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.     

A NEW TURBULENCE MODULATION IN SECOND-ORDER MOMENT TWO-PHASE MODEL AND ITS APPLICATION TO HORIZONTAL CHANNEL

A new second-order moment two- phase turbulence model accounting for particle wake effect was established and used to simulate gas-particle flow in a horizontal channel for different values of wall roughness. The results show that compared with the model without considering the particle wake effect, the present model gives simulation results agreeing much better with the experimental results for the gas turbulence modulation, but the predicted results for particle motion with the two kinds of models are quite close.     

A TURBULENCE MODEL FOR VARYING DENSITY FLOW IN GENERAL CURVILINEAR COORDINATES

ＡＴＵＲＢＵＬＥＮＣＥＭＯＤＥＬＦＯＲＶＡＲＹＩＮＧＤＥＮＳＩＴＹＦＬＯＷＩＮＧＥＮＥＲＡＬＣＵＲＶＩＬＩＮＥＡＲＣＯＯＲＤＩＮＡＴＥＳＺｈｅｎｇＢａｎｇ－ｍｉｎｇ；ＹａｎｇＸｉａｏ－ｔｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＲｉｖｅｒＥｎｇｉｎｅｅｒｉｎｇ...     

NUMERICAL SIMULATION FOR THE STEPPED SPILLWAY OVERFLOW WITH TURBULENCE MODEL

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｓｔｅｐｐｅｄｓｐｉｌｌｗａｙｈａｄｂｅｅｎｕｓｅｄａｔｔｈｅｂｅｇｉｎｎｉｎｇｏｆｔｗｅｎｔｙｃｅｎｔｕｒｙ[1 ] .Ｉｎ 1 971 ,Ｅｓｓｅｒｙｅｔａｌ.[2 ] ｃｏｎｄｕｃｔｅｄａｍｏｄｅｌｔｅｓｔｆｏｒｔｈｅｄｅｓｉｇｎｏｆ     

NUMERICAL SIMULATION OF FLOWS FOR SECOND-ORDER VISCOELASTIC FLUID COUPLED WITH HEAT TRANSFER BY DIFFERENTIAL QUADRATURE METHOD

The problem of two-dimensional steady flow of an incompressible second-order viscoelastic fluid coupled with heat transfer between parallel plates was considered. A viscous dissipation function was included in the energy equation.When the elastic property of the fluid is weaker, the zerothorder and first-order approximate governing equations were obtained by means of the perturbation method. To understand the behavior of flow near the tube wall, the half-domain was divided into two sub-domains, in which one is a thin layer near the wall called the inner domain and the remainder is called the outer domain. The governing equations in the inner domain and in the outer domain were discretized respectively by using the Differential Quadrature Method (DQM). The matching conditions at the interface between the inner and outer domains were presented. An iterative method for solving these discretized equations was given in this paper. The numerical results obtained agree with existing results.     

EFFECT OF NON-SPHERICAL PARTICLES ON THE FLUID TURBULENCE IN A PARTICULATE PIPE FLOW

In the non-spherical particulate turbulent flows,a set of new fluid fluctuating velocity equations with the nonspherical particle source term were derived, then a new method,which treats the slowly varying functions and rapidly varying functions separately, was proposed to solve the equations, and finally the turbulent intensity and the Reynolds stress of the fluid were obtained by calculating the fluctuating velocity statistically. The equations and method were used to a particulate turbulent pipe flow. The results show that the turbulent intensity and the Reynolds stress are decreased almost inverse proportionally to the fluctuating velocity ratio of particle to fluid. Nonspherical particles have a greater suppressing effect on the turbulence than the spherical particles. The particles with short relaxation time reduce the turbulence intensity of fluid, while the particles with long relaxation time increase the turbulence intensity of fluid. For fixed particle and fluid, the small particles suppress the turbulence and the large particles increase the turbulence.     

A HYBRID MODEL FOR THE MERGING OF JETS IN A COFLOWING AMBIENT FLUID

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＧｅｎｅｒａｌｌｙｔｈｅｄｉｓｐｅｒｓｉｏｎｏｆｊｅｔｓａｎｄｐｌｕｍｅｓｉｎａｍｏｖｉｎｇｅｎｖｉｒｏｎｍｅｎｔｃａｎｂｅｒｅｌａｔｅｄｔｏｔｈｅｄｉｓｐｏｓ ａｌｏｆｕｒｂａｎａｎｄｉｎｄｕｓｔｒｉａｌｗａｓｔｅｗａｔｅｒ     

A NUMERICAL MODEL FOR 3-D FLOW IN OPEN CHANNELS

A 3-D model based on the Reynolds equations with closed k-ε turbulence model ispresented in this paper,which can be used to predict surface water flow in open channels.In-stead of the“rigid lid”approximation,the solution of the free surface equation is implemented inthe velocity-pressure iterative procedure on the basis of the conventional SIMPLE method.Thismodel was used to compute the flow in rectangular channels with trenches dredged across the bot-tom.The velocity,eddy viscosity coefficient,turbulent shear stress,turbulent kinetic energyand elevation of the free surface over the trenches dredged in the main channel,can be obtained.The computed results are in good agreement with existing experimentaing data.     

ON THE FILTRATION OF NON-NEWTONIAN FLUID IN POROUS MEDIA WITH A MULTIPLE PARAMETER MODEL

ＮＯＭＥＮＣＬＡＴＵＲＥＡＥｍｐｉｒｉｃａｌｃｏｅｆｆｉｃｉｅｎｔ ,ｋｇ/ (ｓｍ)ＢＥｍｐｉｒｉｃａｌｃｏｅｆｆｉｃｉｅｎｔ ,ｋｇｓｎ - 2 /ｍＣａｎｄＣ1ＩｎｔｅｇｒａｌｃｏｎｓｔａｎｔＣｔＴｏｔａｌｃｏｍｐｒｅｓｓｉｂｉｌｉｔｙ ,1/ＰａＣρＣｏｍｐｒｅｓｓｉｂｉｌｉｔｙｏｆｆｌｕｉｄ ,1/ＰａＣｒＣｏｍｐｒｅｓｓｉｂｉｌｉｔｙｏｆｒｏｃｋ ,1/ＰａｇＴｈｅｇｒａｖｉｔａｔｉｏｎａｌａｃｃｅｌｅｒａｔｉｏｎ ,ｍ/ｓ2ｈｅｆｆｅｃｔｉｖｅｔｈｉｃｋｎｅｓｓ ,ｍＨＣｏｎｓｉｓｔｅｎｃｙｏｆｐｏｗｅｒ ｌａｗｆ…     

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 LINEAR HOMOGENEOUS FLOW MODEL FOR TWO-PHASE FLOW INSTABILITY IN BOILING CHANNELS

ＮＯＭＥＮＣＬＡＴＵＲＥＤ　ｉｎｎｅｒｄｉａｍｅｔｅｒ (ｍ)Ｑ　ｈｅａｔｆｌｕｘ (ｋｗ/ｍ2 )ｆ　ｆｒｉｃｔｉｏｎａｌｒｅｓｉｓｔａｎｃｅｃｏｅｆｆｉｃｉｅｎｔＴ　ｔｅｍｐｅｒａｔｕｒｅ (°Ｃ)Ｇ　ｍａｓｓｆｌｏｗｖｅｌｏｃｉｔｙ (ｋｇ/ｓ.ｍ2 )ｔ　ｔｉｍｅ (     

A two-scale second-order moment particle turbulence model for gas-particle flow

NOMENCLATURE U — mean velocity u, v — fluctuation velocity uu, vv — Reynolds stress e ― restitution coefficient d ― particle diameter k —kinetic energy α p— particle volume fraction ρ p — particle density β ― drag coefficient ε —kinetic ener     

TWO MODELS FOR ROLL WAVES IN A MUD LAYER

ＴＷＯＭＯＤＥＬＳＦＯＲＲＯＬＬＷＡＶＥＳＩＮＡＭＵＤＬＡＹＥＲＣｈｉａｎｇＣ．Ｍｅｉ；Ｋｏ－ｆｅｉＬｉｕ；Ｃｈｉｕ－ｏｎＮｇ（ＤｅｐａｒｔｍｅｎｔｏｆＣｉｖｉｌａｎｄＥｎｖｉｒｏｎｍｅｎｔａｌＥｎｇｉｎｅｅｒｉｎｇＭａｓｓａｃｈｕｓｅｔｔｓＩｎｓｔ...     

APPLICATION OF A MODIFIED QUICK SCHEME TO DEPTHAVERAGED k-( TURBULENCE MODEL BASED ON UNSTRUCTURED GRIDS

The modified QUICK scheme on unstructured grid was used to improve the advection flux approximation, and the depth-averaged turbulence model with the scheme based on FVM by SIMPLE series algorithm was established and applied to spur-dike flow computation. In this model, the over-relaxed approach was adopted to estimate the diffusion flux in view of its advantages in reducing errors and sustaining numerical stability usually encountered in non-orthogonal meshes. Two spur-dike cases with different defection angles (90oand 135o) were analyzed to validate the model. Computed results show that the predicted velocities and recirculation lengths are in good agreement with the observed data. Moreover, the computations on structured and unstructured grids were compared in terms of the approximately equivalent grid numbers. It can be concluded that the precision with unstructured grids is higher than that with structured grids in spite that the CPU time required is slightly more with unstructured grids. Thus, it is significant to apply the method to numerical simulation of practical hydraulic engineering.     

A MODEL FOR LIQUID SLUG LENGTH DISTRIBUTION IN VERTICAL GAS-LIQUID SLUG FLOW

The slug length and the trailing Taylor bubble velocity in an upward vertical slug flow were measured by using the optical probes and the EKTAPRO 1000 high speed motion analyzer. The correlation between the trailing bubble velocity and the length of liquid slug ahead of that bubble is derived from the experimental data. Based on this correlation as well as the bubble overtaking mechanism, a model for the slug length distribution at any designated locations along the pipe is proposed. The predicted results are in agreement with the experimental data.     

A THREE-SEGMENT HYDRAULIC MODEL FOR ANNULAR CUTTINGS TRANSPORT WITH FOAM IN HORIZONTAL DRILLING

Through mechanical analysis, an improved hydraulic model for annular cuttings transport with foam was established for horizontal drilling. Based on the two critical inclination angles, the entire well was divided into three segments. The Bagnold stress, generalized power law rheological model and modified hindered particle settling velocity in foam fluid were adopted in the model to improve the simulation accuracy. The proposed model allows more precise prediction of cuttings transport property in the whole range of well inclination angle. Model performance was examined via case study and experimental data. Simulation results given by the propulsion iteration and trial-and-error method agree well with in-situ horizontal well drilling practice for the case study, and the comparison between the model prediction and Capo’s experimental data shows satisfactory agreement.     

A TVD SCHEME FOR INCOMPRESSIBLE FLOW COUPLED WITH DIFFERENT TURBULENCE MODLES ON A GROUND- MOUNTED SQUARE-RIB FLOW

A finite-difference Total Variation Diminishing (TVD) numerical simulation model for coupling the Reynolds Averaged Navier-Stokes (RANS) equations, pressure-relative continuity equation and various k-εturbulence models was developed to solve the incompressible flow based on the pseudo-compressibility method. The hyperbolicity of all these equations was studied and the discretization of the fully coupling equations with all the primal variables and source terms were made in this article. Numerical simulation for modeling the flow around a ground-mounted square rib was implemented and validated by comparing with the published wind tunnel experimental data. It is shown that such a numerical simulation method with a proper turbulence model has a very good accuracy to simulate the flow around a surface-mounted rib. It is concluded that the Renormalization Group (RNG) and Chen-Kim k-εturbulence models have much better ability to predict the characteristics of the vortex structure and flow separation than the standard k-εmodel.     

APPLICATION OF A MODIFIED QUICK SCHEME TO DEPTH- AVERAGED κ-ε TURBULENCE MODEL BASED ON UNSTRUCTURED GRIDS

The modified QUICK scheme on unstructured grid was used to improve the advection flux approximation, and the depth-averaged κ-ε turbulence model with the scheme based on FVM by SIMPLE series algorithm was established and applied to spur-dike flow computation. In this model, the over-relaxed approach was adopted to estimate the diffusion flux in view of its advantages in reducing errors and sustaining numerical stability usually encountered in non-orthogonal meshes. Two spur-dike cases with different defection angles （90°and 135°） were analyzed to validate the model. Computed results show that the predicted velocities and recirculation lengths are in good agreement with the observed data. Moreover, the computations on structured and unstructured grids were compared in terms of the approximately equivalent grid numbers. It can be concluded that the precision with unstructured grids is higher than that with structured grids in spite that the CPU time required is slightly more with unstructured grids Thus, it is significant to apply the method to numerical simulation of practical hydraulic engineering.     

ANALYSIS OF WATER QUALITY IN SHALLOW LAKES WITH A TWO-DIMENSIONAL FLOW-SEDIMENT MODEL

The governing equation for sediment pollutions was derived based on the turbulent diffusion of pollutants in shallow lakes. Coupled with shallow water equations, a depth-averaged 2-D flow and water quality model was developed. By means of the conservation law, a proposed differential equation for the change of sediment pollutants was linked to the 2-D equations. Under the framework of the finite volume method, the Osher approximate Riemann solver was employed to solve the equations. An analytical resolution was used to examine the model capabilities. Simulated results matched the exact solutions especially well. As an example, the simulation of CODMn in the Wuli Lake, a part of the Taihu lake, was conducted, which led to reasonable results. This study provides a new approach and a practical tool for the simulation of flow and water quality in shallow lakes.     

A NUMERICAL MODEL OF THE WEIS-FOGH MECHANISM WITH A SEPARATION VORTEX

ＡＮＵＭＥＲＩＣＡＬＭＯＤＥＬＯＦＴＨＥＷＥＩＳ－ＦＯＧＨＭＥＣＨＡＮＩＳＭＷＩＴＨＡＳＥＰＡＲＡＴＩＯＮＶＯＲＴＥＸＺｈａｎｇＳｈｅ－ｓｈｅｎｇ；ＷａｎｇＸｉａｎ－ｆｕ（ＷｕｈａｎＴｒａｎｓｐｏｒｔａｔｉｏｎＵｎｉｖｅｒｓｉｔｙ，Ｗｕｈａｎ４３００...