共查询到18条相似文献,搜索用时 109 毫秒
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轴流压气机转子尖区三维紊流特性 总被引:8,自引:3,他引:5
用三维激光多普勒测速系统测量研究了低速大尺寸单级压气机设计状态转子内尖区三维紊流流场.结果表明,设计状态下叶尖泄漏涡是造成压气机转子尖部素流脉动的主要因素,其造成的高素流区沿流向逐渐扩大,并缓慢向通道中部和低叶高方向移动,紊流强度值随旋涡的增强而增大.在泄漏涡影响区域中,径向脉动水平最高,轴向和切向脉动水平相近,三个剪切应力中,轴向一径向最大,切向一径向次之,轴向一切向最小.在叶片通道后段,泄漏涡发生破裂,导致更强、更大范围的紊流脉动,剪切应力中切向-径向应力较高.在叶尖吸力面角区后半部的角涡,紊流强度大,剪切应力也大,尤其是切向-径向剪切应力. 相似文献
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旋流泵内部盐析两相流速度场的PDPA实验 总被引:2,自引:0,他引:2
以旋流式模型泵内部氯化钠盐析两相流场为研究对象,采用相位多普勒粒子测速仪(PDPA)对该泵在最优工况下的两相速度场进行了测量,给出各相在无叶腔及叶轮内部的三维速度及其对应的脉动速度分布曲线.通过对两相的周向速度、轴向速度及径向速度分布情况的分析,揭示了该型泵内盐析两相流速度场的分布特征.泵内同时存在循环流与贯通流,是强制涡旋和自由涡旋的叠加,与前人提出的流动模型相符;在叶轮进口处,液流已有强力预旋;随着半径增大,两相的周向和轴向速度呈现先增大后减小趋势,而径向速度先减小后增大,对应的脉动速度变化趋势则相反;泵内两相速度及脉动速度有滑移,但差异总体上并不显著.本文的研究有助于进一步认识盐析与流动的关系. 相似文献
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Turbulent structures in a curved circular tube were measured for three values of the curve radius to the tube radius ratio, R. Distributions of turbulent energy and axial and radial velocities are obtained in a fully developed flow region by a hot wire anemometer. Turbulent energy and Reynolds stress, become maximum in the core region, where turbulence generation becomes maximum. When R is small, turbulent generation does not balance with turbulent energy dissipation, due to a convective effect induced by secondary flow. Experimental results for Reynolds stress and turbulent energy are compared with theoretical results. Due to the secondary flow effect, for small R value flow, the ratio of these two values was not uniform in the core region. 相似文献
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LIU Nansheng LU Xiyun & ZHUANG Lixian Department of Mechanics Mechanical Engineering University of Science Technology of China Hefei China 《中国科学G辑(英文版)》2005,48(2)
Turbulent flow in an axially rotating pipe, involving complicated physical mecha- nism of turbulence, is a typical problem for the study of rotating turbulent flow. The pipe rotation induces two effects on the flow. One is the stabilizing effect due to the centrifu- gal and Coriolis forces, which accounts for the relaminarization of the turbulence[1—3] and the reduction of the friction coefficient at the pipe wall. The behavior is also related to the wall streaks inclining to the azimuthal di… 相似文献
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V. M. Zhuravlev 《Technical Physics》2009,54(1):13-24
The variational principle of maximum entropy is used to describe the dynamics of weakly nonequilibrium turbulence using the
theory of Reynolds stresses for viscous incompressible liquid flow. From this principle, equations closing the theory of Reynolds
stresses and also equations describing mean flow-turbulence interaction for 3D turbulent flows are derived. The theory is
reduced to 2D flows and weak turbulence. Thermodynamic analogues and an example of Couette flow are considered. 相似文献
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Vianello N Spada E Antoni V Spolaore M Serianni G Regnoli G Cavazzana R Bergsåker H Drake JR 《Physical review letters》2005,94(13):135001
The momentum balance has been applied to the ExB flow in the edge region of a reversed field pinch (RFP) configuration. All terms, including those involving fluctuations, have been measured in stationary condition in the edge region of the Extrap-T2R RFP experiment. It is found that the component of the Reynolds stress driven by electrostatic fluctuations is the term playing the major role in driving the shear of the ExB flow to a value marginal for turbulent suppression, so that the results are in favor of a turbulence self-regulating mechanism underlying the momentum balance at the edge. Balancing the sheared flow driving and damping terms, the plasma viscosity is found anomalous and consistent with the diffusivity due to electrostatic turbulence. 相似文献
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A robust, implicit, low-dissipation method suitable for LES/DNS of compressible turbulent flows is discussed. The scheme is designed such that the discrete flux of kinetic energy and its rate of change are consistent with those predicted by the momentum and continuity equations. The resulting spatial fluxes are similar to those derived using the so-called skew-symmetric formulation of the convective terms. Enforcing consistency for the time derivative results in a novel density weighted Crank–Nicolson type scheme. The method is stable without the addition of any explicit dissipation terms at very high Reynolds numbers for flows without shocks. Shock capturing is achieved by switching on a dissipative flux term which tends to zero in smooth regions of the flow. Numerical examples include a one-dimensional shock tube problem, the Taylor–Green problem, simulations of isotropic turbulence, hypersonic flow over a double-cone geometry, and compressible turbulent channel flow. 相似文献
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可压缩边界层转捩问题与湍流问题一直是制约高超声速飞行器发展的关键基础问题,也是近年来流体力学领域研究的热点问题.采用直接数值模拟方法,获得了空间发展的Ma=2.25超声速湍流边界层流场,通过对湍流边界层的发展状态进行评估,得出有效的Reynolds数Reθ范围约为2 600~4 600.对壁面摩阻系数开展了分解,获得了各分量的占比,对充分发展的湍流边界层进行1阶和高阶统计分析,包括形状因子、壁面律、平坦因子与偏斜因子、Reynolds应力、脉动涡量等,得到了剪切Reynolds数与动量Reynolds数之间的关系式,分析了湍流边界层壁面律的分层特性,发现湍流的间歇特性主要分布在y+ < 30的区域,并且法向速度脉动的间歇性远高于另外两者,3个方向上的Reynolds应力分布和涡量分布都存在较大差异.通过两点相关性分析和Lagrange涡结构,对近壁区湍流结构进行了分析,包括流向平面和展向平面,发现流向脉动速度的相关区域流向尺度较长,呈现狭长的特性,并且流向平面的相关系数与壁面存在一定的夹角;而在边界层外层,流向速度脉动相关区域的流向尺度变短而展向尺度增加,呈现宽胖型.研究结果进一步加深了对超声速湍流边界层的认识,为下一步湍流边界层的流动控制奠定了基础. 相似文献
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We present the results of an experimental investigation into the nature and structure of turbulent pipe flow at moderate Reynolds numbers. A turbulence regeneration mechanism is identified which sustains a symmetric traveling wave within the flow. The periodicity of the mechanism allows comparison to the wavelength of numerically observed exact traveling wave solutions and close agreement is found. The advection speed of the upstream turbulence laminar interface in the experimental flow is observed to form a lower bound on the phase velocities of the exact traveling wave solutions. Overall our observations suggest that the dynamics of the turbulent flow at moderate Reynolds numbers are governed by unstable nonlinear traveling waves. 相似文献
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Jagadish Babu Vemula 《Journal of Turbulence》2017,18(7):653-687
Shock waves in high-speed flows can drastically alter the nature of Reynolds stresses in a turbulent flow. We study the canonical interaction of homogeneous isotropic turbulence passing through a normal shock, where the shock wave generates significant anisotropy of Reynolds stresses. Existing Reynolds stress models are applied to this canonical problem to predict the amplification of the stream-wise and transverse normal Reynolds stresses across the shock wave. In particular, the efficacy of the different models for the rapid pressure–strain correlation is evaluated by comparing the results with available direct numerical simulation (DNS) data. The model predictions are found to be grossly inaccurate, especially at high-Mach numbers. We propose physics-based improvement to the Reynolds stress-transport equation in the form of shock-unsteadiness effect and enstrophy amplification for turbulent dissipation rate . The resulting model is found to capture the essential physics of Reynolds stress amplification, and match DNS data for a range of Mach numbers. Numerical error encountered at shock waves are also analysed and the model equations are cast in conservative form to obtain physically consistent results with successive grid refinement. Finally, the proposed model for canonical shock-turbulence interaction is generalised to multi-dimensional flows with shock of arbitrary orientation. 相似文献