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 OF GAS TURBULENCE ENHANCEMENT BY PARTICLE-WAKE EFFECT

A new turbulence enhancement model was incorporated into the second-order moment two-phase turbulence model and was used to simulate gas-particle flows in swirling chambers and channels with different wall roughness. The results show that compared with the turbulence modification model not accounting for the wake effect,this model,together with the conventional particle source term,gives simulation results in better agreement with the experimental data.     

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.     

2-ORDER TURBULENCE CLOSURE PLANKTON ECOSYSTEM DYNAMICS MODEL AND ITS APPLICATION

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＯｎｃｅ ｐｅｏｐｌｅｂｒｏｋｅｔｈｒｏｕｇｈｔｈｅｌｉｍｉｔａｔｉｏｎｏｆｔｒａｄｉｔｉｏｎａｌｅｃｏｌｏｇｙｔｏｓｔｕｄｙｏｎｔｈｅｓｔａｔｉｃｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎｂｉｏｌｏｇｙａｎｄｉｔｓｅｎｖｉｒｏｎｍｅｎｔａｎｄｃａｍｅａｂｏｕｔｔｏｓｔｕｄｙｔｈｅｍｅｃｈａｎｉｓｍｏｆｔｈｅｉｒｉｎｔｅｒａｃｔｉｏｎｉｎｖｉｅｗｏｆｂｉｏｃｈｅｍｉｓｔｒｙａｎｄｅｎｖｉｒｏｎｍｅｎｔｄｙｎａｍｉｃｓ,ｅｃｏｓｙｓ ｔｅｍｄｙｎａｍｉｃｓｇａｉｎｅｄｗｉｄｅ…     

A NEW METHOD FOR SOLVING TURBULENT VELOCITY CORRELATION FUNCTIONS AND ITS APPLICATION TO THE CHANNEL FLOW

ＡＮＥＷＭＥＴＨＯＤＦＯＲＳＯＬＶＩＮＧＴＵＲＢＵＬＥＮＴＶＥＬＯＣＩＴＹＣＯＲＲＥＬＡＴＩＯＮＦＵＮＣＴＩＯＮＳＡＮＤＩＴＳＡＰＰＬＩＣＡＴＩＯＮＴＯＴＨＥＣＨＡＮＮＥＬＦＬＯＷＬｉｎＪｉａｎ－ｚｈｏｎｇ；ＷａｎｇＹｕ－ｚｈｉ（Ｄｅｐａｒｔｍｅｎｔ...     

THE TURBULENT MODEL OF LIQUID-PARTICLE FLOWS AND ITS APPLICATION TO NUMERICAL PREDICTION OF OIL POLLUTION

Simulation of particle turbulent transport in present mathematical models of two-phase turbulent flows is algebraic model based on local following theory. The predicted results bythese models are not consistent with that of experiments available. The motion of two-phase flowis described by a unified model of multi-fluid in this paper. The two-fluid turbulent model oftwo-phase flow based on k-e equations for particles and fluid, and corresponding numerical thch-nique are both developed. The proposed model and the numerical technique are successfully em-ployed to numerical modelling for oil-water two-phase turbulent recirculating flow.     

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.     

STUDIES OF SOLID－LIQUID TWO－PHASE TURBULENT FLOWS AND WEAR IN HYDRAULIC TURBOMACHINERY

ＳＴＵＤＩＥＳＯＦＳＯＬＩＤ－ＬＩＱＵＩＤＴＷＯ－ＰＨＡＳＥＴＵＲＢＵＬＥＮＴＦＬＯＷＳＡＮＤＷＥＡＲＩＮＨＹＤＲＡＵＬＩＣＴＵＲＢＯＭＡＣＨＩＮＥＲＹ￥ＬｉｕＸｉａｏ－ｂｉｎｇ（ＳｉｃｈｕａｎＩｎｓｔｉｔｕｔｅｏｆＴｅｃｈｎｏｌｏｇｙ，Ｃｈｅｎｇｄ...     

A MULTIGRID-ACCELERATED THREE-DIMENSIONAL TRANSIENT-FLOW CODE AND ITS APPLICATION TO A NEW TEST PROBLEM

A multigrid-assisted solver for the three-dimensional time-dependent incompressible Navier-Stokes equations on graded Cartesian meshes is developed. The spatial accuracy is third-order for the convective terms and fourth-order for the viscous terms, and a fractional-step strategy ensures second-order time accuracy. To achieve good time-wise efficiency a multigrid technique is used to solve the highly time-consuming pressure-Poisson equation that requires to be solved at every time step. The speed-up achieved by multigrid is shown in tabular form. The performance and accuracy of the code are first ascertained by computing the flow in a single-sided lid-driven cubic cavity with good grid-economy and comparing the results available in the literature. The code, thus validated, is then applied to a new test problem we propose and various transient and asymptotically obtained steady-state results are presented. Given the care taken to establish the credibility of the code and the good spatio-temporal accuracy of the discretization, these results are accurate and may be used for ascertaining the performance of any computational algorithm applied to this test problem.     

A NEW DEPTH-AVERAGED ALGEBRAIC STRESS MODEL AND ITS VERIFICATION TEST

1.mThonvrmNTurbulencemodelshavefoundtheirwideapplicationsinscienceandtechnolOgyrelaedtofiuidflOw.UptonowvariouskindsOfturbulencemedelsaredeveloPedincludingtheone-equatbomodel(Bradshaw,P.etal.,1967),thetwo-equatbomedel(SPalding,l969),themuliple-equationmodel(Davidov,1961),thealgebraicstressmodl(Launder,etal.,1972)andsoon.Amongthesemodels,thetwo-equationkBmodeliswidelytestedandued.Thealgebraicstressmodelsareintermediatebetweensecond-ordercforuerschemesusingtranSPOrtequatbosfortheindividual…     

NUMERICAL SIMULATION FOR THE STEPPED SPILLWAY OVERFLOW WITH TURBULENCE MODEL

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

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.     

THREE-DIMENSIONAL TURBULENCE NUMERICAL SIMULATION OF A STEPPED SPILLWAY OVERFLOW

In this paper, the κ-ε two-equation turbulence model was used to simulate the three-dimensional turbulent flow of the stepped spillway at the Yubeishan reservoir. In order to solve the curved free water surface and to handle the complex boundary conditions, the fractional Volume Of Fluid (VOF) model that is applicable to the solution of the stratified two-phase flow was intorduced to the κ-ε turbulence model and the unstructured grid was used for the discretization of the irregular simulation domain. By these methods, the turbulent flow field of the stepped spillway was simulated successfully.The location of the free surface along the spillway, the magnitude and distribution of the velocity, the pressure distribution on the step surface, the turbulence kinetic energy and turbulence dissipation rate were obtained by simulation. The changes and distributions of these characteristics along the width of the spillway were also obtained. The energy dissipation ratio of the stepped spillway was calculated according to the upstream and downstream water depth and velocities.     

THREE-DIMENSIONAL TURBULENCE NUMERICAL SIMULATION OF A STEPPED SPILLWAY OVERFLOW

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅａｐｐｌｉｃａｔｉｏｎｏｆｔｈｅｓｔｅｐｐｅｄｓｐｉｌｌｗａｙｈａｓｈａｄａｌｏｎｇｈｉｓｔｏｒｙ .Ｔｈｅ ｐｈｙｓｉｃａｌｍｏｄｅｌｔｅｓｔｓｔｕｄｙｏｆｔｈｅｓｔｅｐｐｅｄｓｐｉｌｌｗａｙｈａｓｂｅｅｎ ｐｅｒｆｏｒｍ     

SIMPLIFIED MODEL AND ITS APPLICATION FOR WAVEMAKING INDUCED BY EXPLOSION

ＳＩＭＰＬＩＦＩＥＤＭＯＤＥＬＡＮＤＩＴＳＡＰＰＬＩＣＡＴＩＯＮＦＯＲＷＡＶＥＭＡＫＩＮＧＩＮＤＵＣＥＤＢＹＥＸＰＬＯＳＩＯＮ￥ＳｈｅｎＧｕｏ－ｇｕａｎｇ；ＬｉＤｅ－ｊｕｎ（ＴａｉｎｊｉｎＵｎｉｖｅｒｓｉｔｙ，Ｔｉａｎｊｉｎ３０００７２，Ｐ．Ｒ．Ｃｈ...     

A TURBULENCE MODEL FOR VARYING DENSITY FLOW IN GENERAL CURVILINEAR COORDINATES

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

基于开关控制策略的厂内经济运行模型及应用

通过划分机组的约束限制条件为安全运行区和非安全运行区，提出了一 种基于开关控制策略的厂内经济运行模型。该模型有效地反映了机组的运行状态，并且保证 了设备的可利用率，较好地解决了影响水轮机效率、使用寿命、甚至可能危及电站运行安全 的机组不可运行区等约束限制问题。算例表明，该方法是有效的。     

STUDY AND APPLICATION OF STEADY FLOW AND UNSTEADY FLOW MATHEMATICAL MODEL FOR CHANNEL NETWORKS

Based on the Preissmann implicit scheme for the one-dimensional Saint-Venant equation, the mathematical model for one-dimensional river networks and canal networks was developed and the key issues on the model were expatiated particularly in this article. This model applies the method of three-steps solution for channel-junction-channel to simulate the river networks, and the Gauss elimination method was used to calculate the sparse matrix. This model was applied to simulate the tree-type irrigation canal networks, complex looped channel networks and the Lower Columbia Slough networks. The results of water level and discharge agree with the data from the Adlul and field data. The model is proved to be robust for simulating unsteady flows in river networks with various degrees of complex structure. The calculated results show that this model is useful for engineering applications in complicated river networks. Future research was recommended to focus on setting up ecological numerical model of water quality in river networks and canal networks.     

NUMERICAL SIMULATION OF MOVING SCOUR BOUNDARY AND TURBULENCE FLOW AROUND SUBMARINE PIPELINES

A two dimensional vertical mathematical model is proposed in this paper for simulating the equilibrium profile of local scour around submarine pipelines. The current model is composed of a new k-ε turbulence model, fitting moving boundary with pre-meshed grid lines and incipient criterion of shear stress for sediments. Employing the proposed model, an instance is carried out numerically and compared with experiments. The calculation results agree well with the experiments. It shows that the improved two equation turbulence model, adopted in this paper is appropriate to simulating the turbulent flow ficld around submarine pipelines, fitting moving boundary with pre-mcshed grid lines method is efficient for moving boundary problems in a multiply connected domain and the stability evaluation method for seabed with critical shear stress based on log-wall law is a reliable choice.     

GEOMORPHIC RESPONSES TO CHANGES IN INSTREAM FLOWS: THE FLOW‐CHANNEL FITNESS MODEL

The flow‐channel fitness model is a conceptual and practical model for predicting the qualitative response of alluvial channels to modifications of flow regimes. ‘Fitness’ refers to the size of channels compared with the flows they convey, with the terminology derived from traditional geomorphic concepts of overfit and underfit streams. The qualitative predictions refer to whether channels experience aggradation, degradation or relative stability, and whether aggradation or degradation is dominated by width or depth. The model is based on transitions among seven possible fitness states, triggered by key thresholds of sediment supply versus transport capacity and shear stress versus shear strength, and requires that potential changes in sediment supply and water surface or energy‐grade slope also be accounted for. The fitness approach can be used where only relative values and changes are known, as is illustrated in three example applications from Texas. The flow‐channel fitness model synthesizes key elements from several existing approaches to predicting geomorphic responses to changes in flow and is intended to augment rather than replace quantitative approaches, providing a predictive tool where the data requirements and assumptions for quantitative models cannot be fully met. Copyright © 2012 John Wiley & Sons, Ltd.