FLOW CHARACTERISTICS OF TURBULENT JETS INJECTED OBLIQUELY IN CROSSFLOW

1 .　INTRODUCTIONThejetinacrossflowisahighlycomplexturbu lentflow ,andwithapplicationsinvariousengineeringfields .Theinjectionofajetintothecrossflowcanaltertheflowfieldandresultinaverycomplexthree di mensionalflowstructure .Numericalsimulationisanimportantmethodtostudythetransversejet cross flow .Chang[1] ,Tamamidis[2 ] ,Lakehal[3] etc .,usedthenormalk εmodelandwallfunctionmethodtosim ulatetheflowfieldoftheturbulentjet .Althoughthenormalk εmodelgivespredictionsofengineeringaccu racyint…     

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.     

ANALYSIS OF TWO-PHASE FLOW PRESSURE BUILDUP DATA FROM WELL IN AN INFINITE MULTIWELL RESERVOIR

A general method has been developed for analyzing two-phase flow pressure buildup data from a well located in a system of both production and injection wells completed in an infinite muhiwell reservoir. The analysis technique assumes that the tested well has established its own drainage area before shut-in and a linear reservoir pressure trend dominates the well pressure behavior at the instant of shut-in. And for the two-phase flow problems the horizontal saturation gradients are assumed to be negligible. The entire pressure rcsponse, whether or not conventional semilog straight lines exist, can be analyzed and the Injection-Production Ratio （IPR）, the total fluid （oil/water） mobility, the average drainage-area pressure, and also the skin factor can be calculated much easily. The validity and applicability of the method are demonstrated by a field example. The technique by using the type curves for analyzing the pressure-buildup data is also presented here.     

NUMERICAL SIMULATION OF FLOW FIELDS IN A NATURAL DRAFT WET-COOLING TOWER

The flow field in the hyperbolic natural draft wet-cooling tower, which has great effects on the economy and security of power plant, was studied through numerical simulation. The mathematical model was established and analyzed in order to optimize the cooling-tower and to evaluate its efficiency. Various working conditions were considered and compared with each other, such as the circulating water flux, air temperature and tower resistance. It is concluded that when the cooling-tower runs without wind, there is a vacuum region inside the tower and the pressure rises with the increase of the tower height. Meanwhile, the inner flow field is axisymmetrical. The air velocity achieves its climax at the axis. It is also found that the effect of circulating water temperature is equivalent to that of the water flux.     

THREE-DIMENSIONAL TURBULENCE NUMERICAL SIMULATION OF A STEPPED SPILLWAY OVERFLOW

In this paper, the κ-ε two-equation turbulence model was used to simulate the three-dimensional turbulent flow of the stepped spillway at the Yubeishan reservoir. In order to solve the curved free water surface and to handle the complex boundary conditions, the fractional Volume Of Fluid (VOF) model that is applicable to the solution of the stratified two-phase flow was intorduced to the κ-ε turbulence model and the unstructured grid was used for the discretization of the irregular simulation domain. By these methods, the turbulent flow field of the stepped spillway was simulated successfully.The location of the free surface along the spillway, the magnitude and distribution of the velocity, the pressure distribution on the step surface, the turbulence kinetic energy and turbulence dissipation rate were obtained by simulation. The changes and distributions of these characteristics along the width of the spillway were also obtained. The energy dissipation ratio of the stepped spillway was calculated according to the upstream and downstream water depth and velocities.     

NUMERICAL INVESTIGATION OF TURBULENT COUNTER-GRADIENT-TRANSPORT IN ASYMMETRIC FLOW WITH A JET

By using the Reynolds Stress Closure Model (RSM), turbulent Counter-Gradient-Transport (CGT) phenomenon was numerically investigated in asymmetric flow with a jet, and the computational results were compared with experimental data. The computational results show that the negative turbulent energy production only appears at some certain stations in CGT region, this fact indicates that the CGT phenomenon exists more widely than the negative turbulent energy production; while the CGT region exists all along, it gradually shrinks in the favorable pressure gradient zone until the position of the wing central part is reached, where it vanishes, but it appears in the adverse pressure gradient region in addition, the location in the flow where uυ = 0 switched sides, relative to where aU/au = 0, from favorable pressure gradient to adverse pressure gradient. The pressure gradient takes an important effect on the region of negative turbulent energy production and CGT.     

DISPERSION OF CYLINDRICAL PARTICLES IN TURBULENT FLOWS

With consideration of the Stokes drag and virtual mass force, the equations for mean and fluctuating velocities in rotation and translation were given for rigid cylindrical particles moving in a turbulent flow. Then the rotational and translational dispersion coefficients of particle were derived.The relationships between the dispersion coefficients and flow length scale as well as particle characteristic parameters were analyzed. The resulting dispersion coefficients were proved to decrease as the particle length increases. The conclusions are helpful for the further research on the motion of cylindrical particles in turbulent flows.     

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 PHYSICAL MODEL FOR PREDICTING THE PRESSURE DROP OF GAS-LIQUID SLUG FLOW IN HORIZONTAL PIPES

A comprehensive treatment of all sources of pressure drop within intermittent gas-liquid flow is presented. A slug unit is divided into three parts and the pressure gradient of each part is calculated separately. In the mixing zone the momentum theory is employed and the mixing process between the film and slug is simulated by a two-dimensional wall jet entering a large reservoir to calculate the mixing length. The boundary layer theory is utilized to calculate the pressure drop for the slug body and the momentum equation of the film zone is integrated to calculate the pressure drop for the film zone. The pressure drop predicted in present model is in good agreement with all the measurements.     

SIMULTANEOUS PIV／PTV MEASUREMENTS OF BUBBLE AND PARTICLE PHASES IN GAS-LIQUID TWO-PHASE FLOW BASED ON IMAGE SEPARATION AND RECONSTRUCTION

1 .　INTRODUCTIONMultiphaseflowisacomplicatedsystemofthesimultaneousflowofgas ,liquidand/orsolidphas esinvariouscombinations .Theinteractionofthedispersed phasewiththecontinuousphasehasagreateffectontransferprocessesofheat ,massandmomentumbetweenthe phases .Therelativeve locitiesbetweenthetwo phases ,theinterfacialareaandtheshapeofthedispersedphasearethekeydependent parametersintransfer processes.Therefore ,simultaneousmeasurementofthedy namicmotionofeachphaseinmultiphaseflowisveryimporta…     

EFFECT OF SURFACTANT ON TWO-PHASE FLOW PATTERNS OF WATER-GAS IN CAPILLARY TUBES

Flow patterns of liquid-gas two-phase flow were experimentally investigated. The experiments were carried out in both vertical and horizontal capillary tubes having inner diameters of 1.60 mm. The working liquid was the mixture of water and Sodium Dodecyl Benzoyl Sulfate (SDBS). The working gas was Nitrogen. For the water/SDBS mixture-gas flow in the vertical capillary tube, flow-pattern transitions occurred at lower flow velocities than those for the water-gas flow in the same tube. For the water/SDBS mixture-gas flow in the horizontal capillary tube, surface tension had little effect on the bubbly-intermittent transition and had only slight effect on the plug-slug and slug-annular transitions. However, surface tension had significant effect on the wavy stratified flow regime. The wavy stratified flow regime of water/SDBS mixture-gas flow expanded compared with that of water-gas.     

SOLUTION OF RELATIVE PERMEABILITY OF TWO-PHASE FLOW IN POROUS MEDIUM

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FLOW PATTERN AND PRESSURE LOSS OF OIL-WATER TWO-PHASE FLOW IN HORIZONTAL STEEL PIPE

Experimental Study on oil-water two-phase flow patterns and pressure loss was conducted on a horizontal steel pipe loop with 26. 1mm inner diameter and 30m total length. The working fluids are white oil, diesel oil and tap water. Several instruments, including a new type of liquidprobe are successfully integrated to identify 7 different flow patterns. The characteristics of the flow patterns and the transition process were observed and depicted in this paper.Investigation revealed that the pressure loss was mainly depended on the flow paiterns.     

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.     

A METHOD FOR MEASUREMENT OF GAS CONTENT IN SLURRY PIPELINE

1. INTRODUCTIONMost commercial slurries in hydrotransportpipelines contain some free entrained gas . Highspeed photographs inside the centrifugal pump in-dicate that the air phase separated onthe outer sideof the i mpeller forms of mist ,entrained or emulsi-fied,and that the gas phase may accumulate andjamthe flow channel inside the pump[1]. The ex-peri mental results indicated that the pump flow-rate ,head and efficiency decrease ,the pump loo-sing momentum abruptly ,shaking fairly violen…     

ADDITIONAL PRESSURE LOSSES OF SOLID-LIQUID FLOW IN AN OSCILLATING PIPELINE

1. INTRODUCTIONThere are abundant resources in immense oceans. Manganese nodule on the deep sea bed is a kind of mineral resources, the size of which ranges from 5mm to 200mm in diameter (David 1974). In the last decades, several mining systems have been …     

THE FLOW CONTROL IN PIPELINE SYSTEM

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STUDY OF THE ATOMIZED FLOW IN HYDRAULIC ENGINEERING

l.mThODUCnONInhydraulicengineeringifwaterdischargesfromtheflipbucketatcertainhighspeed,atomizedflowwouldformowingtothespreadingoftheaeratedjetandthesplashingasthisaeratedjetimpingeswiththewaterdownstream.Thisatomizedflowmaythreatenthesafe-tyofthehydraulicengineering,sometimesevencausescertainharm,sincethisflowmightproduceheavyrainaswellasheavyfoginacertainareadownstreamofthedamundertheinfluenceofupstreamwindanddownstreamtopography.Insomehydraulicprojectsonceflooddischargesthereexistsarelativ…     

THE FRICTIONAL RESISTANCE CHARACTERISTICS OF GAS LIQUID TWO PHASE FLOW IN HELICAL COILED TUBES

1.　INTRODUCTIONThe equipments with helical-coiled tubes have been widely applied in industry,such asnylon production,boiler,special heat exchangers,nuclear power station and so on.Manyauthors have been done lots of experimental studies on frictional resistance characteristics ofgas liquid two-phase flow in helical-coiled tubes[1 ] [2 ] .But,there has been rate related treat-mentby means of dimension analysis andπtheorem.The experimentof frictional resistance characteristics of gas-liqui…