PREDICTION OF TURBULENT FLOW CHARACTERISTICS IN THE CURVED DUCT WITH A BAFFLE

The changes of the developing turbulent flow characteristics in curved duct after adding a baffle are studied numerically at the body-fitted coordinates.a k-εmodel is used to represent the turbulence.a curved duct of rectangular cross-section is computed firstly, it has been observed that the predictions using the procedure agree very satisfactory with the experimental data.Then,two kinds of square ducts are studied,one is normal curved duct,the other is a duct with a baffle.The computational results are presented and compared to each other,in order to display the changes of the flow after adding a baffle in curved ducts.The secondary flow in a duct with a baffle is characterized by four-vortices structure with the outer two bigger than the inner two.Besides,compared with the duct without a baffle,the intensity of the secondary flows is reduced,which results in the flow field of the cross-section much more equable and has much more significant meaning in the engineering.     

NUMERICAL ANALYSIS OF THE FLUID FLOW IN A ROTATING CURVED ELLIPTICAL PIPE

A numerical study was conducted for the fully developed laminar flow in rotating curved elliptical pipe. Due to the rotation, the Coriolis force can also contribute to the secondary flow. The interaction of rotation and curvature complicates the flow characteristics. The boundary fitted coordinate was adopted to study the flow characteristic in the rotating systems. The effects of rotation on the flow transition were studied in detail. The generation and mergence of vortices in rotating curved elliptical pipes were also captured for the first time. The simulation results show that the flow for the case of large aspect ratio of the cross-section is more likely to be unstable than that for smaller one.     

THE FLOW IN ROTATING CURVED CIRCULAR PIPE

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｂｅｈａｖｉｏｒｏｆｔｈｅｆｌｕｉｄｉｎａｒｏｔａｔｉｎｇｃｕｒｖｅｄｐｉｐｅｉｓａｆｕｎｄａｍｅｎｔａｌａｎｄｍｕｃｈ ｓｔｕｄｉｅｄｐｒｏｂｌｅｍ .Ｔｈｅｒｅａｒｅｍａｎｙｅｎｇｉｎｅｅｒｉｎｇａｐｐｌｉｃａｔｉｏｎｓｏｆｔｈｉｓｒｏｔａｔｉｎｇｓｙｓｔｅｍ ,ｓｕｃｈａｓｇａｓｔｕｒ ｂｉｎｅｓ ,ｅｌｅｃｔｒｉｃｇｅｎｅｒａｔｏｒｓａｎｄｅｌｅｃｔｒｉｃｍｏｔｏｒｓ.Ｔｈｅｓｙｓｔｅｍｃａｎａｌｓｏｂｅｆｏｕｎｄｉｎｓｅｐａｒａｔｉｏｎｐｒｏｃｅｓｓ.Ｉｔｉｓ…     

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…     

NUMERICAL SIMULATION OF THE TURBULENT FLOW IN ROTATING DUCT

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

THE PERTURBATION SOLUTIONS OF THE FLOW IN A ROTATING CURVED ANNULAR PIPE

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＡｓａｎｉｎｔｅｒｅｓｔｉｎｇｆｕｎｄａｍｅｎｔａｌｐｒｏｂｌｅｍｉｎｆｌｕｉｄｍｅｃｈｎｉｃｓ,ｔｈｅｆｌｏｗｓｉｎｒｏｔａｔｉｎｇｃｕｒｖｅｄ ｐｉｐｅｓｗｉｔｈｃｉｒｃｕｌａｒｏｒｒｅｃｔａｎｇｕｌａｒｃｒｏｓｓ ｓｅｃｔｉｏｎｓｈａｖｅｂｅｅｎｓｔｕｄｉｅｄｂｙｎｕｍｅｒｏｕｓａｕｔｈｏｒｓ .Ｌｕｄｗｉｅｇ[1] ｉｓｔｈｅｆｉｒｓｔｒｅｓｅａｒｃｈｅｒｔｏａｎａｌｙｚｅｔｈｅｆｌｏｗｉｎａｒｏｔａｔｉｎｇｃｕｒｖｅｄｒｅｃｔａｎｇｕｌａｒｄｕｃｔａｎｄｄｅｖｅｌｏ…     

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.     

LAMINAR DEVELOPING FLOW IN THE ENTRANCE REGION OF ROTATING CURVED PIPES

1. INTRODUCTION The flow in rotating curved pipes with a constant circular cross-section have found wide applications in heat exchangers, piping systems, electric motors, chemical reactors and many other engineering systems. One of the principle features …     

FLOW AND HEAT TRANSFER OF OLDROYD-B FLUIDS IN A ROTATING CURVED PIPE

The flow and convected heat transfer of the Oldroyd-B fluids in a rotating curved pipe with circular cross-section were investigated by employing a perturbation method. A perturbation solution up to the second order was obtained for a small curvature ratio, κ. The variations of axial velocity distribution and secondary flow structure with F, Re and We were discussed in detail in order to investigate the combined effects of the three parameters on flow structure. The combined effects of the Coriolis force, inertia force and elastic force on the temperature distribution were also analyzed, which are greater than the adding independent effects of the three forces. The variations of the flow rate and Nusselt number with the rotation, inertia and elasticity were examined as well. The results show the characteristics of the heat and mass transfer of the Oldroyd-B fluids in a rotating curved pipe.     

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.     

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.     

UNSTEADY INTERMITTENT FLOW IN A ROTATING CURVED PIPE

The effects of rotation and intermittent frequency on the flow transition of secondary flow and. main flow were examined in detail. Certain hitherto unknown flow patterns were found. ,‘% numerical study was performed to study the characteristics of unsteady intermittent flow in a rorating curved pipe. Due to the rotation, both the Coriolis for ceand the centrifugal force could contribute to the unsteady intermittent flow and some complicated phenomena can be found. The results indicate that the unsteady intermittent floware mainly characterized by five parameters: the Dean number Dn, the curvature κ. the maximal force ratio F (of the Coriolis force to the centrifugal force in a cycle), the intermittent frequency parameter r/(the ratio of a pulslating time to the cycle period), and the Womersley number a. Present works shows the natures of the unsteady intermittent flow in a rotating curved pipe.     

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 …     

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.     

THREE-DIMENSIONAL NUMERICAL MODELING OF SECONDARY FLOWS IN A WIDE CURVED CHANNEL

Most natural rivers are curved channels, where the turbulent flows have a complex helical pattern, as has been extensively studied both numerically and experimentally. The helical flow structure in curved channels has an important bearing on sediment transport, riverbed evolution, and pollutant transport study. In this article, different turbulence closure schemes i.e., the mixing-length model and the k – ? model with different pressure solution techniques i. e., hydrostatic assumptions and dynamic pressure treatments are applied to study the helical secondary flows in an experiment curved channel. The agreements of vertically-averaged velocities between the simulated results obtained by using different turbulence models with different pressure solution techniques and the measured data are satisfactory. Their discrepancies with respect to surface elevations, superelevations and secondary flow patterns are discussed.     

STABILITY IN THE CIRCULAR PIPE FLOW OF FIBER SUSPENSIONS

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｆｌｏｗｏｆｆｉｂｅｒｓｕｓｐｅｎｓｉｏｎｓｉｓｖｅｒｙｃｏｍｍｏｎｉｎｍａｎｙｆｉｅｌｄｓｏｆｉｎｄｕｓｔｒｉａｌｐｒｏｄｕｃｔｉｏｎ ,ｓｕｃｈａｓｃｈｅｍｉｃａｌｅｎｇｉｎｅｅｒｉｎｇ,ｍａｔｅｒｉａｌａｎｄｆｏｏｄｐｒｏｃｅｓｓｉｎｇ .Ｉｔｉｓｎｅｃ ｅｓｓａｒｙｔｏｒｅｓｅａｒｃｈｔｈｅｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｆｌｏｗｏｆｆｉｂｅｒｓｕｓｐｅｎｓｉｏｎｓ,ｏｎｅｏｆｗｈｉｃｈｉｓｔｈｅｆｌｏｗｓｔａｂｉｌｉｔｙ .Ｆｉｂｅｒａｄｄｉｔｉｖｅｓｍａｙ…     

NUMERICAL SIMULATION OF DISCONTINUOUS FLOW IN CIRCULAR CONDUITS

ＮＵＭＥＲＩＣＡＬ　ＳＩＭＵＬＡＴＩＯＮ　ＯＦ　ＤＩＳＣＯＮＴＩＮＵＯＵＳ　ＦＬＯＷ　ＩＮ　ＣＩＲＣＵＬＡＲ　ＣＯＮＤＵＩＴＳＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＤＩＳＣＯＮＴＩＮＵＯＵＳＦＬＯＷＩＮＣＩＲＣＵＬＡＲＣＯＮＤＵＩＴＳ￥ＭａｏＺｅ...     

NUMERICAL SIMULATION OF BUBBLE FLOW INTERACTIONS

Bubble flow interaction can be important in many practical engineering applications. For instance, cavitation is a problem of interaction between nuclei and local pressure field variations including turbulent oscillations and large scale pressure variations. Various types of behaviours fundamentally depend on the relative sizes of the nuclei and the length scales of the pressure variations as well as the relative importance of bubble natural periods of oscillation and the characteristic time of the field pressure variations. Similarly, bubbles can significantly affect the performance of lifting devices or propulsors. We present here some fundamental numerical studies of bubble dynamics and deformation, then a practical method using a multi-bubble Surface Averaged Pressure (DF-Multi-SAP©) to simulate cavitation inception and scaling, and connect this with more precise 3-D simulations. This same method is then extended to the study of two-way coupling between a viscous compressible flow and a bubble population in the flow field.     

VISCOUS FLOW BEHAVIOR IN A CURVED ANNULAR DUCT

ＶＩＳＣＯＵＳＦＬＯＷＢＥＨＡＶＩＯＲＩＮＡＣＵＲＶＥＤＡＮＮＵＬＡＲＤＵＣＴ￥ＺｈａｎｇＢｅｎ－ｚｈａｏ（Ｄｅｐｔ．ｏｆＭｅｃｈａｎｉｃｓ，ＺｈｅｊｉａｎｇＵｎｉｖｅｒｓｉｔｙ，Ｈａｎｇｚｈｏｕ３１００２７，Ｐ．Ｒ．Ｃｈｉｎａ）ＦａｎＤａｂ－ｎｉｎ...