二维湍流气固两相射流的数值模拟

本文采用两相湍流的Ｋ－ε模型和颗粒湍流扩散的Ｐｅｓｋｉｎ公式，对含有相同尺寸的球状颗粒的圆截面湍流射液进行了数值分析。计算采用对抛物型方程的推进求解技巧。研究了两种不同的阻力系娄公式对两相湍射流的影响。一个阻力系数公式是由谢定国和周红字最近推导出来的，它反映了颗粒体积率和阻力的影响，另一阻力系数公式是Ｃｌｉｆｔ等人根据颗粒球的标准实验阻力曲线推导出来的，计算结果和实验进行了比较。结果表明，谢一周阻     

NUMERICAL SIMULATION OF TURBULENT FLOW CHARACTERISTICS IN A CURVED PIPE WITH A BAFFLE

A numerical study on the characteristics of developing turbulent flow in a curved pipe with a baffle was carried out in body-fitted coordinates with the k-ε model turbulence. A curved duct of square cross-section was examined first, and the results agree very well with the experimental data. Then two kinds of pipes, a normal curved pipe and that with a baffle were studied. The computational results are presented and compared with each other to illustrate the changes of the flow after adding the baffle. The longitudinal velocity in the pipe with a baffle was characterized by outer velocity bigger than the inner one. The secondary flow was characterized by four-vortex structure with the intensity reduced, which results in the equability of the flow field of the cross-section compared with that without a baffle, and has much more significant meaning in engineering.     

NUMERICAL SIMULATION OF TURBULENT JETS WITH LATERAL INJECTION INTO A CROSSFLOW

1. INTRODUCTION The interaction of jets with crossflow generates complex flow fields which exist in a variety of industrial applications, e.g. internal film cooling of turbine blades, dilution air jets in combustion chambers, jet from V/STOL aircraft in transition flight. Systematic experimental, theoretical and numerical investigations of the flow fields began several decades ago, where the parameters studied include the jet injection angel, the jet-to-crossflow velocity ratio, the jet …     

THE NUMERICAL COMPUTATION OF TURBULENT FLOW IN TEE-JUNCTION

A numerical model for calculating the turbulent flow in tee-junction is given in thispaper.The calculations are performed using a finite-difference procedure,and turbulence is ac-counted for by using a two-equation k-ε model of turbulence.Results,consisting of mean veloci-ty profiles and pressure losses due to the junction,have been obtained,and show that the flowsituation in tee-junction is very complex.The computed results agree closely with the experimen-tal data and validate that the present model is reasonable and the numerical calculations are suc-cessful.     

NUMERICAL SIMULATION OF THE TURBULENT FLOW IN ROTATING DUCT

l.INrnODUCT1oNFlowintherotatingductisakindofphenomenonofturbulentflow,whichisoftenfoundintheengineeringapplications,suchasinthecentrifugalcompressor,centrifugalpumpandturbomachinery.Theinvestigationontheductflowisveryimportantfortheen-gineeringpracticejustasthequalityofflowintheductmakesbiginfluenceontheperfor-manceandefficiencyofthemachine.Thestudyontheflowintherotatingductbeganin6os'.JohnsonL1jmeasuredthevelocityofthemainstreaminthetwodimensionalrotatingduct.Comparedwiththeflowinthestati…     

LARGE EDDY SIMULATION OF PARTICLE TRANSPORT IN FULLY DEVELOPED VERTICAL TURBULENT CHANNEL FLOW

Fully developed vertical turbulent channel flow with particle transport was investigated by use of Large Eddy Simulation (LES) approach coupled with dynamic the SubGrid Scale (SGS) model. It was assumed that the motion of each particle is followed in a Lagrangian frame of reference driven by the forces exerted by fluid motion and gravity under the condition of one-way coupling. The goal of this study is to investigate the effectiveness of the I.ES technique for predicting particle transport in turbulent flow and the behavior of particle-laden turbulent channel flow for three kinds of particles at different Stokes numbers. To depict the behavior of particle-laden turbulent channel flow, statistical quantities including particle fluctuation and fluid-particle velocity correlation, and visualization of the particle number density field were analyzed.     

DIRECT NUMERICAL SIMULATION OF TURBULENT FLOW IN A STRAIGHT SQUARE DUCT AT REYNOLDS NUMBER 600

This article presents the direct numerical simulation results of the turbulent flow in a straight square duct at a Reynolds number of 600, based on the duct width and the mean wall-shear velocity. The turbulence statistics along the wall bisector is examined with the turbulent flow field properties given by streamwise velocity and vorticity fields in the duct cross section. It was found that the solutions of the turbulent duct flow obtained in a spatial resolution with 1.2×10⁶ grid points are satisfactory as compared to the existing numerical and experimental results. The results indicate that it is reasonable to neglect the sub-grid scale models in this spatial resolution level for the duct flow at the particular friction Reynolds number.     

EFFECT OF NON-SPHERICAL PARTICLES ON THE FLUID TURBULENCE IN A PARTICULATE PIPE FLOW

In the non-spherical particulate turbulent flows,a set of new fluid fluctuating velocity equations with the nonspherical particle source term were derived, then a new method,which treats the slowly varying functions and rapidly varying functions separately, was proposed to solve the equations, and finally the turbulent intensity and the Reynolds stress of the fluid were obtained by calculating the fluctuating velocity statistically. The equations and method were used to a particulate turbulent pipe flow. The results show that the turbulent intensity and the Reynolds stress are decreased almost inverse proportionally to the fluctuating velocity ratio of particle to fluid. Nonspherical particles have a greater suppressing effect on the turbulence than the spherical particles. The particles with short relaxation time reduce the turbulence intensity of fluid, while the particles with long relaxation time increase the turbulence intensity of fluid. For fixed particle and fluid, the small particles suppress the turbulence and the large particles increase the turbulence.     

NUMERICAL SIMULATION OF 3-D TURBULENT FLOWS IN A CUT-OFF VALVE AND ANALYSIS OF FLOW CHARACTERISTICS IN PIPE

1 .　INTRODUCTIONThevalvehasbeenplayinganimportantroleinthe pipeengineeringandisalsooneofmaincomponentsgeneratingtheheadloss .Becauseofthecomplexgeometry ,thedesignwasusuallyeval uatedempiricallyinthepast,whichcausesmuchenergyloss .Toreducetheenergyloss ,itisessen tialforadesignertoknowthedetailsofflowfieldinthevalvepipe .Recently ,withtheremarkableprogressintheComputationalFluidDynamics(CFD)andcomputerhardware ,itisexpectedthatCFDwillbecomeapowerfultoolinthedesignofvalve .Intheactual…     

INVESTIGATION OF THE MEAN-FLOW SCALING AND TRIPPING EFFECT ON FULLY DEVELOPED TURBULENT PIPE FLOW

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＡｘｉｓｙｍｍｅｔｒｉｃｆｕｌｌｙｄｅｖｅｌｏｐｅｄｔｕｒｂｕｌｅｎｃｅｉｎｐｉｐｅｆｌｏｗｐｒｏｖｉｄｅｓｏｎｅｏｆｔｈｅｓｉｍｐｌｅｓｔａｎｄｍｏｓｔｒｅ ｐｒｏｄｕｃｉｂｌｅｌａｂｏｒａｔｏｒｙｆｌｏｗｓｆｏｒｅｘｐｅｒｉｍｅｎｔａｌｗａｌｌｔｕｒｂｕｌｅｎｃｅｓｔｕｄｉｅｓ,ａｎｄｏｗｉｎｇｔｏｉｔｓｃａｌｃｕｌａｔｉｏｎｐｏｓｓｉｂｉｔｉｅｓ,ｉｓｏｆｇｒｅａｔｉｎｔｅｒｅｓｔｔｏｒｅｓｅａｒｃｈｅｒｓ .Ｉｎｔｈｅｍｏｒｅｔｈａｎｈａｌｆａｃｅｎｔｕｒｙｓｉｎ…     

STUDY ON FLOWS THROUGH CENTRIFUGAL PUMP IMPELLER BY TURBULENT SIMULATION

A finite volume numerical method is presented for simulating internal tur-bulent flows on the blade-to-blade surface through a centrifugal pump impeller, in which, a mesh in body-fitted coordinates is generated for the computation. In detail, the SIM-PLEC algorithm is utilized for solving governing equations of incompressible viscous/turbulent flows through the pump impeller. The K-ε turbulence model is adopted to describe the turbulent flow process. Some worthwhile simulated results are presented.     

DIRECT NUMERICAL SIMULATIONS OF THE DYNAMICS OF PARTICLES WITH ARBITRARY SHAPES IN SHEAR FLOWS

A fluid-structure interaction method based on the arbitrary Lagrangian-Eulerian method and a dynamic mesh method was developed to simulate the dynamics of a rigid particle in shear flows. In the method, the governing equations for the fluid flow and particle motion were sequentially solved in a two-way coupling fashion. The mesh system was deformed or re-meshed by the dynamic mesh method. The method was employed to simulate the dynamics of a single particle suspended in a flow channel and the dynamics of the particle were studied. The simulation results show that the angular velocity is not only a function of the inclination angle, is but also influenced by the aspect ratio yielding a hysteresis, while the angular velocity obtained from the Keller-Scalak model is a function only of the inclination angle and does not show a hysteresis. The present simulations clearly demonstrate that the Fluid-Structure Interaction (FSI) module is very stable, accurate and robust.     

AN INVESTIGATION OF TURBULENT HEAT TRANSFER IN CHANNEL FLOWS BY LARGE EDDY SIMULATION

Large Eddy Simulation (LES) of fully developed turbulent channel flow with heat transfer was performed to investigate the effects of the Reynolds number on the turbulence behavior. In the present study, the bottom wall of the channel was cooled and the top wall was heated. The Reynolds numbers, based on the central mean-velocity and the half-width of the channel, were chosen as 4000, 6000, 104 and 2×104, and the Prandtl number as 1.0. To validate our calculations, the present results were compared with available data obtained by Direct Numerical Simulation (DNS), which proves to be in good agreement with each other. To reveal the effects of the Reynolds number, some typical quantities, including the velocity fluctuations, temperature fluctuation, heat fluxes and turbulent Prandtl number, were studied.     

NUMERICAL PREDICTION OF LINE BUOYANT JETS IN CROSS FLOWS

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＡｂｕｏｙａｎｔｊｅｔｉｓｄｅｆｉｎｅｄａｓａｓｏｕｒｃｅｏｆｂｕｏｙａｎｔｆｌｕｘａｎｄｉｎｉｔｉａｌｍｏｍｅｎｔｕｍｏｒｖｏｌｕｍｅｆｌｕｘｅｓ .Ｌｏｎｇｍｕｌｔｉｐｏｒｔｏｃｅａｎｓｅｗｅｒｔｈｅｏｕｔｆａｌｌｄｉｆｆｕｓｅｒｓｃａｎｂｅａｌｗａｙｓａｐｐｒｏｘｉｍａｔｅｄａｓｔｗｏ ｄｉｍｅｎｓｉｏｎａｌｌｉｎｅｂｕｏｙａｎｔｊｅｔｓ .Ｂｕｔｆｏｒｔｈｅｌｉｎｅｂｕｏｙａｎｔｊｅｔｓｏｆｆｉｎｉｔｅｌｅｎｇｔｈ ,ｔｈｅｄｉｓｐｅｒｓｉｏｎｏｆｔｈｅｄｉｓｃｈａ…     

DIRECT NUMERICAL SIMULATION OF PARTICULATE FLOWS

1 .　INTRODUCTIONParticulateflowsofsolidsinfluidshavebeenwidelyusedfordifferentpurposesinindustry ,suchassedimentingandfluidizedsuspensions ,lubricat edtransportandhydraulicfracturingofhyfrocar bonreservoirs,etc .Inthepast,particulateflowswithmany particlesaremostlynumericallysimu latedusingapproximatemethods ,whichincludesimulationsbasedonthepotentialflow ,theStokesflow ,and point particleapproximations[1] .Thecomputationsareallsimplifyiedbyignoringsomepossiblyimportanteffects .Thedistri…     

NUMERICAL SIMULATION OF 3-D TURBULENT FLOW IN THE MULTI- INTAKES SUMP OF THE PUMP STATION

In this article, a numerical model for three-dimensional turbulent flow in the sump of the pump station was presented. A reasonable boundary condition for the flow in the sump with several water intakes at different flow rates was proposed. The finite volume method was employed to solve the governing equations with the body fitted grid generated by the multi-block grid technique. By using the Fluent software, the fluid flow in a model sump of the pump station was calculated. Compared with the experimental result, the numerical result of the example is fairly good.     

NUMERICAL SIMULATION OF STRESS-INDUCED SECONDARY FLOWS WITH HYBRID FINITE ANALYTIC METHOD

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｔｕｒｂｕｌｅｎｔｓｔｒｕｃｔｕｒｅｓｉｎｎｏｎ ｃｉｒｃｕｌａｒｄｕｃｔｓａｎｄｏｐｅｎｃｈａｎｎｅｌｓａｒｅｃｈａｒａｃｔｅｒｉｚｅｄｂｙｌｏｎｇｉｔｕｄｉ ｎａｌｖｏｒｔｉｃｅｓ .Ｔｈｅｓｅｖｏｒｔｉｃｅｓａｒｅｔｈ     

THREE-DIMENSIONAL NUMERICAL SIMULATION OF BOD-DO FOR LARGE RESERVOIR

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＢｅｃａｕｓｅｔｈｅｒｅａｒｅｍａｎｙｂｕｉｌｔａｎｄｂｕｉｌｄｉｎｇｌａｒｇｅｄｅｅｐｒｅｓｅｒｖｏｉｒｓｉｎＣｈｉｎａ ,ｔｈｅｓｔｕｄｙｏｆｔｈｅｍｏｄｅｌｏｆＢｉ ｏｌｏｇｉｃａｌＯｘｙｇｅｎＤｅｍａｎｄ (ＢＯＤ)ａｎｄＤ     

NUMERICAL SIMULATION OF TURBULENT SPOTS IN INCLINED OPEN-CHANNEL FLOW

The generation and evolution of turbulent spots in the open-channel flow are simulated numerically by using the Navier-Stokes equations. An effective numerical method with high accuracy and high resolution is developed.The fourth order time splitting methods with high accuracy is proposed. Thre-dimensional coupling difference methods are presented for the spatial discretization of the Poisson equation of pressure and Hemholtz equations of velocity, therefore, the fourth-order thre-dimensional coupling central difference schemes are constituted. The fourth-order explicit upwind-biased compact difference schemes are designed to overcome the difficulty for the general higher-order central differences cheme which is inadaptable in the boundary neighborhood.The iterative algorithm and overall time marching is used to enhance efficiency. The method is applied in the numerical simulation of turbulent spots at various complex boundary conditions and flow domains. The generation and the developing process of turbulent spots are given, and the basic char acteristics of turbulent spots are shown by simulating the evolution of the wall pulse in inclined open-channel flow.     

TURBULENT BOUNDARY LAYER DEVELOPMENT IN THE ENTRANCE REGION OF A SMOOTH ROUND PIPE

The study of the turbulent boundary layer along a smooth round pipe is of greatsignificance both in practice and in theory.In this paper,the formulae for calculating the tur-bulent boundary layer thickness are obtained by solving the momentum integral equation of theboundary layer in which the assumptions of the logarithmic law and exponential law of velocitydistribution are adopted.The methods for calculating the mean flow velocity in the developingregion of turbulent boundary layer in a round pipe are proposed.The relation between the expo-nent n and the factor μ·δ/ν is studied and a formula for calculating the exponent n is obtained.