ON INSTABILITY OF DILUTE FIBER SUSPENSIONS IN AN AXISYMMETRIC TAYLOR-COUETTE FLOW

1. INTRODUCTION The shear-driven flow between independently rotating concentric cylinders is named as Taylor- Couette flow after the standout work of Taylor in 1923 and his later research in this field. Since then,there have been alot of literatures relatedto this problem. Among them,the hydrodynamic in- stability of Taylor-Couette flowin the Newtonian fluid has been one of the most attractive topics . The review written by Tagg[1]has summarized these fruits .Inrecent years ,theinstabi…     

NUMERICAL SIMULATION OF LAMINAR SQUARE IMPINGING JET FLOWS

A theoretical study has been undertaken to determine the flow characteristics associated with a three-dimensional laminar impinging jet issuing from a square pipe nozzle. Interesting flow structures around the jet are detected. The numerical result reveals the existence of four streamwise velocity off-center peaks near the impingement plate, which is different from the rectangular jet impingement. The mechanism of the formation of the off-center velocity peaks and the parameters affecting the flow-field characteristics are discussed by comparison of the computed results with different nozzle-to-plate spacings and Reynolds numbers.     

NUMERICAL STUDY OF FLOW AND DILUTION BEHAVIOR OF RADIAL WALL JET

The radial wall jet is a flow configuration that combines the radial jet and the wall jet. This article presents a simulation of the radial wall jet by applying the transition Shear-Stress Transport (SST) model. Tanaka's experimental data are used for validation. The computed velocity profiles agree well with the experimental ones. The distributions of the velocity on cross-sections show a similarity in the main region and the profiles are different with those of the free radial jet or the wall jet, because the presence of the wall limits the expansion of the jet. By introducing the equivalent nozzle width, the maximum velocity decays and the half-width distributions are normalized, respectively. In addition to compare the flow field with experiments, this paper also analyzes the dilution effect of radial wall jets in terms of the concentration distributions. The concentrations on the wall keep constant within a certain distance from the nozzle. And the concentration distributions also show a similarity in the main region. Both the decays of the maximum concentration and the distributions of the concentration half-width fall into a single curve, respectively. The dilution effect of radial wall jets is thus verified.     

RESEARCH ON MOTION CHARACTERISTICS OF GAS-SOLID JET FLOW

l.INThoDUCT1ONTheresearchontwo-phasejetflowisbecomingahotspotofjetflowresearchinrecentyears.Therapiddevelopmentofcomputertechnologyhasmadeitpossibletosimulatetwo-phasejetflow,whichisofessentialimPortanceinvariousengineeringapplications.Forin-stanceitisausualproceduretospoutparticlesintoreactororcombustorinengineering.Theeffectofflowonparticlesdeterminestheparticledistributionandthepresenceofparticleshaveeffectonjetflowinturn.Therefore,theinvestigationontheparticledistributionandtheflowchar…     

NUMERICAL STUDY OF FLOW PAST AN AXISYMMETRIC BODY WITH A RING WING AT VARIOUS ATTACK ANGLES

1 .　INTRODUCTIONFortraditionalbody fittedgridsystemusedtocomputetheflow pasttheaxisymmetricbody ,thesingularityonthelongitudinalaxisisalongstand ingobstacle .Rationalsolutionishardtobeachievedevenwithfinemeshesgeneratedwithinthevicinityofthelongitudinalaxis .Hence ,appro priategridsystemisreguiredtoavoidthesingulari ty .Extensivenumericalexperimentsareconductedtoobtainthedesired gridsysteminthis paper .BasedontheideaofDDM[1] ,theoriginalflowfieldofthebodyisdividedinto 8sub domainsac cor…     

THEORETICAL AND EXPERIMENTAL STUDY ON THE CONICAL SWIRLING WATER JET FLOW

This paper is concerned with theoretical and experimental study on theconical swirling water jet flow.Based upon the theoretical analysis,the experiment on thestructural characteristics of swirling water jet flow including the velocity and pressure dis-tribution laws,on which the parameters of the jet,nozzle and directional blades havemore or less influence,was carried out in CSSRC by using a 3-D LDV in order to optimizea new high-efficiency jet instead of swirling drilling bit for rock-breaking and continuouslydrilling,and to meet the demand of radial horizontal drilling technology.Meanwhile basedon the experimental results,the numerical simulation was conducted for the conicalswirling water jet in the immersed well-bottom flow by solving the RANS equations in the3-D body-fitted coordinate system with the k-ε turbulence model.The numerical resultsare consistent with the experimental data,and lead to some conclusions which are impor-tant for applying the conical swirling water jet to the petroleum drill     

HYDRODYNAMICS STABILITY OF BICKLEY JET WITH PARTICLE LADEN FLOW

The stability of Bickley jet with particle laden flow is investigated numerically. The stability characteristics are calculated for various Stokes numbers and particle concentrations. The results confirm the author's early calculations, which also shows that the numerical program is reliable. It is further shown that there is a critical value for the effect of Stokes number, which is about 2. The most damped mode occurs when Stokes number is of order of 10 for different particle concentrations and depends weakly on the wave number. The difference in the eigenfunctions and its derivatives between the particle-laden flow and the clean gas flow is insignificant for fine particles, while the difference for coarse particles is significant.     

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

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

AN EXPERIMENTAL AND NUMERICAL INVESTIGATION OF THE STARTING FLOW OF A UNIFORMLY ACCELERATING CIRCULAR CYLIINDER

The starting flow around a uniformly accelerated circular cylinder is investigatedby flow visualization techncque and solving N-S equations numerically in detail.The results ofthe starting flow are similar with those of the impulsively started one.At lower Re_α,numbers the“phenomenon a”is revealed;the“phenomenon β”appears at higher Re_α numbers,but withonly one secondary vortex.At the early stage of the starting vortex formation,the flow islaminar;at the later stage,the flow transforms into turbulent flow.The velocity distribution inthe flow field is measured with the multiwires installment.The calculational results are comparedwith the results of experiment,and both are in agreement with each other.     

THE COMBINED EFFECTS OF FLOW REGULATION AND AN ARTIFICIAL FLOW RELEASE ON A REGULATED RIVER

Damming and regulating the flow of rivers is a widespread issue and can have a significant impact on resident biota. The Tongariro River, central North Island, New Zealand, has a flow regime that is regulated by two hydroelectric dams along its length, and it has been suggested that ‘flushing flows’ would assist benthic communities by removing ‘nuisance’ periphyton growth forms that typically occur in autumn. We assessed whether (i) damming has altered periphyton and macroinvertebrate communities downstream of the Rangipo Dam and (ii) whether the release of a flow pulse equivalent to 50 times the baseflow is sufficient to (a) move the substrate in the section of river downstream of this dam and (b) impact benthic periphyton and macroinvertebrate communities. Downstream macroinvertebrate communities were impacted by the presence of the dam, but periphyton was not. No movement of substrate occurred downstream of the dam as a result of the flow release, which was likely because of naturally high embeddedness and armouring of substrate. Periphyton biomass and macroinvertebrate density were not affected by the release indicating that larger releases would be required to have any effect on benthic communities downstream of this dam. This study highlights the importance of considering natural bed structure and sediment dynamics when using flow releases downstream of dams to control periphyton. Copyright © 2013 John Wiley & Sons, Ltd.     

EXPERIMENTAL STUDY ON THE EFFECTS OF AIR ENTRAINMENT ON A PLANE JET DIFFUSION IN A PLUNGE POOL

l'mTRODUrmNThisworkwasmotivatedbythepotentialapplicationOftheerosionofplungepoolsdownstreamofdamscausedbysubmergedwaterjets.TheerosionorscourofplungepoolsoccursatthePointofajetimpact.Thescourprocesshasbeeninvestigatedformanyyears.Thescourdepthestimatedfromformulasdevelopedoveryears,however,indicatesawidevariation(MasonandArumugam,l985)-Mostoftheseformulasinvolveanexpressioninwhichscourdepthisafunctionofthedischargeperunitwidth,theheaddropandthechar-acteristicsizeofthebedmaterial.Arecentin…     

AN EXPERIMENTAL STUDY OF FLOW FIELD IN THE FLUID HOMOGENIZER

A Laser Doppler Anemometer (LDA) is used to measure and study the flow field in the working chamber of a homogenizer. Flow Patterns, distributions of mean and fluctuating velocities, shear rates are obtained in details. The characteristics of the flow field and the basic principles of homogenizing are presented. These results are very helpful for the improvement of fluid homogenizers.     

THE FLUCTUATION CHARACTERISTICS OF NATURAL AND VENTILATED CAVITIES ON AN AXISYMMETRIC BODY

Natural and ventilated cavitations generated on a smooth-nosed axisymmetric body were studied experimentally. The characteristics of small scale and localized fluctuations of “steady cavities” were measured by pressure transducers. Comparisons between natural and ventilated cavities at different measured points for several cavitation numbers were done. It was observed that the dominant fluctuations were concen trated in the frequency range of 0Hz 50Hz for all the cavitation cases, Similar shapes and magnitudes of the frequency spectra were detected for both natural and ventilated cavities.Much larger spectral amplitude in the cavity closure region suggested as fluctuations source. From partial cavitating flow to supercavitating flow, the dominant frequency and the corre sponding amplitude decreased with decreasing cavitation number, which meant that cavity became more steady while developing.     

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 …     

EVALUATION OF HFAM ON A FLOW OVER A BACKWARD－FACING STEP

ＥＶＡＬＵＡＴＩＯＮ　ＯＦ　ＨＦＡＭ　ＯＮ　Ａ　ＦＬＯＷ　ＯＶＥＲ　Ａ　ＢＡＣＫＷＡＲＤ－ＦＡＣＩＮＧ　ＳＴＥＰＥＶＡＬＵＡＴＩＯＮＯＦＨＦＡＭＯＮＡＦＬＯＷＯＶＥＲＡＢＡＣＫＷＡＲＤ－ＦＡＣＩＮＧＳＴＥＰ￥ＺｈａｎｇＸｉａｏ－ｙｕａｎ；ＬｉＷｅｉ（...     

INVESTIGATION ON THE SPLASH LENGTH OF THE AERATED JET

Atomized flow forms as an aerated jet from high dams impacts against the downstream water surface at high speed. Of all the regions of atomized flow the splash region is in the center of storm rainfall, which might cause certain damage to the hydropower stations and thence more attention should be paid. In this paper the impact of the water drop at the outer edge of the aerated jet against the downstream water surface was analyzed, and the motion of the splash water drop was investigated. Furthermore, a new formula for the calculation of the splash length was suggested, which is in good agreement with the data of model tests and prototype observation.     

AN EXPERIMENTAL STUDY ON THREE DIMENSIONAL STRUCTURE OF BAROCLINIC WAVY JET STREAM IN A ROTATING ANNULUS SUBJECT TO RADIAL TEMPERATURE GRADIENT

1.　INTRODUCTIONThe research on jet,which is a typical flow pattern in atmosphere,has made a greatprogress in both theory and observation.There existsa striking similar feature between thejetstream of baroclinic fluid in a rotating annulussystem and the defined one of IMO( Inter-national Meteorological Organization,Upper Air Technical Commission) .Forsuch a similarfeature,more and more attention hasfocused on the experimental simulation of jetstream ina baroclinic fluid system based on…     

AN INTEGRATEDC METHOD FOR COMPUTING COMPUTING THE INTERNAL AND EXTERNAL VISCOUS FLOW FIELD AROUND THE DUCTED PROPULSOR BEHIND AN AXISYMMETRIC BODY

ＡＮＩＮＴＥＧＲＡＴＥＤＣＭＥＴＨＯＤＦＯＲＣＯＭＰＵＴＩＮＧＣＯＭＰＵＴＩＮＧＴＨＥＩＮＴＥＲＮＡＬＡＮＤＥＸＴＥＲＮＡＬＶＩＳＣＯＵＳＦＬＯＷＦＩＥＬＤＡＲＯＵＮＤＴＨＥＤＵＣＴＥＤＰＲＯＰＵＬＳＯＲＢＥＨＩＮＤＡＮＡＸＩＳＹＭＭＥＴＲＩＣＢＯＤ...     

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.     

EXPERIMENTAL STUDY ON VELOCITY PROFILE OF SUBMERGED ABRASIVE SUSPENSION JET FLOW

1. INTRODUCTIONAbrasive Water Jet (AWJ), has been developed the into a remarkable and extensively used cutting technology in last two decades. In recent years, the polymer PAM has generally been applied to jetting fluid to further increase the abrasive ve…