NUMERICAL SIMULATION OF THE TURBULENT FLOW IN ROTATING DUCT

l.INrnODUCT1oNFlowintherotatingductisakindofphenomenonofturbulentflow,whichisoftenfoundintheengineeringapplications,suchasinthecentrifugalcompressor,centrifugalpumpandturbomachinery.Theinvestigationontheductflowisveryimportantfortheen-gineeringpracticejustasthequalityofflowintheductmakesbiginfluenceontheperfor-manceandefficiencyofthemachine.Thestudyontheflowintherotatingductbeganin6os'.JohnsonL1jmeasuredthevelocityofthemainstreaminthetwodimensionalrotatingduct.Comparedwiththeflowinthestati…     

NUMERICAL SIMULATION OF DISCONTINUOUS FLOW IN CIRCULAR CONDUITS

ＮＵＭＥＲＩＣＡＬ　ＳＩＭＵＬＡＴＩＯＮ　ＯＦ　ＤＩＳＣＯＮＴＩＮＵＯＵＳ　ＦＬＯＷ　ＩＮ　ＣＩＲＣＵＬＡＲ　ＣＯＮＤＵＩＴＳＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＤＩＳＣＯＮＴＩＮＵＯＵＳＦＬＯＷＩＮＣＩＲＣＵＬＡＲＣＯＮＤＵＩＴＳ￥ＭａｏＺｅ...     

NUMERICAL MODEL FOR DYNAMIC SIMULATION OF TRAFFIC FLOW

ＮＵＭＥＲＩＣＡＬＭＯＤＥＬＦＯＲＤＹＮＡＭＩＣＳＩＭＵＬＡＴＩＯＮＯＦＴＲＡＦＦＩＣＦＬＯＷＷｕＺｈｅｎｇ；ＺｅｎｇＬｉ－ｎｏｎｇ（ＤｅｐａｒｔｍｅｎｔＡｐｐｌｉｅｄＭｅｃｈａｎｉｃｓ，ＦｕｄａｎＵｎｉｖｅｒｓｉｔｙ，Ｓｈａｇｈａｉ２００４３３，Ｐ...     

废物堆下含水层中流场数值模拟

本文用ＢＥＭ法模拟了废物堆下含水层中的流场，与传统的区域法相比，该法不仅精度高，而且不需进行区域剖分，输入数据和计算工作量少，求解的结果与实测值较吻合。     

NUMERICAL SIMULATION OF BUBBLE FLOW INTERACTIONS

Bubble flow interaction can be important in many practical engineering applications. For instance, cavitation is a problem of interaction between nuclei and local pressure field variations including turbulent oscillations and large scale pressure variations. Various types of behaviours fundamentally depend on the relative sizes of the nuclei and the length scales of the pressure variations as well as the relative importance of bubble natural periods of oscillation and the characteristic time of the field pressure variations. Similarly, bubbles can significantly affect the performance of lifting devices or propulsors. We present here some fundamental numerical studies of bubble dynamics and deformation, then a practical method using a multi-bubble Surface Averaged Pressure (DF-Multi-SAP©) to simulate cavitation inception and scaling, and connect this with more precise 3-D simulations. This same method is then extended to the study of two-way coupling between a viscous compressible flow and a bubble population in the flow field.     

NUMERICAL SIMULATION OF FLOW THROUGH ORIFICE ENERGY-DISSIPATORS IN XIAOLANGDI FLOOD-DISCHAR-GE TUNNEL

1.　INTRODUCTIONThe Xiaolangdi project_ a key water conservancy project on the Yellow River_ isbeing built just now. According to the design scheme. three orifice energy-dissipators willbe installed in each flood-discharge tunnel. It is for the first time that orifice energy-dissipators are used in a large-scale hydraulic engineering.As a kind of internal energy-dissipator,orifices have the following advantages:energy dissipation region is shortand easyto control,and the flow pattern is …     

NUMERICAL SIMULATION OF 3-D FLOW FIELD IN ARCIFORM PLUNGE POOL

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｔｈｅｄｅｓｉｇｎｏｆｐｌｕｎｇｅｐｏｏｌ,ｔｈｅｆｌｏｗｆｉｅｌｄｓｈｏｕｌｄｂｅｕｎｄｅｒｓｔｏｏｄｉｎｄｅｐｔｈ .Ｉｎｆａｃｔ,ｔｈｅｋｎｏｗｌｅｄｇｅｏｎｔｈｅｆｌｏｗｆｉｅｌｄｉｎｐｌｕｎｇｅｐｏｏｌｉｓｔｈｅｂａ     

NUMERICAL SIMULATION OF THE FLOW PATTERNS OF YUQIAO RESERVOIR

In this paper the slot method is used in the computation of 2-dimensional flow withtransient boundary.The slot located inside the computation zone is placed in each space grid,parallel to both X and Y axes.Combined with the operator splitting method,the numerical simu-lation of the flow patterns of Yuqiao Reservior is made.The calculated results are in good agree-ment with observed data.     

NUMERICAL SIMULATION OF TURBULENT FLOW THROUGH THROAT-TYPE ENERGY-DISSIPATORS

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｏｃｏｎｖｅｒｔａｄｉｖｅｒｓｉｏｎｔｕｎｎｅｌｉｎｔｏａｆｌｏｏｄｄｉｓ ｃｈａｒｇｅｔｕｎｎｅｌｃａｎｓａｖｅａｌａｒｇｅａｍｏｕｎｔｏｆｉｎｖｅｓｔｍｅｎｔ.Ｔｈｅｒｅａｒｅｍａｎｙｓｕｃｃｅｓｓｆｕｌｅｘａｍｐｌｅｓｉ     

NUMERICAL SIMULATION OF TRANSIENT FLOW AROUND A SHIP IN UNSTEADY BERTHING MOTION

Ship berthing is a specific maneuver operation. The flow around a berthing ship and the forces acting on the hull are quite different from those for a ship in normal navigation. By solving the unsteady Reynolds-Averaged Navier-Stokes (RANS) equations, the transient flow field around a ship undergoing unsteady lateral motion is simulated and the varying lateral hydrodynamic force acting on the hull is evaluated in this article. The numerical results obtained with different turbulence models are analyzed and compared with experimental results and other numerical results published in literature, and a turbulence model more suitable for simulation of the viscous flow around a ship undergoing unsteady berthing is determined.     

NUMERICAL ANALYSIS OF THE INFLUENCE OF THE TIP CLEARANCE FLOWS ON THE UNSTEADY CAVITATING FLOWS IN A THREE- D IMENSIONAL INDUCER

To clarify the influences of the tip clearance flows on the unsteady cavitating flow,the three-dimensional unsteady cavitating flows through both the two-dimensional cascades and the three-dimensional inducer with and without tip clearance are performed numerically.The governing equations for the compressible fluid flow with the DES turbulence model are employed with the assumption of the isentropic process of liquid phase.The evolution of cavities is represented as the source/sink of vapor phase.The basic equations in the curve linear coordinate are solved by the finite difference method.As the results of the three-dimensional cavitating flows through the two-dimensional cascades,the tip clearance flows from the pressure side to the suction side of the blade produces the tip vortex cavitation,which affects the sheet cavitation on the leading edge of the next blade and enhances the blockage effect near the casing than the flows without tip clearance.On the other hand,in the case of the three-dimensional inducer,the large backflow cavitation is observed around the inlet of the inducer,where the cavities are developed on the casing by the tip clearance flows.The large pressure gradient between the non-cavitating pressure side and the cavitating suction side enhances the tip clearance flows.The calculation considering the tip clearance reproduces the developed cavitation region similar to that of experimental visualizations.Additionally,the backflow cavitation rotates with the speed slower than the rotation speed of the inducer.Then,the rotation of backflow cavitation causes the periodic fluctuation of the outlet pressure greater than that of the inlet pressure.     

NUMERICAL SIMULATION OF GAS-WATER LEAKAGE FLOW IN A TWO LAYERED COALBED SYSTEM

For a two layered coalbed system in possession of the slightly permeable interlayer, a mathematical model was established to describe the methane and water flows between coal seams and the internal migration and the distribution of fluids in a slightly permeable interlayer. Meanwhile, this model has included the potential effect of matrix shrinkage associated with desorption on the coal permeability. The numerical results were obtained by the finite difference method, and then the production forecasts for the two layered coalbed system were conducted in combination with the geological data of a certain area in the Qinshui Basin. Through analyzing the internal migration and distribution of fluids in the slightly permeable interlayer and its effect on the coalbed methane well production, the results indicate that the prediction of the gas production rate and the cumulative gas production will be higher if the permeability of the interlayer is neglected. Furthermore, it is also found that the matrix shrinkage could produce an effect on the coal permeability, thus affecting the production performance.     

NUMERICAL SIMULATION OF FLOW OVER TWO SIDE-BY-SIDE CIRCULAR CYLINDERS

In the present paper, the unsteady, viscous, incompressible and 2-D flow around two side-by-side circular cylinders was simulated using a Cartesian-staggered grid finite volume based method. A great-source term technique was employed to identify the solid bodies (cylinders) located in the flow field and boundary conditions were enforced by applying the ghost-cell technique. Finally, the characteristics of the flow around two side-by-side cylinders were comprehensively obtained through several computational simulations. The computational simulations were performed for different transverse gap ratios (1.5≤T/D≤4) in laminar (Re=100,200) and turbulent (Re=104) regimes, where T and D are the distance between the centers of cylinders and the diameter of cylinders, respectively. The Reynolds number is based on the diameter of cylinders,D. The pressure field and vorticity distributions along with the associated streamlines and the time histories of hydrodynamic forces were also calculated and analyzed for different gap ratios. Generally, different flow patterns were observed as the gap ratio and Reynolds number varied. Accordingly, the hydrodynamic forces showed irregular variations for small gaps while they took a regular pattern at higher spacing ratios.     

NUMERICAL SIMULATION OF NANOPARTICLE COAGULATION IN A POISEUILLE FLOW VIA A MOMENT METHOD

Numerical simulations of coagulating nano-scale aerosols in a two dimensional Poiseuille flow between fixed plates are performed. Evolution of the particle field is obtained by utilizing a moment method to approximate the aerosol general dynamic equation. A moment method is used, which assumes a lognormal function for the particle size distribution and requires knowledge of the first three moments. A Damk？hler number is defined to represent the ratio of the convection time scale to the coagulation time scale. Simulations are performed based on three Reynolds numbers, 100, 500 and 1000, and on three initial particle volume fractions corresponding to Damk？hler numbers 0.1, 0.2 and 1.0. Spatio-temporal evolution of the first three moments along with the geometric mean volume and standard deviation are discussed.     

GRID GENERATION AND NUMERICAL SIMULATION OF 2-D RIVER FLOW

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｎａｔｕｒａｌｒｉｖｅｒ,ｔｈｅｓｈａｐｅｓｏｆｂｏｕｎｄａｒｉｅｓａｎｄｓｅｃ ｔｉｏｎｓａｒｅｏｆｔｅｎｉｒｒｅｇｕｌａｒ ,ｗｈｉｃｈｉｓａｄｉｆｆｉｃｕｌｔｐｒｏｂｌｅｍｆｏｒｎｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎ .Ｔｏｓｏｌｖｅｔｈｉｓｐｒｏｂｌｅｍ ,ａｃｏｏｒｄｉ ｎａｔｅｔｒａｎｓｆｏｒｍａｔｉｏｎｍｅｔｈｏｄｉｓｏｆｔｅｎｕｓｅｄｔｏｔｒａｎｓｆｏｒｍｔｈｅｉｒｒｅｇｕｌａｒｒｅｇｉｏｎｉｎｔｈｅｐｈｙｓｉｃａｌｐｌａｎｅ(Ｘ ,Ｙ)ｔｏｔｈｅｒｅｇｕｌａ…     

NUMERICAL SIMULATION OF TURBULENT FLOW CHARACTERISTICS IN A CURVED PIPE WITH A BAFFLE

A numerical study on the characteristics of developing turbulent flow in a curved pipe with a baffle was carried out in body-fitted coordinates with the k-ε model turbulence. A curved duct of square cross-section was examined first, and the results agree very well with the experimental data. Then two kinds of pipes, a normal curved pipe and that with a baffle were studied. The computational results are presented and compared with each other to illustrate the changes of the flow after adding the baffle. The longitudinal velocity in the pipe with a baffle was characterized by outer velocity bigger than the inner one. The secondary flow was characterized by four-vortex structure with the intensity reduced, which results in the equability of the flow field of the cross-section compared with that without a baffle, and has much more significant meaning in engineering.     

NUMERICAL SIMULATION OF 2-D TIDAL FLOW AND WATER QUALITY UNDER THE CURVILINEAR COORDINATES

This paper presents a numerical method to simulate the 2-D tidal flow and water quality under the curvilinear coordinates. In order to overcome the computational difficulties in natural rivers, such as the complicated boundary figures, the great disparity between length and width of computational domain, etc. , boundary-fitted grid is used, the irregular domain in physical plane is transformed into a rectangular domain in transformed plane, and the depth-averaged momentum equations and mass equation are rewritten and discretized based on the finite volume techniques in curvilinear coordinates. Practical application of the method is illustrated by an example for the Dachangzhen Section of the Yangtze River. A fair agreement between the values measured and computed demonstrates the validity of the method developed.     

NUMERICAL SIMULATION OF A PODDED PROPULSOR IN VISCOUS FLOW

A podded propulsor in viscous flow is numerically simulated in this article.The region of fluid is divided into efficient calculation grids.The pressure and viscous force of blades,pod and strut are obtained as functions of an advance coefficient.The steady result is used as a base in the unsteady simulation to obtain a solution more quickly.The distributions of the thrust and torque fluctuations of the key blade in one revolution are obtained.The calculation results from the mixing plane on steady conditions are compared with those obtained from the sliding mesh model on unsteady conditions.The User-Defined Function(UDF)method is used to simulate the influence of ship hull on the non-uniform wake of the propeller.     

NUMERICAL SIMULATION OF TURBULENT SPOTS IN INCLINED OPEN-CHANNEL FLOW

The generation and evolution of turbulent spots in the open-channel flow are simulated numerically by using the Navier-Stokes equations. An effective numerical method with high accuracy and high resolution is developed.The fourth order time splitting methods with high accuracy is proposed. Thre-dimensional coupling difference methods are presented for the spatial discretization of the Poisson equation of pressure and Hemholtz equations of velocity, therefore, the fourth-order thre-dimensional coupling central difference schemes are constituted. The fourth-order explicit upwind-biased compact difference schemes are designed to overcome the difficulty for the general higher-order central differences cheme which is inadaptable in the boundary neighborhood.The iterative algorithm and overall time marching is used to enhance efficiency. The method is applied in the numerical simulation of turbulent spots at various complex boundary conditions and flow domains. The generation and the developing process of turbulent spots are given, and the basic char acteristics of turbulent spots are shown by simulating the evolution of the wall pulse in inclined open-channel flow.