrzypacz, and Tubiska for the Oseen problem to the Navier-Stokes problem. For the stationary incompressible Navier- Stokes equations, a local projection stabilized finite element scheme is proposed. The scheme overcomes convection domination and improves the restrictive inf-sup condition. It not only is a two-level approach but also is adaptive for pairs of spaces defined on the same mesh. Using the approximation and projection spaces defined on the same mesh, the scheme leads to much more compact stencils than other two-level approaches. On the same mesh, besides the class of local projection stabilization by enriching the approximation spaces, two new classes of local projection stabilization of the approximation spaces are derived, which do not need to be enriched by bubble functions. Based on a special interpolation, the stability and optimal prior error estimates are shown. Numerical results agree with some benchmark solutions and theoretical analysis very well. 相似文献
6.
Gao Zhi 《Acta Mechanica Sinica》1988,4(2):112-123
A hierarchial structure for the basic equations of fluid mechanics (BEFM) is found through the analysis of scales of length
and time that proves a measure of the rate of change of the quantities describing the motion of the fluid as well as an estimation
of the order of magnitude of various terms included in BEFM. The hierarchial structure theory shows that if (1) the characteristic
Reynolds numbersRe is larger than unity and (2) the length scale in one coordinate direction is larger than that in other coordinate directions.
BEFM can be classified into some levels according to the estimation of the order of magnitude of various terms included in
BEFM. The hierarchial structure of BEFM has two branches: one is from BLE- to BEFM inner hierarchy, the other is from EE-
to BEFM outer hierarchy, where BLE and EE are abbreviations of the boundary-layer equations and of Euler equations, respectively.
The relationship between the two branches of the hierarchial structure, the characteristics, subcharacteristics and mathematical
properties of the hierarchial equations are studied. A comparison between the present hierarchial equations and the Simplified
Navier-Stokes equations (SNSE) appeared in literatures is also made. BLE-, EE-and Inner-outer-matched (IOM) equations hierarchies
are the most important and useful three levels for solving viscous flow-fields approximately. 相似文献
7.
悬浮体力学——流体力学与胶体科学交叉的新兴学科 总被引：1，自引：0，他引：1
本文介绍了交叉新兴学科悬浮体力学的概貌.该学科发生发展在低Re数流体力学与胶体科学的交叉边缘处.它具有很广泛的应用价值,也有许多吸引人的重要理论课题.近年来在这领域中的研究工作规模十分巨大.对这学科有兴趣的人们而言,这是十分令人鼓舞的时期.在给出了本学科的基本特征和主要研究内容之后,对于相互作用着的低Re数、低Stk数、高Kn数悬浮粒子的运动学,对于在均匀悬浮体中的相对布朗扩散,对于非均匀单分散与多分散悬浮体中的绝对布朗扩散,对于稀释单分散和多分散悬浮体中的重力沉降,对于悬浮粒子的布朗碰并、重力碰并和纯变形场碰并,以及对于高Pcclet数与低Pcclet数下的悬浮体的有效粘性等问题,本文都作了简要的论述. 相似文献
8.
A new full discrete stabilized viscosity method for the transient Navier-Stokes equations with the high Reynolds number （small viscosity coefficient） is proposed based on the pressure projection and the extrapolated trapezoidal rule. The transient Navier-Stokes equations are fully discretized by the continuous equal-order finite elements in space and the reduced Crank-Nicolson scheme in time. The new stabilized method is stable and has many attractive properties. First, the system is stable for the equal-order combination of discrete continuous velocity and pressure spaces because of adding a pres- sure projection term. Second, the artifical viscosity parameter is added to the viscosity coefficient as a stability factor, so the system is antidiffusive. Finally, the method requires only the solution to a linear system at every time step. Stability and convergence of the method is proved. The error estimation results show that the method has a second-order accuracy, and the constant in the estimation is independent of the viscosity coefficient. The numerical results are given, which demonstrate the advantages of the method presented. 相似文献
9.
Taylor-Hood finite elements provide a robust numerical discretization of Navier-Stokes equations (NSEs) with arbitrary high order of accuracy in space. To match the accuracy of the lowest degree Taylor-Hood element, we propose a very efficient time-stepping methods for unsteady flows, which are based on high-order semi-implicit backward difference formulas (SBDF) and the inclusion of grad -div term in the NSE. To mitigate the impact on the numerical accuracy (in time) of the extrapolation of the nonlinear term in SBDF, several variants of nonlinear extrapolation formulas are investigated. The first approach is based on an extrapolation of the nonlinear advection term itself. The second formula uses the extrapolation of the velocity prior to the evaluation of the nonlinear advection term as a whole. The third variant is constructed such that it produces similar error on both velocity and pressure to that with fully implicit backward difference formulas methods at a given order of accuracy. This can be achieved by fixing one-order higher than usually done in the extrapolation formula for the nonlinear advection term, while keeping the same extrapolation formula for the time derivative. The resulting truncation errors (in time) between these formulas are identified using Taylor expansions. These truncation error formulas are shown to properly represent the error seen in numerical tests using a 2D manufactured solution. Lastly, we show the robustness of the proposed semi-implicit methods by solving test cases with high Reynolds numbers using one of the nonlinear extrapolation formulas, namely, the 2D flow past circular cylinder at Re=300 and Re = 1000 and the 2D lid-driven cavity at Re = 50 000 and Re = 100 000. Our numerical solutions are found to be in a good agreement with those obtained in the literature, both qualitatively and quantitatively. 相似文献
10.
The conditions of onset and the character of the oscillations developing behind a circular cylinder located above a plane wall (screen) in a flow with a velocity profile of the boundary layer type are studied numerically. The dependence of the critical Reynolds number (at which a steady flow regime in the wake behind the cylinder is replaced by an oscillatory regime) on the cylinder-wall gap and the free-stream boundary layer thickness is found. 相似文献
11.
On the basis of Stokes separated flows, examples of separated flows described by the Navier-Stokes equations of a viscous incompressible fluid are constructed. These flows are represented by series convergent in a certain non-zero neighborhood of a flat contour immersed in the flow. In this neighborhood, the series have the same structure as those for the basic Stokes flows. Examples of the regions in which the series segments chosen give only a slight deviation from the numerical solutions of the Navier-Stokes equations are presented. The comparison between inviscid separated flows (without the no-slip condition on the contour) and viscous flows of the same structure (with the no-slip condition) shows that the viscosity does not play a decisive role in the formation of separation or the type of streamline approach to or departure from the contour. 相似文献
12.
Kyung H. Ahn 《International Journal of Heat and Fluid Flow》1992,13(4):340-346
A two-dimensional oscillating flow analysis was conducted simulating the gas flow inside Stirling engine heat exchangers. Both laminar and turbulent oscillating pipe flow were investigated numerically for Remax = 1,920 (Va = 80), 10,800 (Va = 272), 19,300 (Va = 272), and 60,800 (Va = 126). The results are here compared with experimental results of previous investigators. Predictions of the flow regime on present oscillating flow conditions are also checked by comparing velocity amplitudes and phase difference with those from laminar theory and quasi-steady profile. A high Reynolds number k-ε turbulence model was used for turbulent oscillating pipe flow. Finally, the performance of the k-ε model was evaluated to explore the applicability of quasi-steady turbulent models to unsteady oscillating flow analysis. 相似文献
13.
This paper investigates the unsteady stagnation-point flow and heat transfer over a moving plate with mass transfer, which is also an exact solution to the unsteady Navier-Stokes(NS) equations. The boundary layer energy equation is solved with the closed form solutions for prescribed wall temperature and prescribed wall heat flux conditions. The wall temperature and heat flux have power dependence on both time and spatial distance. The solution domain, the velocity distribution, the flow field, ... 相似文献