圆柱绕流的流场特性及涡脱落规律研究

采用粒子图像测速技术对630、800及950三种雷诺数条件下的圆柱绕流场进行了实验,给出了圆柱下游沿流动方向4倍圆柱直径和垂直方向3倍圆柱直径区域内的速度场、涡量场以及涡脱落现象的时空演化规律.结果表明:圆柱尾流区域位于垂直方向约1.5~2.5倍圆柱直径范围内,随着雷诺数增大,这一范围呈现缩小趋势,而主流对涡的拉伸和输运能力有所增强;涡脱落频率随雷诺数增大而增大,小雷诺数时能够较为完整地捕捉到涡生成、脱落、发展和耗散过程,由于PIV采集频率的限制,大雷诺数条件下涡脱落整个过程不易被完整捕捉到.     

Diagnostics of bubble-mode vortex breakdown in swirling flow in a large-aspect-ratio cylinder

We report for the first time on the possible formation of regions with counterflow (bubble-mode vortex breakdown or explosion) at the center of strongly swirling flow generated by a rotating endwall in a large-aspect-ratio cylindrical cavity filled with a liquid medium. Previously, the possibility of bubble-mode breakdown was studied in detail for cylindrical cavities of moderate aspect ratio (length to radius ratios up to H/R ～ 3.5), while flows in large-aspect-ratio cylinders were only associated with regimes of self-organized helical vortex multiplets. In the present study, a regime with nonstationary bubble-mode vortex breakdown has been observed in a cylindrical cavity with H/R = 4.5.     

Modeling the separation flow around a cylinder near a screen

The nonstationary separation flow of an incompressible viscous fluid around a circular cylinder at different distances from a plane screen is investigated in a numerical experiment.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 50, No. 2, pp. 188–195, February, 1986.     

Pressure of the lateral surface of a cylinder on a periodically layered half space

We consider a two-dimensional contact problem of indentation of an absolutely rigid cylinder into an inhomogeneous half space with periodic structure. The zone of periodicity consists of two homogeneous elastic layers. The solution of the classical problem of the theory of elasticity is compared with the solution of the problem in which the inhomogeneous half space is replaced by a homogenized space. We propose simple engineering formulas for the evaluation of contact characteristics (the width of the contact zone and the distribution of contact pressure) approximating the solution of the problem in the case where the homogenized medium inadequately models the inhomogeneous medium. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 3, pp. 51–57, May–June, 2007.     

Three-dimensional vortex flow field around a circular cylinder in a quasi-equilibrium scour hole

The three-dimensional flow field around a circular cylinder in a quasi-equilibrium scour hole under a clear water regime has been investigated experimentally. The distribution patterns of tangential, radial and vertical components of velocity upstream and longitudinal component of velocity downstream of a cylinder have been presented in this paper. The flow simulation results show the existence of a helical motion of fluid around the cylinder.     

Certain features of transverse flow about a cylinder with longitudinal ribs

It was experimentally established that the structure of the boundary-layer separation and the flow regime preceding separation can be influenced, by installing longitudinal ribs on the surface over which flow is occurring.     

Viscous-fluid flow in a thin layer on the side surface of a rotating braking-upper-end cylinder

An analytical solution is obtained to the hydrodynamic problem on circulating viscous-fluid flow in a thin layer on the side surface of a rotating braking-end cylinder. Calculated data are in satisfactory agreement with the experimental findings and with the numerical integration of the equations of motion.Moscow Engineering Physics Institute. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 6, pp. 814–840, June, 1992.     

Effect of viscosity on the vortex structure of a flow around a cylinder and the drag of the cylinder with and without a disk in front of it

Large-scale vortex structures appearing in a flow around a cylinder with and without a disk for Reynolds numbers from 40 to 2500 are studied numerically and experimentally.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 2, pp. 224–232, August, 1986.     

Development and movement of vortex structures near the surface of a solid wall

The dynamics of large-scale vortices near the surface of a plate is modeled on the basis of numerical integration of nonsteady two-dimensional Navier-Stokes equations.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 6, pp. 900–909, June, 1989.     

Numerical simulation of laminar flow round a cylinder with passive and active vortex cells

Effects involving a reduction in the drag coefficient of a cylinder with passive and active vortex cells of different geometry are analyzed by solving the Navier-Stokes equations by a factorized finite-volume method using the concept of decomposition of the calculation region and using multilevel meshes. Pis’ma Zh. Tekh. Fiz. 24, 33–41 (April 26, 1998)     

An experimental investigation of liquid metal flow past a cylinder in longitudinal magnetic field

The distribution of pressure on the surface of a cylinder is obtained as a result of experimental investigation; this distribution significantly varies with increasing magnetic induction compared to the flow past a cylinder in the absence of magnetic field. In so doing, the pressure drag coefficient of the cylinder significantly increases. The measurements of velocity profiles reveal that the extent of the region of stagnant flow before the cylinder (the so-called “leading” wake) increases with magnetic induction. The dependence of axial defect of velocity on the MHD interaction parameter is obtained; this dependence under conditions of flow in a strong magnetic field is unaffected by the shape of the body subjected to flow, as is confirmed by the results of experiment involving the flow past a plate.     

Diffraction of cylinders with longitudinal surface structures

We present a model to determine the light scattered by a metallic cylinder with longitudinal structures when the cylinder is illuminated by a Gaussian light beam in oblique incidence. The model is based on an approximate solution to the Helmholtz-Kirchhoff integral by means of the stationary-phase method. We have studied the variations of the diffraction pattern in terms of the size of the defect and other geometrical parameters. The width of the beam and the misalignment between the beam and the cylinder have also been considered, as well as the optical properties of the surface.     

Computation of the dynamics of swirling vortex flow in a cylinder of an internal-combustion engine during the compression stroke

The vortex flow configuration in an engine cylinder is calculated for various geometries of an undivided combustion chamber. The data of a numerical analysis and experimental measurements are compared.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 4, pp. 654–660, October, 1986.     

A note on the flow in a trailing vortex

Summary We show that if the equations governing the fluid motion in a trailing vortex is linearized as by Batchelor, more than one solution can be constructed. Within the framework of the linear theory, there is no criterion to determine which solution is to be used. To clarify the situation, we formulate the Navier-Stokes equations in parabolic coordinates and seek asymptotic solutions valid far downstream. By insisting that the interaction of the swirl with the uniform stream be a first order effect, we obtain the first two terms in the asymptotic expansions for the Stokes stream function and the angular momentum. The result thus obtained differs from that given by Batchelor in that the axial velocity defect decays algebraically.On leave from Department of Mathematics, McGill University, Montreal 110, Quebec, Canada.     

Similarity of plasmatron characteristics for longitudinal vortex flow around the arc with variations in the gas flow rate

The volt-ampere charateristics (VAC) of an elecric arc are correlated with longitudinal vortex air and nitrogen flows in plasmatrons with a rod-like cathode and two tubular electrodes. Two types of exponent approximations are used: a simple empirical formula and a relationship between generalized variables. It is shown by methods of regression analysis that the use of generalized variables provides similarity of the VAC upon variations in the gas-flow rate.Translated from Inzhenerno Fizicheskii Zhurnal, Vol. 68, No. 6, pp. 943–948, 1995.     

Unsteady MHD-boundary-layer of a source and vortex flow adjacent to a stationary surface

Summary The steady laminar incompressible flow of an electrically conducting fluid over an infinite permeable disk in the presence of an axial magnetic field has been investigated, and a self-similar solution of the boundary-layer equations is obtained numerically. For large values of the suction parameter, a closed form solution is obtained. Also, an asymptotic solution is found for large values of the independent variable. The surface-shear stresses in the radial and tangential directions and the surface heat transfer strongly depend on the suction parameter, the ratio of the source and vortex flow and the magnetic field except the surface heat transfer which weakly depends on the magnetic field. The similarity solution of the boundary-layer equations exists only when a certain minimum suction or magnetic field is applied. The results of the analytical solution are in good agreement with those of the numerical solution for the suction parameterf _w3.     

催化裂化密闭快分系统封闭罩内流场优化

针对催化裂化密闭快分(CVQS)系统封闭罩内上方存在的非对称不稳定的旋涡流引起的压力不稳定现象,在一套大型冷模装置上,实验测定旋涡流出现的位置与操作条件间的时空特性;为消除不稳定旋涡流,在封闭罩内添加直板形式的导流板,与不添加导流板的装置进行实验对比。结果表明,装置加入合适导流板后,封闭罩内的流场得到改善,有效消除旋涡流现象,减弱了压力波动,使系统的压降明显减小。     

Stationary heat conduction in cylinder with piecewise-constant coefficient of heat exchange on lateral surface

The reduction to infinite systems is extended to the case of boundary conditions of the third kind. A particular case of a portion of the lateral surface of a cylinder being thermally insulated is investigated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 29, No. 2, pp. 345–351, August, 1975.