3D FLOW INSIDE BUBBLE-TYPE VORTEX BREAKDOWN: AN EXPERIMENTAL INVESTIGATION VIA LDV

1 .　INTRODUCTIONRichvortex phenomenahavebeenfoundinrotatingflows ,suchassecondaryflowandvortexbreakdown .Alargequantityofexperimentalandnumericalinvestigationshasbeendonetogainin sightintovortexdynamicsandtheir generationmechanism .However ,physicsforunderstandingthevortexdynamicsespeciallyvortexbreakdownisstilllimitedtoagreatextent.Toclarifyitsstruc tureanddynamics ,verysmallexternaldisturbanceandveryfinegridarrangementarenecessaryforexperimentalmeasurement.Thenvaliddatawithalloweduncer…     

3-D MEASUREMENT OF VORTEX BREAKDOWN IN CLOSED CYLINDRICAL CONTAINER VIA LDV

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＶｏｒｔｅｘｂｒｅａｋｄｏｗｎｐｈｅｎｏｍｅｎｏｎｈａｓｂｅｅｎｉｎｖｅｓｔｉ ｇａｔｅｄｉｎｖａｒｉｏｕｓｓｗｉｒｌｉｎｇｆｌｏｗｓ,ｆｏｒｉｎｓｔａｎｃｅｅｘｔｅｒｎａｌｆｌｏｗｓａｒｏｕｎｄｄｅｌｔａｗｉｎｇ ,ａｔｔｈｅｏｕｔｌｅｔｏｆｔｕｒｂｏｍａｃｈｉｎ ｅｒｙ ,ａｓｗｅｌｌａｓｉｎｔｅｒｎａｌｆｌｏｗｓｉｎｆｕｒｎａｃｅａｎｄｃｏｍｂｕｓｉｏｎｃｈａｍｂｅｓ.Ｔｈｅｖｏｒｔｅｘｂｒｅａｋｄｏｗｎｉｓａｔｅｒｍａｓｓｏｃｉａｔｅｄｗｉｔｈａｎａｂｒｕｐｔｃｈａ…     

EXPERIMENTAL INVESTIGATION ON VORTEX BREAKDOWN IN SPIN-UP AND SPIN-DOWN PROCESSES VIA PIV

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＲｏｔａｔｉｎｇｆｌｏｗｓｉｎｃｙｌｉｎｄｒｉｃａｌｃｏｎｔａｉｎｅｒｓｔｈａｔａｒｅｉｎｄｕｃｅｄｂｙｒｏｔａｔｉｎｇｂｏｕｎｄａｒｉｅｓａｒｅｏｆｇｒｅａｔｉｍｐｏｒ ｔａｎｃｅｔｏｔｈｅｄｅｓｉｇｎｅｒｓｏｆｆｌｕｉｄｍｉｘｉｎｇｄｅｖｉｃｅｓ.Ｗｉｔｈｓｉｍｐｌｅｇｅｏｍｅｔｒｙａｎｄｂｏｕｎｄａｒｉｅｓ,ｓｕｃｈｔｙｐｅｏｆｆｌｏｗｓａｒｅｓｔｉｌｌｏｆｍｕｃｈｐｒａｃｔｉｃａｌｓｉｇｎｉｆｉｃａｎｃｅ .Ｔｈｅｒｅａｒｅｎｕ ｍｅｒｏｕｓｐｒｏｂｌｅｍｓｉｎｆ…     

JOINT INVESTIGATION OF ROTATING FLOW WITH VORTEX BREAKDOWN USING CFD, VISUALIZATION AND LDV

Vortex breakdown of the steady axisymmetic rotating flow in a confined cylindrical container with a rotating endwall was numerically and experimentally studied. High-quality precision-controlled turntable facilities were established at Shanghai Jiaotong University and Tokyo Denki University independently. Collaborative investigations of vortex breakdown were carried out using CFD, Laser Doppler Velocimetry （LDV） and streakline visualization, respectively. The characteristics of vortex breakdown were delineated in terms of comparative investigation using numerical and experimental results. SIMPLEC scheme and FMG multigrid was applied to numerical simulation. Numerical simulation was extensively compared with streakline visualization and LDV measurements, showing qualitative and quantitative agreements.     

NUMERICAL STUDY ON THE VORTEX STRUCTURES IN THE WAKE OF AN OSCILLATING CIRCULAR CYLINDER IN A UNIFORM FLOW

ＮＵＭＥＲＩＣＡＬＳＴＵＤＹＯＮＴＨＥＶＯＲＴＥＸＳＴＲＵＣＴＵＲＥＳＩＮＴＨＥＷＡＫＥＯＦＡＮＯＳＣＩＬＬＡＴＩＮＧＣＩＲＣＵＬＡＲＣＹＬＩＮＤＥＲＩＮＡＵＮＩＦＯＲＭＦＬＯＷＬｕＸｉ－ｙｕｎ；ＴｏｎｇＢｉｎｇ－ｇａｎｇ；ＺｈｕａｎｇＬｉ－ｘｉａｎ...     

NUMERICAL PREDICTION OF VORTEX FLOW IN HYDRAULIC TURBINE DRAFT TUBE FOR LES

The three-dimensional unsteady turbulent flow is studied numerically in the whole flow passage of hydraulic turbine, and vortex flow in the draft tube is predicted accurately in this paper. The numerical prediction is based on the Navier-Stokes equations and Large-Eddy Simulation （LES） model. The SIMPLE algorithm with the body fitted coordinate and tetrahedroid grid system is applied for the solution of the discretization governing equations.     

STABILITY IN THE CIRCULAR PIPE FLOW OF FIBER SUSPENSIONS

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

STABILITY OF VORTEX STREET IN GAS-LIQUID TWO-PHASE FLOW

The stability of the Karmen vortex street in gas-liquid two-phase flow was studied experimentally and theoretically. The values of the parameter h/l characterizing the vortex street structure (i. e. , the ratio of the vortex street width to the distance between two vortexes) for a stable vortex street in gas-liquid two-phase flow were obtained for the first time. The parameter h/l was prpved to be a variable, not a constant as in single-phase flow, h/l is related to the upstream fluid void fraction. In gas-liquid two-phase fluid flow to form a steady vortex street is more difficult than in a single-phase fluid flow. Because in the unsteady vortex shedding the vortex shedding band frequency is broader than the one in the single phase fluid flow, so it is easier to induce the cross-cylinder resonance than in the single phase fluid flow, and this case should give rise to the attention of engineers.     

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.     

RESEARCH ON THE FLOW PROPERTY IN THREE DIMENSIONAL CAVITY OF MICRO-CHANNEL

1. INTRODUCTIONOver the past decade , many attentions havebeen paid to the liquid flowin microchannels dueto the development in microfluidic devices and sys-tems .The separation and mixing of the fluidin mi-crochannels have special characteristics[1]. The re-search of liquid-liquid extraction technique basedon the microfluidic chip is an i mportant aspect inthe field of microfluidic chip analysis . Comparedwith the traditional liquid-liquid extraction tech-nique , the micromation of extra…     

RESEARCH ON TURBULENT FLOW WITHIN THE VORTEX PUMP

Based on the standard κ-ε turbulence model and the RANS equations, the finite volume method and the SIMPLE algorithm were adopted to carry out the three-dimensional viscous numerical simulation of the internal flow within a vortex pump in double reference frames. According to the resuits of numerical simulation, the internal flow in the vortex pump was analyzed, and the calculated results of blade surface pressure of the impeller were compared with experimental resuits. The maximum relative error is 6. 6% between calculated value and experimental value of the pump head under operation conditions.     

NUMERICAL SIMULATION OF THE TURBULENT FLOW IN ROTATING DUCT

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

STUDY OF VORTEX CHARACTERISTICS OF THE FLOW AROUND A HORIZONTAL CIRCULAR CYLINDER AT VARIOUS GAP-RATIOS IN THE CROSS-FLOW

1. INTRODUCTION The flow around a horizontal circular cylinder near a plane boundary (fixed wall) is of great significance in Hydrodynamics. For instance, sewagepipelines in water body of rivers in environmental engineering, conveying pipelines and optica…     

EXPERIMENTAL AND NUMERICAL INVESTIGATION OF FREE SURFACE VORTEX

An experimental model was set up to investigate the formation and evolution of the free surface vortex. A Particle Image Velocimetry （PIV） was used to measure the free surface vortex flow field at different development stages. Flow visualization was used to locate the vortex position and find its structure. Empirical formulas about the critical submergence and the whole field structure were obtained. It is found that the tangential velocity distribution is similar to that of the Rankine vortex and the radial velocity changes little in the vortex functional scope. Vortex starts from the free surface and gradually intensifies to air entrainment vortex. The vortex core moves during the formation and evolution of the free surface vortex. Based on the experimental model, the vortex position and structure were predicted by numerical simulation combined with a vortex model and compared with that of the experiments, which shows satisfactory agreement.     

FORMATION AND INFLUENCING FACTORS OF FREE SURFACE VORTEX IN A BARREL WITH A CENTRAL ORIFICE AT BOTTOM

Based on the Navier-Stokes equations with considering the effect of the Coriolis force, the finite volume method was employed to discretize the governing equations, the SIMPLE method was adopted to solve the discretized equations, and the flow field in a barrel with an outlet at the center of the bottom was simulated. The numerical results agree well with the experimental data. From the Lagrangian, the relations among the acceleration, the Coriolis force and the viscosity force were analyzed. The results show that the Coriolis force is the major factor that causes the formation of the vortex. The flow fields in the flume under different incoming flow conditions were numerically simulated using the software Fluent. The numerical simulations show good agreement with the experiments for the shape and position of the vortex.     

NUMERICAL SIMULATION OF THE EFFECT OF FILLET FORMS ON APPENDAGE－BODY JUNCTION FLOW

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＴＨＥＥＦＦＥＣＴＯＦＦＩＬＬＥＴＦＯＲＭＳＯＮＡＰＰＥＮＤＡＧＥ－ＢＯＤＹＪＵＮＣＴＩＯＮＦＬＯＷＬｉＤｉｎｇ；ＺｈｏｕＬｉａｎ－ｄｉ（ＣｈｉｎａＳｈｉｐＳｃｉｅｎｔｉｆｉｃＲｅｓｅａｒｃｈＣｅｎｔｅｒＰ．...     

PROPULSIVE PERFORMANCE AND VORTEX SHEDDING OF A FOIL IN FLAPPING MOTION

1 .　INTRODUCTIONInsectsandfishhaveexperiencedabillions yearprocessofevolutionwithnaturalselectionfortheirsurvivalandhavedevelopedtheirsuperiorandcomplete performanceofflightandswim ming .Usually ,aflappingmotionisabasicmodeoflocomotionforinsects ,birds ,andfish .Thrustandliftaregeneratedwhentheflappingwingsortailsinteractwiththesurroundingfluids .Becauseofthehighlyunsteadynatureofviscousflowaroundaflappingwing ,itisfarfromsatisfactorytounderstandthephysicalmechanismandvortexsheddinginuns…     

THE BUBMAC METHOD-A NUMERICAL METHOD BUBBLE DYNAMICS IN VORTEX CORE

This paper presents a numerical method called BUBMAC method,whichis based on the Marker And Cell(MAC) technique,to numerically simulate the problemof bubble dynamics in vortex core. With the incorporation of the azimuthal velocity intothe momentum equation, the model takes into account the complete interaction betweenthe bubble dynamics and the vortex flow field.The three momentum equations (N-Seqs.) are solved numerically by the finite-difference methed, and the motion of bubblesurface is described by tracing massless marker particles distributed only on the surface ofthe bubble. With some important medifications to the original MAC method, the numeri-cal accuracy of the method is conisderably increased. The validation of the proposed BUB-MAC method is checked by comparing the numerical results with some available analyticalsolutions in the cases of spherical bubble evolution and with numerical results in the casesof nonspherical collapse of bubble and bubble evolution in tip-vortex core. The compar-iso     

A NUMERICAL MODEL OF THE WEIS-FOGH MECHANISM WITH A SEPARATION VORTEX

ＡＮＵＭＥＲＩＣＡＬＭＯＤＥＬＯＦＴＨＥＷＥＩＳ－ＦＯＧＨＭＥＣＨＡＮＩＳＭＷＩＴＨＡＳＥＰＡＲＡＴＩＯＮＶＯＲＴＥＸＺｈａｎｇＳｈｅ－ｓｈｅｎｇ；ＷａｎｇＸｉａｎ－ｆｕ（ＷｕｈａｎＴｒａｎｓｐｏｒｔａｔｉｏｎＵｎｉｖｅｒｓｉｔｙ，Ｗｕｈａｎ４３００...     

SIMULATION OF LOW-CONCENTRATION SEDIMENT-LADEN FLOW BASED ON TWO-PHASE FLOW THEORY

Low concentration sediment-laden flow is usually involved in water conservancy, environmental protection, navigation and so on. In this article, a mathematical model for low-concentration sediment-laden flow was suggested based on the two-phase flow theory, and a solving scheme for the mathematical model in curvilinear grids was worked out. The observed data in the Zhang River in China was used for the verification of the model, and the calculated results of the water level, velocity and river bed deformation are in agreement with the observed ones.