A TURBULENCE MODEL FOR VARYING DENSITY FLOW IN GENERAL CURVILINEAR COORDINATES

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NUMERICAL MODELLING OF FLOW FIELD IN A TIDAL RIVER AND THE NEAR FIELD OF INTAKE FOR A NUCLEAR POWER PLANT

This Paper concerns with the numerical modelling of flow field in a tidal river and in the vicinity ofintake of a nuclear power plant. The hybrid method of fractional steps presented in [1] was adopted in thismodelling. In order to simulate the local flow field nearby the water intake meticulously, the technique ofthe match of the coarse and fine grids was used. The numerical results are in good agreement with thein-situ measurements of the main current. The detailed data of local flow field nearby the intake providesthe assessment of the sediment transport characteristics in the vicinity of intake of the nuclear powerplant.     

THEORY AND NUMERICAL ANALYSIS OF THE INTERACTION BETWEEN TURBULENCE AND SUSPENDED SEDIMENTs

The coupled hydrodynamical-ecological model for Regional and Shelf Seas Coherens was modified through introducing sediment model in order to simulate suspended sediment transport and account for the interaction between turbulence and sediment. To discuss the effects of sediment on vertical eddy viscosity and diffusion coefficients, the damping function of sediment on turbulence was introduced into one equation k-ε turbulence closure model. Moreover, it is assumed that local equilibrium among turbulence production, dissipation and buoyancy destruction exist near the bottom. The local equilibrium assumption is introduced into the one equation k-ε model and the specific formulation of local equilihrium for one equation k-ε was derived. The tidal current was calculated for Youngkwang Bay near the west coast of Korea. Meanwhile, the suspended sediment was also simulated with the local equilibrium assumption and damping function of sediment on turbulence. It is found that the damping function of sediment reduces vertical eddy viscosity and diffusion coefficients. The local equilibrium assumption changes obviously bottom layer turhulence intensity and sediment concentration.     

ON THE FINITE DIFFERENCE METHODS FOR TWO DIMENSIONAL TURBULENCE BOUNDARY LAYER

In this paper,the author first establishes the general finite difference formula for the governing equations ofthe turbulent average velocities in a steady two dimensional incompressible fluid boundary layer-inner layer.Next,three key parameters of the difference scheme are determined respectively by several simple flow models with knownanalytical solutions.Finally a special five points difference system is given and its application value is showed by anumerical example for the vertical velocity distribution in an Ekman's layer.     

THE APPLICATION AND DEVELOPMENT OF TURBULENCE MODELS IN BUOYANT RECIRCULATING FLOWS

In this paper, a modified κ-ε turbulence model, a simplified algebraic stress model and a developed two-fluidmodel have been presented based on numerical modeling of turbulent buoyant recirculating flows. The calculatedresults by these models are in good agreement with experiments. However, the last model is much better forsimulating gravity-stratified flows.     

THE APPLICATION OF COKELET''''S WAVE THEORY IN THE CALCULATION OF WAVE-CURRENT FIELD

By using Cokelet's wave theory,the limiting wave height and the relative waveangular frequency in wave-current field were calculated in this paper.It is indicated by numeri-cal calculation that if the water depth is not too small,the result given by authors'calculationare very close to the results of limiting wave height by Dalrymple(1975)and to the data of rel-ative wave angular frequency by linear wave theory;but if water depth is rather small,thereare some discrepancy,     

A STUDY ON THE MEASURING TECHNIQUES FOR EXCITING FORCE IN CAVITATION TUNNEL

A multi-function sampling system has been set up in Shanghai Ship & ShippingResearch Institute (SSSRI) where a test on the fluctuating pressure of two propeller models werecarried out. This paper deals with a study on the technical problems concerning the measurementand analysis techniques involved in the test. The sampling and processing procedure of signal is one of the major factors affecting the ac-curacy and stability of the prediction of fluctuating pressure induced by propeller. Integral-peri-od sampling, high enough sampling frequency and suitable resolution must be kept in samplingand processing. The procedure of sampling and processing should be validated by standard signalcorresponding to the blade frequency of different orders in comparative tests.     

THE CHARACTERISTICS OF TURBULENCE AND DISPERSION IN SURFACE LAYER OF COASTAL REGION

By analyzing turbulence data measured at two sites in coastal regions of Hangzhoubay,it is discovered that:(1)The turbulent intensity I_k is inversely proportional to the windspeed at lower speed.While at higher wind speed,it keeps basically to be constant.(2)Underthe unstable conditions in the vicinity of sea shore,the dimensionless standard deviations of windspeed σ_k/U(?) are constants basically,while in the inland,they can be described by the expressionssimilar to Panofsky(1977)models but with different constants.Under the stable conditions,they are constants when Z/L<0.2 and proportional to 1/3 power of Z/L for larger Z/L.(3)Near the coast,the variation of U(?)/U with Z/L follows Businger(1971)model U(?)/U =k/(?)(Z/L)very well not only under stable but also under unstable condition.Inland,it is coincidentvery well merely under the condition-1.0≤Z/L≤0.3.Out this range,the deviation islarge.(4)The dispersion parameters can be described in the form recommended by Draxler(1976)but with different constants.Under the unstable condition,they can also be expressed asBriggs(1985)model with different constants.     

THE LINEAR SEPARATED FLOW MODEL FOR TWO－PHASI FLOW INSTABILITY IN BOILING CHANNELS

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A LATTICE BOLTZMANN MODELING FOR THE WESTERN BOUNDARY CURRENT IN A LINEAR WIND-DRIVEN QUASI-GEOSTROPHIC MODEL

1 .　INTRODUCTIONLatticeBoltzmannMethod (LBM )isanewnumericalmethodforcomputationalfluid (ChenandDoolen 1998) ,whichisdevelopedfromLat ticeGasCellularAutomaton (LGCA )inthelate80satlastcentury .LBMusesthecontinuousdistri butionfunctiontoreplacetheBooleanvariablesusedinLGCA .Asaresult ,LBMovercomesmanyshortcomingsofitsancestor ,suchasnoise ,notconformingtoGalileoinvarianceetc .HeandLuo(1997)developedLBMasaself containedsystemconstructedtheamodelwithoutconnectiontoLGCA .LBMha…     

THEORY AND NUMERICAL ANALYSIS OF THE INTERACTION BETWEEN TURBULENCE AND SUSPENDED SEDIMENT

1.INTRODUCTIONThe damping function of sedi ment on turbu-lence becomes an obvious phenomenon near thebottom where sedi ment induced density stratifica-tion is usually significant.The vertical sedi mentdiffusion coefficient has inti mate relationto turbu-lence.So the damping function has i mportanteffect on sedi ment transport.Many researchershave paid much attention to the interaction be-tween turbulence and suspended sedi ment since theability to accurately predict the sedi ment transpor…     

SECOND-ORDER MOMENT TWO-PHASE TURBULENCE MODEL ACCOUNTING FOR TURBULENCE MODULATION IN SWIRLING SUDDEN-EXPANSION CHAMBER

A semi-empirical turbulence enhancement model accounting for the particle-wake effect was incorporated into the second-order moment two-phase turbulence model and employed to simulate gas-particle flows in a swirling sudden-expansion chamber. The simulated results for two-phases mean velocities and fluctuation velocities coincide well with the experiment ones, which demonstrates that this model, in comparison with the turbulence model not accounting for the wake effect, leads to higher calculating accuracy.     

NUMERICAL SIMULATION FOR THE STEPPED SPILLWAY OVERFLOW WITH TURBULENCE MODEL

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THE TURBULENCE CHARACTERISITICS OF OPEN CHANNEL FLOW

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A SECOND-ORDER MOMENT TURBULENCE MODEL FOR POWER LAW FLUID WITH PARTICLES

The USM-θ model of power law fluid for dense two-phase turbulent flow was developed, which combines the unified second-order moment model for two-phase turbulence with the particle kinetic theory for the inter-particle collision. This model was used to simulate the turbulent flow of power law fluid single-phase in pipe. It is shown that the USM ? θ model has better prediction result than the k f ? ε f?kp?εp?θ model. The USM ? θ model was then used to simulate the dense two-phase turbulent up flow of power law fluid with particles. With the increase of the flow exponent, the velocities of power law fluid and particles increase near the pipe centre. Comparison between the two-phase flow of power law fluid-particle and of liquid-particle indicates that the axial fluctuation velocity of fluid phase and particle phase in liquid-particle two-phase flow is smaller than that in the power law fluid two-phase flow, but the two-phase velocities of power law fluid-particle and liquid-particle are close to each other.     

THE NUMERICAL SIMULATION OF TWO-DIMENSIONAL OPEN CHANNEL TURBULENCE

A numerical simulation on 2-D open channel turbulence using the two-equationturbulent model(k-e model) is made.The diseretization equations of depth-averaged 2-D differ-ential equation are obtained by the control-volume formulation.Some examples including theflows in straight open channel,symmetry sudden expansion and one-side sudden expansion arecalculated by using the SIMPLE algorithm.The distributions of the flow velocity u,the kineticturbulent energy k,and the turbulent viscosity μ,etc.are obtained.The numerical calculationsindicate a good agreement with experimental data and other turbulent models calulations.     

TURBULENCE MEASUREMENT INSTRUMENT WITH A SILICON PIEZORE-SISTANCE BEAM

A newly developed turbulence measurement instrument is introduced in the paper.The transducer of the device is based on the principle of the effect of silicon piezoresistance that isintegrated in a Wheatstone bridge on a pure silicon beam. At one end of the beam, a small lightball is installed as the target forced by the water flow. The other parts are prevented from thewater flow with a sophisticated stainless steel tube. The instrument can be used to measure turbu-lent velocities either in clear Water or in flows bearing hyperconcentration of sediment. It can al-so be used to measure velocities in both glass flume and model experiments as well as in pipe ex-periment by being mounted in a special way.