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1.
We present a space‐time finite element method capable of dealing with flows in multiple co‐rotating reference frames. Since equal order interpolation is used for all degrees of freedom, Galerkin/least‐squares stabilization is applied. We give a detailed derivation of the equations involved, introduce the variational form, present the stabilization parameters, and also discuss implementation issues. Numerical examples in 2D and 3D show generality and efficiency of the method, if steady‐state behavior of rotating components is sufficient for the CFD analysis. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
2.
This experimental investigation deals with transition phenomena of a separated boundary layer under unsteady inlet flow conditions.
The main purpose of this investigation is to understand the influence of the rotor-stator interaction in turbomachinery on
the subsequent, highly loaded boundary layer. The research project is divided into two phases. In the first phase, which has
been completed recently, only the variation of mean velocity caused by upstream blades was simulated in the experiments while
the free-stream turbulence intensity was retained at a constant low level. The experiments are carried out in an Eifel-type
wind tunnel to investigate the laminar separated boundary layer of a flat plate under oscillating inlet conditions. The adverse
pressure gradient, similar to that of turbomachines, is generated by the contoured upper wall. The unsteadiness is produced
by a rotating flap located downstream of the test section. The reduced frequency, the amplitude and the mean Reynolds number
are varied to simulate the conditions prevailing in turbomachines. In addition to the Kelvin–Helmholtz instability of the
separated shear layer, a lower frequency instability was observed. This is frequently referred to as `free shear layer flapping'
and results in two distinctly different ways of re-attachment, depending primarily on the Reynolds number. For low momentum
thickness Reynolds numbers at the separation point, large-scale vortices locked to the frequency of the unsteady main flow
are identified. They originate nearly at the top of the separation bubble and are ejected downstream. A fully turbulent boundary
layer develops after these vortices mix out. For higher Reynolds numbers, transition is completed within a short length of
the free shear layer and there-attachment region. The characteristic momentum thickness Reynolds number separating these two
regimes in unsteady flow is about 125. The Strouhal number (reduced frequency) does not appear to have any significant effect.
Based on the experimental results, this behaviour is discussed in some detail.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
The method in [1] has been extended to the case of rotational flow in this paper. A new method for dealing with the shock
wave is presented. This method has the advantages of both the shock-fitting and the shock capturing methods. The direct problem
and the mixed direct-inverse problem of the rotational flow in a transonic plane cascade at both design and off design conditions
are solved, and the results show that the present method has rapid convergence rate and high accuracy even for the flow with
moderately strong shocks.
The calculations have been carried out on the DPS-8 computer, and for the direct problem, only 50–80 iterations are needed,
and 50–80 seconds of CPU time are required. 相似文献
4.
A 2D numerical model is proposed to simulate unsteady cavitating flows. The Reynolds‐averaged Navier–Stokes equations are solved for the mixture of liquid and vapour, which is considered as a single fluid with variable density. The vapourization and condensation processes are controlled by a barotropic state law that relates the fluid density to the pressure variations. The numerical resolution is a pressure‐correction method derived from the SIMPLE algorithm, with a finite volume discretization. The standard scheme is slightly modified to take into account the cavitation phenomenon. That numerical model is used to calculate unsteady cavitating flows in two Venturi type sections. The choice of the turbulence model is discussed, and the standard RNG k–εmodel is found to lead to non‐physical stable cavities. A modified k–εmodel is proposed to improve the simulation. The influence of numerical and physical parameters is presented, and the numerical results are compared to previous experimental observations and measurements. The proposed model seems to describe the unsteady cavitation behaviour in 2D geometries well. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
5.
叶轮机械中考虑气体粘性的激波关系黄修乾,徐建中(中国科学院工程热物理研究所北京100080)关键词激波关系,叶轮机械,粘性流动,三维流动1引言随着叶轮机械叶尖速度和负荷的提高,其内部空间激波及激波/边界层相互作用对性能的影响更加显著。就激波/边界层相... 相似文献
6.
高精度高分辨率迎风格式应用于不同速度范围内粘性流动 总被引:5,自引:2,他引:3
提出了一种适合于不同速度范围的高精度高分辨率的迎风有限差分格式,并基于此数植模型发展了适应于速度范围极宽的非定常粘性流动通用软件,不仅适用于超音速下捕捉强间断面,跨音速及高亚音速下捕捉弱间断面和滑移面,还可以精确地模拟低速情况下的粘性流动。此软件可分别用于研究内流和外流的流动特性以及预估其粘性损失。 相似文献
7.
8.
叶轮机械非定常流动研究进展 总被引:6,自引:0,他引:6
本文就叶片排进出口流场畸变型动力响应、压缩系统气动稳定性、叶轮机械非定常气动问题的数值模拟以及失速颤振轴流压气机系列转子实验等4个方面问题,从非定常气动力学角度作一概述和展望 相似文献
9.
三维透平叶片扭转颤振问题的流固耦合数值研究 总被引:4,自引:0,他引:4
颤振,尤其是失速颤振是引起叶轮机械安全事故的重要原因之一。由于叶片颤振的复杂性,过去人们一直采用半经验的方法研究叶片的颤振。本文发展了一套更精确的流固耦合计算方法,并用这种算法研究了三维透平叶片的扭转颤振。在模拟大负攻角下的颤振时发现,传播失速响应频率向固有频率靠近是振动发散的一个重要判据。通过计算得出了压比和攻角对颤振影响的特性曲线,它不但可用于判断流体激振的稳定性,而且可以研究颤振的强度。 相似文献
10.