Plane Turbulent Couette Flow

The problem on plane turbulent Couette flow for an incompressible liquid has been solved based on the anisotropicturbulence model.     

Numerical Calculation of the Turbulent Flow of a Gas Suspension in a Tube

A mathematical model for describing the turbulent flow of a gas suspension in a tube has been formulated within the framework of the combined Euler–Lagrange approach. Results of calculations by this model are in good agreement with theoretical data obtained using the continuous model developed by the authors [Teplofizika Aéromekhanika, No. 1, 5?–71 (1999)]. The importance of detailed modeling of the turbulent structure of the carrying medium in the near‐wall zone has been shown based on a comparative analysis of computational and experimental data.     

Flow Instability of Molten GaAs in the Czochralski Configuration

The flow and heat transfer of molten GaAs under the interaction of buoyancy, Marangoni and crystal rotation in the Czochralski configuration are numerically studied by using a time-dependent and three-dimensional turbulent flow model for the first time. The transition from axisymmetric flow to non-axisymmetric flow and then returning to axisymmetric flow again with increasing centrifugal and coriolis forces by increasing the crystal rotation rate was numerically observed. The origin of the transition to non-axisymmetric flow has been proved to be baroclinic instability. Several important characteristics of baroclinic instability in the CZ GaAs melt have been predicted. These characteristics are found to be in agreement with experimental observations.     

Boundary Layer Flow on a Model Propeller

Flash photographs have been made of a model screw propeller under test in a towing tank, to show the areas of laminar and turbulent flow in the boundary layers over the blades. These areas may be defined from the surface patterns made by ejecting a liquid dye from fine holes in the rotating blade, and the change in extent of each region with change of Reynolds number is coupled with the scale effect evident in model tests.     

Suppressing a Laminar Flow Separation Zone by Spark Discharge at Mach Number M = 1.43

The influence of flow perturbations generated by an electric discharge on the region of interaction between a shock wave and laminar boundary layer in the flow on a flat plate at a Mach number of M = 1.43 has been experimentally studied. The oblique shock wave generated by a wedge mounted above the plate induced separation of the flow, while perturbations in the flow were introduced by a spark discharge on the model plate surface. It is established that the discharge leads to the formation of turbulent and thermal spots. The turbulent spot suppresses the separation zone, while the thermal spot leads to a local increase in the boundary layer thickness in the interaction zone.

     

Heat Transfer in a Turbulent Flow of Gas in a Tube under Conditions of Resonance Oscillation of the Flow Rate

A prediction study is made into the heat transfer in a turbulent flow of gas (air) in a narrow tube with superimposed resonance oscillation. The model of turbulent transfer includes the effect of nonstationarity on the turbulent stress and heat flux. The finite difference method is used to solve the equations of motion and energy. The distribution of the flow rate and pressure along the tube is found by way of numerical solution of a set of cross section-averaged nonstationary equations of motion, continuity, and energy. The effect of the process parameters (Reynolds number, dimensionless oscillation frequency, thermal boundary conditions on the wall) on the period-average heat transfer and heat flux to the wall is analyzed.     

Numerical Simulation of Nonstationary Turbulent Flow around an Automobile Profile Near a Mobile Screen

A numerical investigation of nonstationary turbulent flow of an incompressible viscous fluid around the profile of a Volkswagen automobile near a mobile screen has been carried out on the basis of solution of the Reynolds equations closed using a two-parameter dissipation model of turbulence by the finite-volume method.     

Gravity Separation of Particulate Solids in Turbulent Fluid Flow

The separation characteristics of particles’ settling velocity, size, density, and shape are introduced, and the equivalent settling condition for laminar, transition, and turbulent flow are explained. A similarity model of particle transport in a turbulent flow field is briefly discussed. Typical operation principles in separation devices for counter current and cross-flow separation are presented. The separation function, cut point, sharpness, and separation stage utilization coefficient are determined to assess the efficiency for process sequences for multistage turbulent cross-flow separation. Satisfactory to very good results were achieved in the difficult separation of a partially liberated aggregate consisting of hardened cement paste rubble with sharpness from 0.66 to 0.94 at separation stage utilization coefficients of 7 to 87%. Specific mass flow rates of 3 to 16 t/(m² · h) and mass related energy consumption of 0.2 to 8 kWh/t were obtained.     

Gravity Separation of Particulate Solids in Turbulent Fluid Flow

The separation characteristics of particles' settling velocity, size, density, and shape are introduced, and the equivalent settling condition for laminar, transition, and turbulent flow are explained. A similarity model of particle transport in a turbulent flow field is briefly discussed. Typical operation principles in separation devices for counter current and cross-flow separation are presented. The separation function, cut point, sharpness, and separation stage utilization coefficient are determined to assess the efficiency for process sequences for multistage turbulent cross-flow separation. Satisfactory to very good results were achieved in the difficult separation of a partially liberated aggregate consisting of hardened cement paste rubble with sharpness from 0.66 to 0.94 at separation stage utilization coefficients of 7 to 87%. Specific mass flow rates of 3 to 16 t/(m² · h) and mass related energy consumption of 0.2 to 8 kWh/t were obtained.     

基于蜂群算法的等压灌装阀阀口流道结构优化

目的为了改善等压灌装阀的灌装性能,分析阀口流道结构参数对液料流场的影响,求解流道内最大压力损失、最大液料流速和最大湍动能均最小化的约束多目标优化问题。方法基于正交试验设计和Fluent流场仿真软件对灌装阀阀口流道流场进行数值模拟,并通过回归分析建立以阀口流道结构参数为自变量的最大压力损失、最大液料流速和最大湍动能的经验方程,进而建立阀口流道结构参数约束多目标优化模型,采用约束多目标人工蜂群算法对优化模型进行求解。结果流道内最大压力损失最小化、最大液料流速最小化和最大湍动能最小化这3个目标之间存在冲突,无法同时达到最优,基于多目标人工蜂群算法获得了阀口流道结构参数的最优Pareto解集。结论约束多目标人工蜂群算法能有效用于等压灌装阀阀口流道结构参数的优化。     

Pulsating Turbulent Flow of Gas in a Round Pipe

An analysis is performed of the presently available results of experimental and prediction studies into pulsating turbulent flow of liquid in a narrow pipe under conditions when the compressibility is apparent. It is demonstrated that the simulation of such flows in the general case may be performed only numerically, using a model of turbulence that adequately includes the effect of oscillation on turbulent transfer. Use is made of a model of turbulence whose validity is proved by comparing the calculation and experimental results for a wide range of flows. Calculations are performed for a pulsating flow of gas in pipes with isothermal and adiabatic walls, acoustically closed at the outlet, in the frequency range corresponding to the first resonance harmonic. The predicted variations of the heat flux to the wall and of the hydraulic drag, averaged over the oscillation period, as functions of the process parameters such as the Reynolds number of the mean flow and the dimensionless oscillation frequency are discussed.     

Simulation of Turbulent Flow Past Bluff Bodies on Coarse Meshes Using General Galerkin Methods: Drag Crisis and Turbulent Euler Solutions

In recent years adaptive stabilized finite element methods, here referred to as General Galerkin (G2) methods, have been developed as a general methodology for the computation of mean value output in turbulent flow. In earlier work, in the setting of bluff body flow, the use of no slip boundary conditions has been shown to accurately capture the separation from a laminar boundary layer, in a number of benchmark problems. In this paper we extend the G2 method to problems with turbulent boundary layers, by including a simple wall-model in the form of a friction boundary condition, to account for the skin friction of the unresolved turbulent boundary layer. In particular, we use G2 to simulate drag crisis for a circular cylinder, by adjusting the friction parameter to match experimental results. By letting the Reynolds number go to infinity and the skin friction go to zero, we get a G2 method for the Euler equations with slip boundary conditions, which we here refer to as an EG2 method. The only parameter in the EG2 method is the discretization parameter, and we present computational results indicating that EG2 may be used to model very high Reynolds numbers flow, such as geophysical flow.     

Numerical Simulation of Fluid Flow and Mixing in Gas-Stirred Ladles

In this work air injection into a water physical model of an industrial steel ladle was simulated. Calculations were developed based on a multiphase Eulerian fluid flow model involving principles of conservation of mass, momentum, and chemical species for both phases to predict turbulent flow patterns and mixing times for centric and eccentric injections. Effects of gas flow rate, injector position, number of injectors, and geometry of ladle on mixing time were analyzed. Optimum injection conditions are: single injector at 2/3 of radius and high gas flow rates. Quantitative correlation of mixing time as a function of main process variables was obtained.     

CFD在空调室内气流组织设计中的应用

本文采用k-ε模型计算了三维室内空气湍流流场,提出进行空调室内气流组织设计时,在初步计算的基础上,用数值分析的方法模拟各种工况下室内气流的温度场、速度场,得到最优的设计方案.研究结果表明,采用CFD进行室内气流的模拟计算,可以预测各种工况下室内气流的温度、速度分布,从而达到优化设计方案的目的.     

Simulation of fine-dispersed turbulent flow in a pipe on the basis of the nonlinear model of turbulent viscosity

A nonlinear model of turbulent viscosity (the explicit algebraic Reynolds stress model) for gas-dispersed flow with small heavy particles has been presented. The calculations have been checked by comparison with the experimental data on the effect of the fine-dispersed admixture on turbulent flow of air in a pipe.     

A Model for the Prediction of Concentration and Particle Size Distribution for the Flow of Multisized Particulate Suspensions through Closed Ducts and Open Channels

The model proposed by Karabelas has been modified for the prediction of solid concentration and particle size distributions for the flow of multi size particulate slurries through pipe, 2-D duct, and open channel. The experimental data reported in the literature have been used to establish the limitations of the Karabelas model. Based on extensive analysis of the experimental data, modifications have been proposed in the model to overcome the deficiencies. In particular, the effect of solid concentration on particle settling and turbulent diffusivity has been incorporated into the modified model. The modified model predicts the solid concentration and particle size distribution with reasonable accuracy for all the geometries considered.     

A Model for the Prediction of Concentration and Particle Size Distribution for the Flow of Multisized Particulate Suspensions through Closed Ducts and Open Channels

The model proposed by Karabelas has been modified for the prediction of solid concentration and particle size distributions for the flow of multi size particulate slurries through pipe, 2-D duct, and open channel. The experimental data reported in the literature have been used to establish the limitations of the Karabelas model. Based on extensive analysis of the experimental data, modifications have been proposed in the model to overcome the deficiencies. In particular, the effect of solid concentration on particle settling and turbulent diffusivity has been incorporated into the modified model. The modified model predicts the solid concentration and particle size distribution with reasonable accuracy for all the geometries considered.     

共振式消声器气流再生噪声分析

为研究汽车共振式排气消声器气流再生噪声与气流速度和温度的关系,利用大涡模拟(LES)湍流模型与声类比(AA)方法,建立了消声器流场和声场模型,搭建实验台并验证了模型的正确性。在此基础上,分析了流噪声和湍动能。结果表明:在消声器的结构突变处,流体噪声源和湍动能均较大,云图分布具有一致性。消声器气流再生噪声以3 000 Hz以下为主,噪声值随着进口流速的增大而增大,随着气流温度的增大而减小,但频谱特性受流速和温度的影响较小。消声器多场耦合下的气流再生噪声研究结果可为消声器设计提供一定参考。     

Numerical Simulation of Two-Phase Flow in a Tornado Funnel

The model of flow in a tornado funnel previously suggested in [1] is updated. The updating of the flow model involves the inclusion of the processes of volume condensation of water vapor. The notation for the input equations is suggested, which is convenient from the standpoint of numerical simulation of processes of heat and mass transfer with due regard for the condensation of moisture within the tornado funnel. The results are given of numerical simulation of two-phase turbulent heat and mass transfer within a tornado funnel. The obtained numerical distributions enable one to identify the range of problem parameters in the case of which an upward flow of moist air may arise, which is sufficient to maintain a quasistationary motion of the tornado.