FLUID FLOW IN ROTATING HELICAL SQUARE DUCTS

1 .　INTRODUCTIONTherotatinghelicalsquareducthasextensive lyapplicationsinengineeringforenhancingtheratesofheatandmasstransfer ,suchascoolingsystemsforconductorsofelectric generatormo tors ,gasturbines ,separation processes .Becauseoftherotation ,theCoriolisforcecanalsocontrib utetothe generationofsecondaryflow ,whichcomplicatestheflowcharacteristics .To gethighperformanceofthesedevices,itisimportanttofindouttheflowcharacteristicsinrotatinghelicalsquareducts .Duetothecomplexityoftheproble…     

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.     

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.     

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 …     

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

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

THE FLOW IN ROTATING CURVED CIRCULAR PIPE

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

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.     

LAMINAR FLOW AND HEAT TRANSFER IN THE DEVELOPING REGION OF HELICAL SQUARE DUCTS

Simultaneous development of the laminar flow and heat transfer in helical square ducts was numerically studied. The governing equations were written in an orthogonal helical coordinate system and fully parabolized in the axial direction. Results were found out over a wide range of the governing parameters. Two axial velocity entries were taken into account. The development of secondary flow, axial velocity and temperature distribution for the large Dean number were examined in detail and the effects of different governing parameters on the friction factor and the Nusselt number were annlyzee. Many new and interesting conclusions were reached. The present results reveal the nature of fluid flow and heat transfer in the developing region of helical square ducts.     

SEDIMENTATION OF CIRCULAR PARTICLES IN OLDROYD-B FLUID

The sedimentation of circular particles in a vertical channel filled with Oldroyd-B fluid was studied by an improved Distributed Lagrange Multiplier/fictitious domain (DLM) method. The sedimenting behaviors of two particles are presented firstly, which shows that, when the particles are dropped in a viscoealstic fluid, the stable configuration is the one where the particles are aligned parallel to the flow direction when the Mach number M is less than 1 and the elasticity number E is greater than 1. This agrees well with the known experimental in Ref. [1] and simulation results in Ref.[2]. Our simulations also show that, as in Newtonian fluid,the sedimentation of the particles will be accelerated due to the interaction between particles in a viscoealstic fluid.     

THE INFLUENCE OF THE SECONDARY NORMAL STRESS DIFFERENCE OF VISCOELASTIC FLUID ON ECCENTRIC CAPSULE FLOW

ＴＨＥＩＮＦＬＵＥＮＣＥＯＦＴＨＥＳＥＣＯＮＤＡＲＹＮＯＲＭＡＬＳＴＲＥＳＳＤＩＦＦＥＲＥＮＣＥＯＦＶＩＳＣＯＥＬＡＳＴＩＣＦＬＵＩＤＯＮＥＣＣＥＮＴＲＩＣＣＡＰＳＵＬＥＦＬＯＷ￥ＰａｎＤａ－ｌｉｎ（ＧｕａｎｇｄｏｎｇＩｎｓｔｉｔｕｔｅｏｆｏｆＴｅｃ...     

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.     

VISCOUS FLOW BEHAVIOR IN A CURVED ANNULAR DUCT

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

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.     

DIRECT NUMERICAL SIMULATION OF TURBULENT HEAT TRANSFER IN A WALL-NORMAL ROTATING CHANNEL FLOW

1. INTRODUCTIONTurbulent flows with heat transfer in rotatingframe exist in a variety of industrial , geophysicaland astrophysical applications . The rotation in-duces additional body forces ,i .e .,centrifugal andCoriolis forces , acting on the turbulent…     

FINITE ELEMENT ANALYSIS OF THE FLOW INDUCED BY ROTATING BLADES IN AN INCOMPRESSIBLE VISCOUS FLUID

Aerodynamic loads on a multi-bladed helicopter rotor in hovering flight were calculated by solving the three-dimensional incompressible Navier-Stokes equations. The rotor wake effects were accounted by the correction of local geometric angle of attack according to a free-wake modeling in addition to an empirical modification for the tip flow effect. The validity and efficiency of the present method were verified by the comparisons between numerical results and experimental data.     

THEORETIC SOLUTION OF TRANSIENT FLOW OF LIQUID IN THE PIPE WITH FLUID MACHINERY

The transient flow of liquid in the pipe with fluid machinery is analysed in this pa-per.The theoretic solution of the transient flow produced due to the regulation of fluid machin-ery is found by use of the method of the Laplace transformation.     

FINITE ELEMENT ANALYSIS OF VISCOUS FLOW PAST A ROTATING SPHERE

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＶｉｓｃｏｕｓｆｌｏｗｐａｓｔａｂｌｕｆｆｂｏｄｙｈａｓｒｅｃｅｉｖｅｄａｇｒｅａｔｄｅａｌｏｆａｔｔｅｎｔｉｏｎｏｗｉｎｇｔｏｉｔｓｔｈｅｏｒｅｔｉｃａｌａｎｄｐｒａｃｔｉｃａｌｓｉｇｎｉｆｉｃａｎｃｅ .Ｔｈｅｐｒｅｓｅｎｃｅｏｆｖｏｒｔｅｘｓｈｅｄｄｉｎｇ ,ｔｏｇｅｔｈｅｒｗｉｔｈｖｏｒｔｅｘｗａｋｅｓ ,ｉｓｒｅｌａｔｅｄｔｏｔｈｅｐｒｅｓｓｕｒｅｆｌｕｃｔｕａ ｔｉｏｎ ,ｓｔｒｕｃｔｕｒａｌｖｉｂｒａｔｉｏｎ ,ａｎｄｎｏｉｓｅ .Ｔｈｅｂｅｈａｖｉｏｒｏｆｔｈｅｆ…     

FLOW PAST TWO ROTATING CIRCULAR CYLINDERS IN A SIDE-BY-SIDE ARRANGEMENT

Measurements were performed using Particle Image Velocimetry(PIV) to analyze the modification of flow by the combined effects of the rotation and the Reynolds number on the flow past two rotating circular cylinders in a side-by-side-arrangement at a range of 425 ≤ Re≤ 1130,0 ≤α≤ 4(α is the rotational speed) at one gap spacing of T / d =1.11(T and d are the distance between the centers of two cylinders and the cylinder diameter,respectively).A new Immersed-Lattice Boltzmann Method(ILBM) scheme was used to st...     

UNSTEADY FLOW OF POLYMER FLUID BETWEEN COAXIAL CYLINDERS

In the present paper an unsteady flow of polymer fluid,i.e.non-Newtonianfluid is studied.The constitutive equation of upper-convected Maxwell fluid is used.The varia-tional approach due to Kantorovich is used for the unsteady problem of the fluid.A special com-puter program“MACSYMA”is used to get the different approximation of the method of Kan-torovich.The present method developed is called Computational Analytical Method which isavailable for the scientific research.     

THE FLOW PRODUCED IN PARTICLE-SUSPENSION BY AN INFINITE ROTATING DISK:SERIES SOLUTION

To the flow produced in particle-suspension by a rotating disk of infinite extent,the asymptotic behavior at infinity is analyzed.A corresponding series solution is presented.It isshown that this approach yields widely valid solutions of high accuracy for all the cases in whichthat suction or weak injection at the disk surface exists.For the cases that strong injection or par-ticle-free band exists,the series method fails.