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1.
本文以弯道理想不可压缩流动的流线和等势线为曲线坐标系给出了弯道内不可压缩粘性振荡流动的一阶解以及边界层流型下的二阶解,以直角弯道为例对弯道內的粘性振荡流动以及二次流的影响进行了讨论。  相似文献   

2.
沈建伟  瞿章华 《力学学报》1992,24(1):102-108
本文采用张量形式的粘性激波层方程,用空间推进的数值方法计算了球锥、椭球锥有攻角高超音速绕流问题,并计算了组合椭球锥的粘性绕流,从而说明了本文的方法可推广应用于一般外型飞行器的小攻角绕流计算问题。文中考虑了在高超音速流动条件下空气的非平衡化学反应,认为化学反应的速率是有限的  相似文献   

3.
气液两相瞬变流的流固耦合模型研究   总被引:2,自引:0,他引:2  
传统的气液两相流瞬态分析和管道动力响应计算是分开的,存在一定的缺陷.针对石油工业中常见的多相混输问题,介绍了常见的气液两相流瞬态模型和流固之间存在的耦合机理,在不作薄壁管假设的前提下推导出了气液两相瞬变流的流固耦合模型.与现有相似模型的对比分析表明,这一模型比较全面地考虑了流体和管道的特性以及不同的耦合形式,可以适应实验和/或仿真研究的需要.  相似文献   

4.
К.  ВВ 程屏芬 《力学进展》1991,21(2):245-261
本文介绍了剪切层(边界层,Poiseujlle.流、分离流、尾流)中层流向湍流转捩过程的连续各阶段的实验研究结果,包括:给定流动对外部扰动的敏感性,产生的波(拟序结构)的线性发展,以及引起有序的层流流态破坏的非线性过程.  相似文献   

5.
高智 《力学学报》1990,22(1):9-19
对不可压缩层流二维干扰流动,本文提出一个干扰流动(IF)理论。IF理论要点为:1)干扰流动沿主流的法向被分为三层即粘性层、干扰层和无粘层,引进了法向动量交换为主导过程的干扰层概念。2)利用力学守恒律、三层匹配关系及文中引进的干扰模型,把三层的空间尺度及惯性-粘性诸力的数置级表示为单参数m的函数,m<1/2·3)导出描述各层流动的控制方程、导出描述全城流动的控制方程为简化Navie-Stokes(SNS)方程。IF理论适用于不存在分离的附着干扰流动以及存在分离的大范围干扰流动,经典边界层(CBL)理论和流动分离局部区域Triple-Deck(TD)理论分别是本文理论在参数m=O和1/4时的两个特例,本文理论容易推广到可压缩、三维及湍流流动。  相似文献   

6.
IntroductionTheconceptofthesecondgradefluidcanbedevelopedasanexpansionintermsoffadingmemorytotheNewtonianfluid .Insodoing ,higherorderderivativesofthevelocityfieldarerequired.However,secondorderfluidmayprovideonlyanapproximationtorealviscoelasticbehavior.Thephysicalmeaning ,ifany ,ofthehighorderderivativesisunclearnevertheless,theRivlinEricksensecondorderfluidiscommonlyusedandfurtherstudyseemswarranted .TheStokesflowsolutionsandthecreepingsecondgradefluidflowsolutionsarepresentedqualitativel…  相似文献   

7.
Coriolis质量流量计及其原理分析   总被引:2,自引:0,他引:2  
分析了质量流量计的工作原理,并讨论了有关频率和仪表系数的计算.  相似文献   

8.
周伟江  汪翼云 《力学学报》1994,26(5):513-520
为使返回舱安全、稳定、可靠地飞行,准确地计算其周围的复杂绕流流场,对飞船的初步设计是十分必要的。用Harten-Yee的二阶迎风TVD有限差分格式求解薄层N-S方程,模拟了返回舱三维高超声速流场,M_∞=7.35,Re_∞=7.5×10 ̄5,α=10°、20°。给出了详细的绕流结构,不同攻角、不同子午面上的物面压力分布与Moseley和wells的实验数据进行了比较,符合较好。通过分析表明,在一定的攻角下,倒锥体上低压区压力的计算精度,对力矩系数及压心位置仍有明显的影响。  相似文献   

9.
壁滑移现象对粘弹性流体狭缝流及环隙流的影响   总被引:1,自引:0,他引:1  
本文利用作者已发展的方法,研究了粘弹性流体在狭缝流及环隙流中壁滑移的影响,文中选用了四参数 oldroyd 模型作为此类流体的本构方程,研究发现当壁滑移现象出现时,其速度分布、体积流量以及压力降均表现异常,因此,可以推断质量和热量传递也将受到影响。  相似文献   

10.
侧柱与串列双柱绕流之间的干扰   总被引:1,自引:0,他引:1  
本文给出了关于串列双柱与创柱间流动干扰的实验研究结果。当三个圆柱排成等边三角形并靠得很近时,由于三圆柱间强烈的缝隙流动,大大地改变了绕流其中的串列双圆柱的流态。特别,当三圆柱中心距等于二倍圆柱直径时,在串列双柱的前、后柱之间形成了强烈的偏斜的缝隙流,出现了独特的压力分布以及要比单柱高出三倍以上的旋涡脱落频率。  相似文献   

11.
In the present study, a high-order compact finite-difference lattice Boltzmann method is applied for accurately computing 3-D incompressible flows in the generalized curvilinear coordinates to handle practical and realistic geometries with curved boundaries and nonuniform grids. The incompressible form of the 3-D nineteen discrete velocity lattice Boltzmann method is transformed into the generalized curvilinear coordinates. Herein, a fourth-order compact finite-difference scheme and a fourth-order Runge-Kutta scheme are used for the discretization of the spatial derivatives and the temporal term, respectively, in the resulting 3-D nineteen discrete velocity lattice Boltzmann equation to provide an accurate 3-D incompressible flow solver. A high-order spectral-type low-pass compact filtering technique is applied to have a stable solution. All boundary conditions are implemented based on the solution of the governing equations in the 3-D generalized curvilinear coordinates. Numerical solutions of different 3-D benchmark and practical incompressible flow problems are performed to demonstrate the accuracy and performance of the solution methodology presented. Herein, the 2-D cylindrical Couette flow, the decay of a 3-D double shear wave, the cubic lid-driven cavity flow with nonuniform grids, the flow through a square duct with 90° bend and the flow past a sphere at different flow conditions are considered for validating the present computations. Numerical results obtained show the accuracy and robustness of the present solution methodology based on the implementation of the high-order compact finite-difference lattice Boltzman method in the generalized curvilinear coordinates for solving 3-D incompressible flows over practical and realistic geometries.  相似文献   

12.
In this paper, we present the application of a finite element scheme to full three-dimensional incompressible flow around a cube mounted on the wall in a channel. This scheme is based on the Petrov-Galerkin weak formulation using exponential weighting functions. The incompressible Navier-Stokes equations are numerically integrated in time by using a fractional step strategy with a second-order accurate Adams-Bashforth scheme. The workability and validity of the present approach are demonstrated through the results of streamlines and pressure coefficients in the flow field up to high Reynolds number regimes.  相似文献   

13.
Both compressible and incompressible Navier-Stokes solvers can be used and are used to solve incompressible turbulent flow problems. In the compressible case, the Mach number is then considered as a solver parameter that is set to a small value, M ≈0.1, in order to mimic incompressible flows. This strategy is widely used for high-order discontinuous Galerkin (DG) discretizations of the compressible Navier-Stokes equations. The present work raises the question regarding the computational efficiency of compressible DG solvers as compared to an incompressible formulation. Our contributions to the state of the art are twofold: Firstly, we present a high-performance DG solver for the compressible Navier-Stokes equations based on a highly efficient matrix-free implementation that targets modern cache-based multicore architectures with Flop/Byte ratios significantly larger than 1. The performance results presented in this work focus on the node-level performance, and our results suggest that there is great potential for further performance improvements for current state-of-the-art DG implementations of the compressible Navier-Stokes equations. Secondly, this compressible Navier-Stokes solver is put into perspective by comparing it to an incompressible DG solver that uses the same matrix-free implementation. We discuss algorithmic differences between both solution strategies and present an in-depth numerical investigation of the performance. The considered benchmark test cases are the three-dimensional Taylor-Green vortex problem as a representative of transitional flows and the turbulent channel flow problem as a representative of wall-bounded turbulent flows. The results indicate a clear performance advantage of the incompressible formulation over the compressible one.  相似文献   

14.
A Petrov-Galerkin finite element method using exponential weighting functions for the computation of three-dimensional incompressible viscous flow problems is presented. The unsteady incompressible Navier-Stokes equations are discretized by means of a semi-explicit scheme with respect to the time variable. As the time-marching scheme, the fractional step method is used effectively. Numerical results demonstrate that the present method is capable of solving the cubic cavity flow accurately and in a stable manner for Reynold numers up to 104  相似文献   

15.
In this paper, we propose a novel incompressible finite-difference lattice Boltzmann Equation (FDLBE). Because source terms that reflect the interaction between phases can be accurately described, the new model is suitable for simulating two-way coupling incompressible multiphase flow. The 2-D particle-laden flow over a backward-facing step is chosen as a test case to validate the present method. Favorable results are obtained and the present scheme is shown to have good prospects in practical applications. The project supported by the National Natural Science Foundation of China (60073044), and the State Key Development Programme for Basic Research of China (G1999022207). The English text was polished by Guowei Yang and Yunming Chen.  相似文献   

16.
In this paper, a local radial basis function–based semi-Lagrangian lattice Boltzmann method (RBF-SL-LBM) is proposed. This is a mesh-free method that can be used for the simulation of incompressible flows. In this method, the collision step is performed locally, which is the same as in the standard LBM. In the meanwhile, the steaming step is solved in a semi-Lagrangian framework. The distribution functions at the departure points, which may be not the grid points in general, are computed by the local radial basis function interpolation. Several numerical tests are conducted to validate the present method, including the lid-driven cavity flow, the steady and unsteady flow past a circular cylinder, and the flow past an NACA0012 airfoil. The present results are in good agreement with those published in the previous literature, which demonstrates the capability of RBF-SL-LBM for the simulation of incompressible flows.  相似文献   

17.
全速解法在湍流跨音速流动中的应用   总被引:1,自引:0,他引:1  
本文对不可压流动的常用算法SIMPLE算法进行了推广,使其能计算从亚音速到超音速一定马赫数范围内的流动,这里,可压缩流动和不可压缩流动的数值自满实现了统一,称为全速解法本文对全速解法在二维流动计算中的应用性进行了初步的研究,采用了非交错网格的有限体积方法对控制方程进行离散,并用动量插值法来求得连续方程中单元边界上的变量值,本文对全速解法在二维层流的计算效果进行了考核,而后又将此算法在湍流跨音速流动中应用,计算表明本方法是成功的,能够很好地反映各种马赫数下的流场特性。  相似文献   

18.
The connection between the compressible flow of liquid crystals with low Mach number and the incompressible flow of liquid crystals is studied in a bounded domain. In particular, the convergence of weak solutions of the compressible flow of liquid crystals to the weak solutions of the incompressible flow of liquid crystals is proved when the Mach number approaches zero; that is, the incompressible limit is justified for weak solutions in a bounded domain.  相似文献   

19.
Journal of Applied Mechanics and Technical Physics - In the present study, entropy generation in a non-axisymmetric steady-state incompressible viscous flow over a single rotating porous disk is...  相似文献   

20.
We present a parameter‐free stable maximum‐entropy method for incompressible Stokes flow. Derived from a least‐biased optimization inspired by information theory, the meshfree maximum‐entropy method appears as an interesting alternative to classical approximation schemes like the finite element method. Especially compared with other meshfree methods, e.g. the moving least‐squares method, it allows for a straightforward imposition of boundary conditions. However, no Eulerian approach has yet been presented for real incompressible flow, encountering the convective and pressure instabilities. In this paper, we exclusively address the pressure instabilities caused by the mixed velocity‐pressure formulation of incompressible Stokes flow. In a preparatory discussion, existing stable and stabilized methods are investigated and evaluated. This is used to develop different approaches towards a stable maximum‐entropy formulation. We show results for two analytical tests, including a presentation of the convergence behavior. As a typical benchmark problem, results are also shown for the leaky lid‐driven cavity. The already presented information‐flux method for convection‐dominated problems in mind, we see this as the last step towards a maximum‐entropy method capable of simulating full incompressible flow problems. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

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