Inertial phase separation in rotating self-gravitating media

The centrifugal separation of foreign inclusions (particles) in a rotating spherical volume of a self-gravitating medium is considered in the hydrodynamic approximation. Using the full Lagrangian approach, the particle trajectories and radial concentration profiles are studied for a rigid-body velocity distribution in the carrier phase. The regimes of continuum and free-molecular flow around the particles are considered. The cases of a heavy (with density greater than that of the carrier phase and traveling toward the center) and a light-weight (traveling toward the periphery) admixture are investigated. Analytical and numerical solutions corresponding to steady-state spherically symmetric boundary conditions for the dispersed phase are found. It is shown that the presence of rotation may result in a significant angular anisotropy of the radial particle concentration distributions and, in particular, in the formation of ring-shaped accumulation zones of heavy inclusions in the equatorial plane. The solutions obtained can be used to explain the mechanisms of onset of density nonuniformities in planet cores, the formation of planetary systems from gas-particle clouds, and the behavior of aerosol particles in atmospheric vortices.Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, 2004, pp. 86–100.Original Russian Text Copyright © 2004 by Ahuja, Belonoshko, Johansson, and Osiptsov.     

环形通道内湍流旋流流动的数值模拟

本文应用一种考虑湍流－旋流相互作用及湍流脉动各向异性的新的代数Ｒｅｙｎｏｌｄｓ应力模型,对环形通道内的湍流旋流流动进行了数值模拟,研究了改主为旋流流数,进口轴向速度及半径比等参数对环形通道内湍流流动的影响,以及对强化环形通道内传热的作用。     

Application of PDF Modeling to Swirling and Nonswirling Turbulent Jets

The turbulence modeling in probability density function (PDF) methods is studied through applications to turbulent swirling and nonswirling co-axial jets and to the temporal shear layer. The PDF models are formulated at the level of either the joint PDF of velocity and turbulent frequency or the joint PDF of velocity, wave vector, and turbulent frequency. The methodology of wave vector models (WVMs) is based on an exact representation of rapidly distorted homogeneous turbulence, and several models are constructed in a previous paper [1]. A revision to a previously presented conditional-mean turbulent frequency model [2] is constructed to improve the numerical implementation of the model for inhomogeneous turbulent flows. A pressure transport model is also implemented in conjunction with several velocity models. The complete model yields good comparisons with available experimental data for a low swirl case. The individual models are also assessed in terms of their significance to an accurate solution of the co-axial jets, and a comparison is made to a similar assessment for the temporal shear layer. The crucial factor in determining the quality of the co-axial jet simulations is demonstrated to be the proper specification of a parameter ratio in the modeled source of turbulent frequency. The parameter specification is also shown to be significant in the temporal shear layer.     

On problems of optimal design of shallow shell with double curvature on elastic foundation

The present paper discusses a method of optimal design of the shallow shell with double curvature on the elastic foundation Substantially we take the initial flexural function as the control function or design variable which will be found and the potential energy of the external loads as the criterion of quality of the optimal design of the shallow shell with double curvature, therefore the functional of the potential energy will be aim function. The optimal conditions and the isoperimetric conditions belong to the constrained conditions. thus we obtain the necessary conditions of the optimal design for the given problems, at the same time the conjugate function is introduced, then the problems are reduced to the solutions of two boundary value problems for the differential equation of conjugate function and the initial flexual function.     

Free bending vibration of circular column partially submerged in water

In this paper, the author studied the bending vibration of circular column partially submerged in water.An equation of frequency and an exact solution of corresponding function of vibrational modes are given. It points out that the effect of water is equivalent to an attached distributive mass Therefore the frequency with water is lower than that without water     

旋流和无旋突扩流动的LES和RANS模拟

本文用smagorinsky-Lilly亚网格尺度湍流模型对旋流突扩流动(s=0.53)和无旋突扩流动(s=0)进行了大涡模拟(LES模拟),同时分别用压力应变项为IPCM和IPCM+Wall模型的雷诺应力方程模型进行了RANS模拟,和LES的统计结果对比。LES的统计结果与雷诺应力模型的模拟结果及实验对照表明,LES结果与实验结果的吻合比雷诺应力模型的好,说明所用的亚网格尺度湍流模型对旋流流动是适用的,LES结果是可信的。LES的瞬态结果揭示出在旋流作用下,流场中存在复杂的旋涡脱落现象。大涡结构极易破碎成小涡,而在无旋突扩流动的情况下,由于剪切的作用更强,大涡结构的尺寸和范围比旋流流动的要大。     

超音速分离管内部流动的二维数值模拟与分析

为了克服现有天然气脱水技术的不足,基于气体动力学和传热传质学理论提出了一种新型的天然气超音速分离管装置.介绍了其基本结构和分离机理,对装置内部流动进行了合理假设,建立了几何模型,并利用张量形式的时均方程组对其内部的稳态可压缩湍流流动进行了求解,结果发现在轴向-400 mm至-200 mm之间发生了激波现象,导致气流速度急剧下降,压力急剧上升,温度急剧上升.计算结果与之前的实验结果基本一致,为分离管几何结构优化提供了理论基础.     

旋流喷雾燃烧的直接数值模拟

对三维旋流喷雾燃烧进行了初步的直接数值模拟,其中液滴蒸发采用无限热传导蒸发模型描述,气相燃烧采用自适应单步反应机理,液滴的跟踪在拉格朗日框架中进行。模拟结果表明,喷雾燃烧的火焰结构十分复杂,仅采用传统的非预混燃烧模型是不够的。在蒸发和燃烧共存并存在强烈相互作用的区域,组分与混合物份额之间存在着复杂的关联,这给发展精确的湍流喷雾燃烧模型带来了挑战。     

LES of incompressible heat and fluid flows past a square cylinder at high Reynolds numbers

This paper presents large eddy simulation (LES) results of incompressible heat and fluid flows around a square cylinder (SC) at zero incident angle at high Reynolds numbers (Re) in the range from 1.25×10⁵ to 3.5×10⁵. LES results are obtained on the basis of swirling strength based sub-grid model, and a higher order upwind scheme developed with respect to the Taylor expansion. It was found that, for the zero incident SC wake flows at a Reynolds number in the range {Re₅ = Re/10⁵ ∈ [1.25, 3.5]}, the Strouhal number equals to 0.1079, completely independent of the Reynolds number; the coefficient of drag is around 1.835 with an uncertainty of about 1.9%, almost non-sensitive to the Re. When Re is beyond 3.0×10⁵, the time-averaged peak value of sub-grid viscosity is over 340, implying that the role of sub-grid model is crucial in some regions where vortex motion is active and vortex interaction is intense. The time–spanwise (t-z) averaged sub-grid viscosity ratio profiles and the profiles of fluctuations of the sub-grid viscosity ratio and velocity components at four locations downstream of the SC are presented. The fields of the t-z averaged sub-grid viscosity ratio, and the instantaneous fields of streamwise and spanwise vorticities are also reported and discussed. The predicted mean Nusselt number is compared with empirical correlations, revealing that swirling strength based LES has its potential in predicting natural and industrial flows.