ON THE MECHANISM OF DRAG REDUCTION IN HIGH CONCENTRATION NON-HOMOGENEOUS PIPE FLOW

In this paper a method for calculating the resistance force in high concentrationnon-homogeneous pipe flow is suggested.Comparing with experiment,it is shown that the theo-retical results are in good agreement with the experimental ones.     

TRANSPORT EFFICIENCY OF THE SPIRAL FLOW IN CIRCULAR PIPE

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＧｒａｉｎｍａｔｅｒｉａｌｔｒａｎｓｐｏｒｔｉｎｐｉｐｅｆｌｏｗｈａｓａｈｉｓｔｏｒｙｏｆｍｏｒｅｔｈａｎｏｎｅｈｕｎｄｒｅｄｙｅａｒｓ .Ｉｎｒｅｃｅｎｔｓｅｖｅｒａｌｄｅｃａｄｅｓｔｈｅｔｅｃｈｎｏｌｏｇｙｈａｓｂｅｅｎｄｅｖｅｌｏｐｉｎｇｖｅｒｙｒａｐｉｄ ｌｙ .Ｔｈｅｒｅａｒｅｍｏｒｅｔｈａｎ 2 6ｓｏｒｔｓｏｆｍａｔｅｒｉａｌｓｓｕｃｈａｓｃｏａｌ,ｓａｎｄ ,ｃｏｎｃｅｎｔｒａｔｅ ,ｔａｉｌｉｎｇｓａｎｄｏｔｈｅｒｇｒａｉｎｍａｔｅ ｒｉａｌｓａｒｅｔｒａｎｓｐｏ…     

THE FLOW IN ROTATING CURVED CIRCULAR PIPE

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

LAMINAR FLUID FLOW IN HELICAL ELLIPTICAL PIPE

1.　INTRODUCTIONHelicalductsappearinvariousindustrialapplictionsandadetailedknowledgeofthefluidflowbehaviorisimportantforpredictingthepressuredropandheatandmasstransfercharacteristics.Experimentalandtheoreticalanalysishaveattestedthatthesecondaryflowappearsthenormalcross-sectionbecauseofthecurvature.Thissecondaryflowisveryfaintcomparedwiththeaxialflow,butitcausestheincreaseofheattransfer.Thestudyonthisflowbeganin1927withthepaperofDean[1],inwhichtheflowintoroidalsystemwasstudied.Sincethen…     

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.     

STABILITY IN THE CIRCULAR PIPE FLOW OF FIBER SUSPENSIONS

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

BASIC HYDRODYNAMICS CHARACTERISTICS OF CAVITY SPIRAL FLOW IN A LARGE SIZE LEVEL PIPE

Based on the observation of a model test and in combination with some theoretical analysis, the researches of some basic hydrodynamics characteristics of cavity spiral flow in a large size level pipe with a shaft-inlet is presented in the paper, which include the basic flow pattern, formation condition of the cavity spiral flow, discharge Q, cavity diameter d0, wall pressure coefficient Cpw, velocity distribution, total energy dissipation rate η etc. The results show that the basic flow patterns can be divided into three zones according to the variations in amount of ventilation Ф, cavity diameter d0 and gas pressure p0 within cavity spiral flow when the upstream and downstream water level changes and that the basic hydrodynamics characteristics change with the flow pattern and have the different behaviour.     

A NEW APPROACH TO THE SIMULATION OF UNSTEADY SUBCRITICAL FLOW

ＡＮＥＷＡＰＰＲＯＡＣＨＴＯＴＨＥＳＩＭＵＬＡＴＩＯＮＯＦＵＮＳＴＥＡＤＹＳＵＢＣＲＩＴＩＣＡＬＦＬＯＷ￥ＭａｏＺｅ－ｙｕ（ＤｅｐａｒｔｍｅｎｔｏｆＨｙｄｒａｕｌｉｃＥｎｇｉｎｅｅｒｉｎｇ，ＴｓｉｎｇｈｕａＵｎｉｖｅｒｓｉｔｙＢｅｉｊｉｎｇ１０００８...     

ACCURATE PIPE TOP-ENTRY JUNCTION MODEL FOR STEADY AND UNSTEADY FLOWS

ＡＣＣＵＲＡＴＥ　ＰＩＰＥ　ＴＯＰ－ＥＮＴＲＹ　ＪＵＮＣＴＩＯＮ　ＭＯＤＥＬ　ＦＯＲ　ＳＴＥＡＤＹ　ＡＮＤ　ＵＮＳＴＥＡＤＹ　ＦＬＯＷＳＡＣＣＵＲＡＴＥＰＩＰＥＴＯＰ－ＥＮＴＲＹＪＵＮＣＴＩＯＮＭＯＤＥＬＦＯＲＳＴＥＡＤＹＡＮＤＵＮＳＴＥＡＤＹＦＬＯ...     

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.     

STEADY ENTRANCE FLOW IN A STRAIGHT CIRCULAR PIPE WITH SLOWLY VARYING CROSS SECTION

1.INTRODUCTIONItiswellknownthatmanyvasculardiseasesarecloselyrelatedtothebloodflowinves-sels[1-3j.Thebloodflowthroughthearterieswithvaryingcrosssectionhasheldthein-terestsofmanyinvestigatorsforalongtimeL4-6j.Inthepreviousstudies,thebloodf1owinarterieswas,however,assumedtobefullydeveloped.Sincestenosesfrequentlydevelopatsitesneartheoriginofbranches[2-3j,whichareintheentranceregion,itisimportanttostudytheentranceflowinaconverging-divergingpipe,whichisamodelofentrancestenosis-Manyinvestigat…     

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.     

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.     

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.     

DEBRIS FLOW KINETIC CHARACTERISTICS UNDER NATURAL CONDITIONS

The study for debris flow kinetic characteristics can not be approached byexperiments due to their complexity and distransparency,etc.This paper is a picture of debrisflow kinetic characteristics based on the natural debris flow observation and experiments.Thekinetic characteristics of viscous debris flow are obtained by radar veloeimeter and ultrasoniclevel meter in jiangjia ravine.From those,the following are suggested:in natural channel,debris flow can be classified as three kinds of type:strong turbulent debris flow;turbulent debrisflow;weak turbulent debris flow:meanwhile the Reynolds number(Re)is chosen as an indexfor the classification.     

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…     

THE METHOD OF SEMI-FALSE TRANSIENT FOR COMPUTING THE FLOW INTO POROUS MEDIUM IN THE CIRCULAR PIPE

The method of semi-false transient was used to numerically compute the incompressible steady flow into the porous medium n this paper. The fundamental equations were established and numerically solved in the united flow field,which included the space region and the porous region. The non-equidistant non-orthogonal semi-staggered mesh system was used in the method of semi-false transient.The computational results of two problems concerning the flow into porous medium from space region,in which there was the backward flow besides main flow, were obtained adn discussed. It is seen from the results that the backward flow is generally not present in the porous medium as the osmotic resistance is very large.     

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

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＡｘｉｓｙｍｍｅｔｒｉｃｆｕｌｌｙｄｅｖｅｌｏｐｅｄｔｕｒｂｕｌｅｎｃｅｉｎｐｉｐｅｆｌｏｗｐｒｏｖｉｄｅｓｏｎｅｏｆｔｈｅｓｉｍｐｌｅｓｔａｎｄｍｏｓｔｒｅ ｐｒｏｄｕｃｉｂｌｅｌａｂｏｒａｔｏｒｙｆｌｏｗｓｆｏｒｅｘｐｅｒｉｍｅｎｔａｌｗａｌｌｔｕｒｂｕｌｅｎｃｅｓｔｕｄｉｅｓ,ａｎｄｏｗｉｎｇｔｏｉｔｓｃａｌｃｕｌａｔｉｏｎｐｏｓｓｉｂｉｔｉｅｓ,ｉｓｏｆｇｒｅａｔｉｎｔｅｒｅｓｔｔｏｒｅｓｅａｒｃｈｅｒｓ .Ｉｎｔｈｅｍｏｒｅｔｈａｎｈａｌｆａｃｅｎｔｕｒｙｓｉｎ…     

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

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

SIMULATION OF OIL-WATER TWO PHASE FLOW AND SEPARATION BEHAVIORS IN COMBINED T JUNCTIONS

The combined T junctions used for the oil-water separation have the advantages of compactness in structure,consistency in effects and economy in cost.The mixture turbulence model and the Eulerian multi-fluid model are used to simulate the flow and phase distribution in the combined T junctions.The effects of structural parameters such as the branched pipe interval and height on the flow distribution and the separation behaviors are studied.The results show that the combined T junctions under fixed inlet and outlet boundary conditions form a single hydraulic equilibrium system in which the fluid energy distributes freely till a balance is achieved.The split-flow promotes the separation of the immiscible oil and the water.The separation efficiency increases with the increase of the branched pipe interval and changes slightly with the increase of the branched pipe height.The structural change of the combined T junctions may change the flow direction in the branched pipes.Simulation results can provide some guidance for the design of the combined T junctions as one kind of oil-water separator.