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.     

LIQUID-GAS TWO PHASE FLOW RATES METERING BY DUAL PRESSURE DIFFERENTIAL MEASUREMENTS

The measurement of the overall mass flow rates in a two phase, gas/liquid pipeline is considered on the basis of dual pressure differential measurements for a combined contraction/frictional pipe type of flow meter and a numerical model to predict overall mass flow rates from pressure differentials measured from this type of flow meter is presented. The experiments generally conform with the predictions of the flow rates prediction model. Whilst the practicability of such metering of two phase flows is clearly demonstrated, application of the method would require careful calibration to allow for the influence of nozzle coefficients, pipe Reynolds number and void fraction upon the one dimensional compressible flow equations through wall friction factor and interphase slip effects.     

NUMERICAL SIMULATION OF GAS-WATER LEAKAGE FLOW IN A TWO LAYERED COALBED SYSTEM

For a two layered coalbed system in possession of the slightly permeable interlayer, a mathematical model was established to describe the methane and water flows between coal seams and the internal migration and the distribution of fluids in a slightly permeable interlayer. Meanwhile, this model has included the potential effect of matrix shrinkage associated with desorption on the coal permeability. The numerical results were obtained by the finite difference method, and then the production forecasts for the two layered coalbed system were conducted in combination with the geological data of a certain area in the Qinshui Basin. Through analyzing the internal migration and distribution of fluids in the slightly permeable interlayer and its effect on the coalbed methane well production, the results indicate that the prediction of the gas production rate and the cumulative gas production will be higher if the permeability of the interlayer is neglected. Furthermore, it is also found that the matrix shrinkage could produce an effect on the coal permeability, thus affecting the production performance.     

HYDRAULIC PERFORMANCES OF SKIMMING FLOW OVER STEPPED SPILLWAY

Hydraulic performances of skimming flow over stepped spillway was studied by means of hydraulic model experiment. The stepped spillway is a modification of the WES (Waterways Experiment Station) standard spillway. The main objective of the experiment was to study the performances of skimming flow over stepped spillway, which include the skimming flow regime, the flow depth on the spillway , the effect of air en-trainment and the energy dissipation. Presented in this paper, the experimental results indicated that the stepped spillway is more effective at dissipating energy, the dissipation ratio decreases with increasing discharge, and the free surface air entrainment on stepped spillway occurs much more upstream than on smooth spillway.     

NUMERICAL MODELLING OF THE WATER AIR TWO PHASE JET INTO A PLUNGE POOL

１．　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｆｌｏｗｆｉｅｌｄａｎｄｅｎｅｒｇｙｄｉｓｓｉｐａｔｉｏｎｉｎｐｌｕｎｇｅｐｏｏｌａｒｅｏｆｐｒａｃｔｉｃａｌｉｍｐｏｒｔａｎｃｅｆｏｒｄａｍｅｎｇｉｎｅｅｒｉｎｇ．Ｔｈｅａｒｅａｔｉｏｎｈａｓｉｍｐｏｒｔａｎｔｅｆｆｅｃｔｓｏｎｔｈｅｆｌｏｗｉｎｐｌｕｎｇｅｐｏｏｌ［１］　．Ｉｎｔｈｅｃｏｎｖｅｎｔｉｏｎａｌｍａｔｈｅｍａｔｉｃａｌｍｏｄｅｌｓｏｆｗａｔｅｒｆｌｏｗｉｎｈｙｄｒａｕｌｉｃｅｎｇｉｎｅｅｒｉｎｇ，ｔｈｅａｒｅ…     

NUMERICAL CALCULATION OF THREE-DIMENSIONAL TURBULENT FLOW IN A DISTORTING DUCT

A Navier-Stokes procedure based on the Finite Volume Method (FVM) is developed to calculate three-dimensional duct flows with complex geometry. This method is applied to analyze the flow in a distorting duct, and the numercal results are in good a-greement with the experimental ones.     

A FINITE ELEMENT AND BOUNDARY ELEMENT METHOD OF NUMERICAL SIMULATION OF TWO DIMENSIONAL AND TWO PHASE FLOW

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A NON LINEAR ANALYSIS OF TWO PHASE FLOW INSTA BILITY IN PARALLEL CHANNELS OF A BOILING SYSTEM

１．　ＩＮＴＲＯＤＵＣＴＩＯＮＴｗｏｐｈａｓｅｆｌｏｗｉｎｓｔａｂｉｌｉｔｙａｒｅｏｆｔｅｎｅｎｃｏｕｎｔｅｒｅｄｉｎａｗｉｄｅｒａｎｇｅｏｆｅｎｇｉｎｅｅｒｉｎｇｓｙｓｔｅｍｓ，ｓｕｃｈａｓｎｕｃｌｅａｒｒｅａｃｔｏｒｓ，ｓｔｅａｍｐｏｗｅｒｐｌａｎｔｓ，ｓｐｅｃｉａｌｈｅａｔｅｘｃｈａｎｇｅｒｓ，ｓｔｅａｍｇｅｎｅｒａｔｏｒｓ，ｃｈｅｍｉｃａｌｉｎｄｕｓｔｒｙｅｑｕｉｐｍｅｎｔｓａｎｄｓｏｏｎ［１］［２］　．Ｉｎｔｈｅｓｅｓｙｓｔｅｍｓ，ｔｗｏｐｈａｓｅｆｌｏｗｉｎｓｔａｂｉｌｉｔ…     

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.     

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 THROUGH THROAT-TYPE ENERGY-DISSIPATORS

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｏｃｏｎｖｅｒｔａｄｉｖｅｒｓｉｏｎｔｕｎｎｅｌｉｎｔｏａｆｌｏｏｄｄｉｓ ｃｈａｒｇｅｔｕｎｎｅｌｃａｎｓａｖｅａｌａｒｇｅａｍｏｕｎｔｏｆｉｎｖｅｓｔｍｅｎｔ.Ｔｈｅｒｅａｒｅｍａｎｙｓｕｃｃｅｓｓｆｕｌｅｘａｍｐｌｅｓｉ     

SIMULATION OF THE ATOMIZED FLOW BY SLIT TYPE BUCKET ENERGY DISSIPATOR

1.INTRODUCTION Inhydroelectricengineeringifwaterdischar gesfromtheflipbucketatcertainhighspeed,at omizedflowwouldformowingtothespreadingof theaeratedjetandsplashingasthisaeratedjetim pingeswiththewaterdownstream.Thisatomized flowmaythreatenthesafetyofthehydroelectric engineering,sometimesevencausescertainharm sincethisflowmightproduceheavyrainaswellas heavyfoginacertainareajustdownstreamofthe damundertheinfluenceofupstreamwindand downstreamtopography.Thepurposetostudythe atomizedflowisjust…     

NUMERICAL STUDY OF HYDRODYNAMICS OF MULTIPLE TANDEM JETS IN CROSS FLOW

The hydrodynamics of a single jet and four tandem jets in a cross flow are simulated by using the Computational Fluid Dynamics (CFD) software Fluent. The realizable model is used to close the Reynolds-Averaged equations. The flow characteristics of the jets, including the jet trajectory, the velocity field and the turbulent kinetic energy are obtained with various jet-to-cross flow velocity ratios in the range of 2.38-17.88. It is shown that a single jet penetrates slightly deeper than the first jet in a jet group at the same , although the difference decreases with the decrease of . It is also found that the way in which the velo-city decays along the centerline of the jet is similar for both a single jet and the first jet in a group, and the speed of the decay increases with the decrease of . The downstream jets in a group are found to behave differently due to the sheltering effect of the first jet in the group. Compared with the first jet, the downstream jets penetrate deeper into the cross flow, and the velocity decays more slowly. The circulation zone between the two upstream jets in the front is stronger than those formed between the downstream jets. The Turbulent Kinetic Energy (TKE) sees a distinct double-peak across the cross-sections close to each nozzle, with low values in the jet core and high values in the shear layers. The double-peak gradually vanishes, as the shear layers of the jet merge further away from the nozzle, where the TKE assumes peaks at the jet centerline.     

NUMERICAL SIMULATION OF FLOW-INDUCED VIBRATION ON TWO CIRCULAR CYLINDERS IN TANDEM ARRANGEMENT

Flow-induced vibration of two circular cylinders in tandem arrangement elastically mounted with a massspring-damping system was studied by solving the primitive variable Navier Stokes equations incorporating the Arbitrary Lagrangian-Eulerian （ALE） method. The convection term and dissipation term were discretized using the third-order upwind compact scheme and the fourth-order central compact scheme, respectively. The typical spacing between the cylinders is 4 diameters, which is close to the critical value. The dynamic response of the vibrations on two cylinders with two-degreeof-freedom motion is different from that of an isolated cylin der, and also different from that of a cylinder vibrating in the wake of a fixed upstream one. Different flow patterns were found in the wake, and proved to be relevant to the discontinuities observed in the response of the oscillatory cylinders.     

A MODEL FOR PREDICTING PHASE INVERSION IN OIL-WATER TWO-PHASE PIPE FLOW

1. INTRODUCTION Flows consisting of mixtures of two immisciblefluids such as oil and water are encountered frequentlyin many areas of the process industry and in thepetrochemical industry. The phase inversion refers toa phenomenon where, with a small chan…     

THE APPLICATIONS AND STUDY OF NUMERICAL SIMULATION OF TURBULENCE FLOW WITH FREE SURFACE IN HYDRAULIC SPILL WAYS STRUCTURE

The turbulence flow Free Surface has important applications in hydraulic spillways structure,such as the hydraulic jump,energy dissipation flow etc.This is being considered as very complicated flow,and has not yet been solved quite well by numerical method. In this paper,a Large-scale computational software package are developed for numerical laboratory of hydraulic spillway structure.Some methods,such as turbulence model, free surface and irregular boundary treating techniques,scientific computer visualization are put forward and performed.     

THE NUMERICAL CALCULATION FOR THE STERN FLOW OF THREE DIMENSIONAL SURFACE SHIP WITH MULTI-PRO-PELLERS IN OPERATION

In this paper the complex structure and pattern of ship stern flow driven by multi-propellers is simulated numerically by using RANS equations with K-ε turbulence model and propeller lifting surface theory as essential research tool and coupling the computer code of ship stern flow to the computer code of propeller performance prediction through the medium of body force.A ship model with four propellers is selected as the numerical example.Detailed computational results are presented graphically and the qualitative and quantitative analysis is made. Finally,the comparison between the calculated result and the available experimental data is made.The agreement between them is satisfactory.     

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…     

THE GAS-PARTICLE FLOW AND EROSION IN BENDS WITH A RECTANGULAR CROSS-SECTION

1.INTRODUCTIONWallerosionoccursinwidely--usedparticletransportsystems,especiallyatbends,whichconstitutesachallengingengineersproblem.Itisthereforeusefultostudyindetailthegas--particleflowandthewallerosioncausedbytheparticlesfortakingeffectivemeasurestoprotectpipesystemsfromwearing.Theexistingresearchworkfocusedoncurvedpipeswithroundcross--section.Onlyafewauthors,forexample,Mason,etal[3),paidattentiontorectangularcross--section,90"bends.Theirpaperspresentedtheexperimentalresults.Thispaper…