AN EXTENDED k-ε MODEL FOR NUMERICAL SIMULATION OF WIND FLOW AROUND BUILDINGS

I.IntroductionWindvelocitiesaroundbuildingsandwind-inducedpressuresonbuildingsurfaceareimportantparametersforbuildingdisign.Withtherapidadvanceofcomputertechnology,ithasbecomepossibletoevaluatethethree-dimensionalwind-turbulentflow'sbyusingnumericalsimulationtechniques.Atpresent.awidevarietyofnumericalapproacheshavebeendevelopedanddifferenttypesofturbulencemodellinghavebeenappliedforthepredictionofwindflowphenomena.Amongtheseapproaches,thenumericalsimulationbasedonthesteadyReynold'saveragedN…     

NUMERICAL SIMULATION OF COMPLICATED PIPE FLOW WITH k-εMODEL

In this paper, turbulence in a complicated pipe is simulated by using the k-ε model. The ladder-like mesh approximation is used to solve the problem of complicated boundary with the result of numerical simulation favorable. Two computational examples are given to validate the strong adaptability and stability of k-ε model.     

NUMERICAL SIMULATION OF COMPLICATED PIPEFLOW WITH k-εMODEL

l.IntroductionInenginecringandnaturallie1ds.therearemanycomplicatedpipel1owswlthcomplexboundariesandobstructionsinsidethepipesimultaneously.IfthesimuIationofabodyconforminggridisuscdtosolvCthcscprobIems.itwouldbeveryIaboriousanddif1iculttoinsurestabilityandconvergence.Thus.weneedasimplcandapplicabIe1nethodtosimuIatctheboundariesapproximatelysothatk--emodetmaybeused.Ladder-1ikcmeshisusedinthispapertoreplacecomplexboundaryconditions.Meanwhile.blockoffmethodisusedforobstructedregion.II.Mathem…     

NUMERICAL SIMULATION OF WING-BODY JUNCTION TURBULENCE FLOW

Wing-body junction turbulence flow is simulated by using RANS equation and boundary fitted coordinate technique.Three order differential scheme is used in the computation of convection term and two layers turbulence model are employed in the calculation.     

NUMERICAL SIMULATION OF FLOW OF HIGHLY VISCOELASTIC FLOW IN THREE－DIMENSIONAL VARYING THICK SLIT CHANNEL

（杨伯源）（李勇）ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＦＬＯＷＯＦＨＩＧＨＬＹＶＩＳＣＯＥＬＡＳＴＩＣＦＬＯＷＩＮＴＨＲＥＥ－ＤＩＭＥＮＳＩＯＮＡＬＶＡＲＹＩＮＧＴＨＩＣＫＳＬＩＴＣＨＡＮＮＥＬ￥ＹａｎｇＢｏｙｕａｎ；ＬｉＹｏｎｇ（Ｄｅｐａｒｔ...     

MODIFICATION OF THE κ-ε TURBULENCE MODEL FOR SWIRLING RECIRCULATING FLOW IN A PIPE EXPANSION

SUMMARY

A modified turbulence model, incorporating anisotropic effects into the standard κ-ε model, is proposed for the numerical simulation of swirling recirculating flow in a pipe expansion. The new modification follows the concept that the correction to the standard κ-ε model is made only in the flow regions where the anisotropic effects are appreciable. The performance of the present hybrid κ-ε model for two swirling flows with moderate and high swirl levels is better than that of the standard κ-ε model and the modified κ-ε model proposed by Abujelala and Lilley and is also competitive with our previously developed hybrid κ-ε model. Moreover, the present hybrid modification provides a relatively simpler form compared to our previously developed model; this also helps alleviate the numerical instability in the calculation procedure. Encouraging improvement in the prediction of the size of the central toroidal recirculation zone using the present hybrid modification is also exhibited     

NUMERICAL SIMULATION OF THREE DIMENSIONAL GAS-PARTICLE FLOW IN A SPIRAL CYCLONE

The three-dimension gas-particle flow in a spiral cyclone is simulated numerically in this paper. The gas flow field was obtained by solving the three-dimension Navier-Stokes equations with Reynolds Stress Model (RSM). It is shown that there are two regions in the cyclone, the steadily tangential flow in the spiral channel and the combined vortex flow in the centre. Numerical results for particles trajectories show that the initial position of the particle at the inlet plane substantially affects its trajectory in the cyclone. The particle collection efficiency curves at different inlet velocities were obtained and the effects of inlet flow rate on the performance of the spiral cyclone were presented. Numerical results also show that the increase of flow rate leads to the increase of particles collection efficiency, but the pressure drop increases sharply.     

STOCHASTIC ALGORITHM AND NUMERICAL SIMULATION FOR DROP SCAVENGING OF AEROSOLS

The time evolution of aerosol size distribution during precipitation, which is founded mathematically by general dynamic equation (GDE) for wet removal, describes quantitatively the process of aerosol wet scavenging. The equation depends on aerosol size distribution, raindrop size distribution and the complicated model of scavenging coefficient which is induced by taking account of the important wet removal mechanisms such as Brownian diffusion, interception and inertial impaction. Normal numerical methods can hardly solve GDE, which is a typical partially integro-differential equation. A new multi-Monte Carlo method was introduced to solve GDE for wet removal, and then was used to simulate the wet scavenging of aerosols in the real atmospheric environment. The results of numerical simulation show that, the smaller lognormal raindrop size distribution and lognormal initial aerosol size distribution, the smaller geometric mean diameter or geometric standard deviation of raindrops can help scavenge small aerosols and intermediate size aerosols better, though large aerosols are prevented from being collected in some ways.     

NUMERICAL SIMULATION FOR A PROCESS ANALYSIS OF A COKE OVEN

A computational fluid dynamic model is established for a coking process analysis of a coke oven using PHOENICS CFD package. The model simultaneously calculates the transient composition, temperatures of the gas and the solid phases, velocity of the gas phase and porosity and density of the semi-coke phase. Numerical simulation is illustrated in predicting the evolution of volatile gases, gas flow paths, profiles of density, porosity of the coke oven charge, profiles of temperatures of the coke oven gas and the semi-coke bed. On the basis of above modeling, the flow of coke oven gas （COG） blown from the bottom of the coke oven into the porous semi-coke bed is simulated to reveal whether or not and when the blown COG can uniformly flow through the porous semi-coke bed for the purpose of desulfurizing the semi-coke by recycling the COG. The simulation results show that the blown COG can uniformly flow through the semi-coke bed only after the temDerature at the center of the semi-coke bed has risen to above 900℃.     

NUMERICAL SIMULATION OF INSECT FLIGHT

In the non-inertial coordinates attached to the model wing, the two-dimensional unsteady flow field triggered by the motion of the model wing, similar to the flapping of the insect wings, was numerically simulated. One of the advantages of our method is that it has avoided the difficulty related to the moving-boundary problem. Another advantage is that the model has three degrees of freedom and can be used to simulate arbitrary motions of a two-dimensional wing in plane only if the motion is known. Such flexibility allows us to study how insects control their flying. Our results show that there are two parameters that are possibly utilized by insects to control their flight: the phase difference between the wing translation and rotation, and the lateral amplitude of flapping along the direction perpendicular to the average flapping plane.     

KINEMATIC WAVE PROPERTIES OF ANISOTROPIC DYNAMICS MODEL FOR TRAFFIC FLOW

ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｃｅｎｔｌｙｔｈｅａｕｔｈｏｒｓｐｒｅｓｅｎｔｅｄａｎｅｗｄｙｎａｍｉｃｓｍｏｄｅｌｆｏｒｔｒａｆｆｉｃｆｌｏｗ[1].Ｔｈｅｍｏｄｅｌｃｏｍｐｒｉｓｅｓａｃｏｎｔｉｎｕｕｍｅｑｕａｔｉｏｎａｎｄａｄｙｎａｍｉｃｓｅｑｕａｔｉｏｎ ｋ/ ｔ+ (ｋｕ) / ｘ=0 ,( 1 ) ｕ ｔ+ｕ ｕ ｘ=ｕｅ(ｋ) -ｕＴ +ａ ｕ ｘ,( 2 )ｗｈｅｒｅｋｉｓｔｒａｆｆｉｃｄｅｎｓｉｔｙ ;ｕｉｓｍｅａｎｓｐｅｅｄ ;ｘ ,ｔａｒｅｓｐａｃｅａｎｄｔｉｍｅｃｏｏｒｄｉｎａｔｅｓｒｅｓｐｅｃｔｉｖｅｌｙ .Ｔｉｓｒｅｌ…     

NUMERICAL SIMULATION OF THREE DIMENSIONAL TURBULENT FLOW IN SUDDENLY EXPANDED RECTANGULAR DUCT

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＴＨＲＥＥＤＩＭＥＮＳＩＯＮＡＬＴＵＲＢＵＬＥＮＴＦＬＯＷＩＮＳＵＤＤＥＮＬＹＥＸＰＡＮＤＥＤＲＥＣＴＡＮＧＵＬＡＲＤＵＣＴＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＴＨＲＥＥＤＩＭＥＮＳＩＯＮＡＬＴＵＲＢＵ...     

A MODEL FOR SIMULATION OF FRICTION PHENOMENON BETWEEN DIES AND WORKPIECE

Based on the interaction of asperities and upperbound approach a mathematical model for simulation of friction phenomenon between dies and workpiece is proposed.Optimizing the mathematical model with respect to several variables it is found that in addition to adhering, tearing, ploughing, etc., asperities workpiece can move wave-like along the surface layer and under certain circumstances they may disappear. If the asperities wavily move along the surface layer the friction coefficient depends on the geometry of asperities. However,the bonding strength of asperities has no significant influence on friction coefficient. The depth of the plastic deformation layer is related to the geometry of asperities, too.The soundness of the prerequisite of the proposed model and some analytical results were verified by experiments.     

PROBABILITY MODEL AND SOLUTION ON EARTHQUAKE EFFECTS COMBINATION IN ALONG WIND RESISTANT DESIGN OF TALL-FLEXIBLE BUILDINGS

A model on the earthquake effects combination in wind resistant design of high-rise flexible structures is proposed in accordance with the probability method. Based on the Turkstra criteria, the stochastic characters of wind velocity, earthquake ground acceleration and excitations occurrence probability are taken into account and then the combination of the earthquake effects in structure wind resistant design is analyzed with the convolution approach. The results indicate that as for the tall flexible buildings whose lateral force is governed by wind loading, the maximum lateral loads verification with respect to the wind resistant design combined with earthquake effects may be more unfavorable compared with that in terms of the earthquake resistant design involving wind effects.     

NUMERICAL SIMULATION OF SWIRLING FLOWS IN OXIDATION REACTORS FOR TiO2 MANUFACTURE

The oxidation reactor plays a key role in producing rutile titanium dioxide （TiO2） from vapor-phase titanium tetrachloride （TiCl4） by employing a swirling flow operation for enhanced gas mixing. This work aims to understand the effect of reactor configuration on the 3-D swirling flow field using computational fluid dynamics （CFD） simulation. Considering the anisotropic turbulence involved, the Reynolds stress model is applied to describe the complex swirling flow together with the cross-flow mixing of gases. The results show significant effect of the flow angle between the wall jet of air stream （representing TiCl4 in practice） and the axial direction on the initial flow field of cross-flow mixing, where 60° gives smooth profiles of axial velocity development while 90° may provide the fastest mixing between the jet and the axial bulk flow. The pipe shape for the reaction and developing zone, i.e., straight, expanding and shrinking, shows slight influence on the hydrodynamics.     

A THREE-FLUID MODEL OF THE SAND-DRIVEN FLOW

ＡＴＨＲＥＥ－ＦＬＵＩＤＭＯＤＥＬＯＦＴＨＥＳＡＮＤ－ＤＲＩＶＥＮＦＬＯＷ￥(刘大有，董飞)ＬｉｕＤａｙｏｕ；ＤｏｎｇＦｅｉ（ＩｎｓｔｉｔｕｔｅｏｆＭｅｃｈａｎｉｃｓ，ＡｃａｄｅｍｉａＳｉｎｉｃａ，Ｂｅｉｊｉｎｇ１０００８０，Ｐ．Ｒ．Ｃｈｉｎａ）Ａｂｓ...     

NUMERICAL SIMULATION OF OIL MIGRATION-ACCUMULATION OF MULTILAYER AND ITS APPLICATION

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｏｉｌｆｏｒｍａｔｉｏｎｉｎｓｅｄｉｍｅｎｔｂａｓｉｎｓ ,ｉｔｓｄｉｓｐｌａｃｅｍｅｎｔ,ｔｒａｎｓｐｏｒｔａｎｄａｃｃｕｍｕｌａｔｉｏｎ ,ａｎｄｔｈｅｆｉｎａｌｆｏｒｍａｔｉｏｎｏｆｏｉｌｄｅｐｏｓｉｔｓｈａｖｅｂｅｅｎｏｎｅｏｆｔｈｅｋｅｙｐｒｏｂｌｅｍｓｉｎｔｈｅｅｘｐｌｏｒａｔｉｏｎｏｆｏｉｌ＿ｇａｓｒｅｓｏｕｒｃｅｓ.Ｈｏｗｈａｓｏｉｌｂｅｅｎａｃｃｕｍｕｌａｔｅｄｉｎｔｈｅｐｒｅｓｅｎｔｌｏｏｐａｃｃｏｒｄｉｎｇｔｏｔｈｅｍｅｃｈａｎｉｃｓｏｆｉｍｍｉｓｃ…     

SECOND-ORDER MOMENT MODEL FOR DENSE TWO-PHASE TURBULENT FLOW OF BINGHAM FLUID WITH PARTICLES

The USM-θmodel of Bingham fluid for dense two-phase turbulent flow was developed, which combines the second-order moment model for two-phase turbulence with the particle kinetic theory for the inter-particle collision. In this model, phases interaction and the extra term of Bingham fluid yield stress are taken into account. An algorithm for USM-θmodel in dense two-phase flow was proposed, in which the influence of particle volume fraction is accounted for. This model was used to simulate turbulent flow of Bingham fluid single-phase and dense liquid-particle two-phase in pipe. It is shown USM-θmodel has better prediction result than the five-equation model, in which the particle-particle collision is modeled by the particle kinetic theory, while the turbulence of both phase is simulated by the two-equation turbulence model. The USM-θmodel was then used to simulate the dense two-phase turbulent up flow of Bingham fluid with particles. With the increasing of the yield stress, the velocities of Bingham and particle decrease near the pipe centre. Comparing the two-phase flow of Bingham-particle with that of liquid-particle, it is found the source term of yield stress has significant effect on flow.     

A NON－INCREMENTAL TIME－SPACE ALGORITHM FOR NUMERICAL SIMULATION OF FORMING PROCESS

ＡＮＯＮ－ＩＮＣＲＥＭＥＮＴＡＬＴＩＭＥ－ＳＰＡＣＥＡＬＧＯＲＩＴＨＭＦＯＲＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＦＯＲＭＩＮＧＰＲＯＣＥＳＳＬｉｕＢａｏｓｈｅｎｇ（柳葆生）ＣｈｅｎＤａｐｅｎｇ（陈大鹏）ＬｉｕＹｕ（刘渝）（ＲｅｃｅｉｖｅｄＡｐｒ...     

ON THE APPLICATION OF ADI METHOD TO NUMERICAL SIMULATION OF THE MARANGONI CONVECTION CONTROLLING IN LIQUID BRIDGE MODEL

An ADI scheme is suggested to simulate the Marangoni convection controlling with emphasis on investigating application of the technique numerically. Numerical experiments conducted in the present paper turn out both successful and efficient. Hence, ADI scheme is expected to be extended to the study of other convection processes related to material manufacturing.