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 ON VELOCITIES OF TWO INTERACTING FIBERS IN FIBER SUSPENSION

1 .　INTRODUCTIONFibersuspensions,widelyusedinmaterial,chemicalandtestileindustry ,areinvolvedwithmanydifficultiesrelatedtomultiphaseflowandnon newtonianfluidmechanics .Infibersuspen sions ,thefibersinteractwiththefluid .Theexist enceandmotionofthefibersaffectthepropertiesofthefluid greatly ;ontheotherhand ,itisthefluidthatdeterminesthefibers’translationalandrotationalmotion .Thusfibersuspensionformsacomplexdynamicalsystem .Infibersuspension ,thefibersalsointeractwitheachother .Generall…     

COMPUTATION OF HYDRODYNAMIC INTERACTION FORCES BETWEEN SHIPS BASED ON B-SPLINES

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＷｉｔｈｉｎｔｈｅａｓｓｕｍｐｔｉｏｎｏｆｓｌｅｎｄｅｒ ｔｈｅｏｒｙ ,Ｙｅ ｕｎｇ[1 ,2 ] ｆｉｒｓｔｒｅｃａｓｔｔｈｅｔｈｒｅｅ ｄｉｍｅｎｓｉｏｎａｌｐｒｏｂｌｅｍｏｆｔｗｏｓｈｉｐｓｍｏｖｉｎｇｉｎａｓｈａｌｌｏｗｆｌｕｉｄｉｎｔｏｔｗｏｉｎｎｅｒｐｒｏｂｌｅｍｓａｎｄｏｎｅｏｕｔｅｒｐｒｏｂｌｅｍａｎｄｄｅｒｉｖｅｄａｐａｉｒｏｆｃｏｕｐｌｅｄｉｎｔｅｇｒａｌ ｄｉｆｆｅｒｅｎｔｉａｌｅｑｕａｔｉｏｎｓｆｏｒｄｅｔｅｒｍｉｎｉｎｇｔｈｅｕｎｋｎｏｗｎｃｒｏｓｓ ｆ…     

NUMERICAL INVESTIGATION ON FLOW CHARACTERISTICS IN RIBBED BEND

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｇａｓ ｐａｒｔｉｃｌｅｆｌｏｗｉｎｃｕｒｖｅｄｄｕｃｔｓｈａｖｅｂｅｅｎｗｉｄｅｌｙａｐｐｌｉｅｄｉｎｅｎｇｉｎｅｅｒｉｎｇ .Ｒｅｓｅａｒｃｈ[2 ] ｓｈｏｗｓｔｈａｔｔｈｅｅｒｏｓｉｏｎｅｆｆｉｃｉｅｎｃｙｏｆｂｅｎｄｉｓ 5 0ｔｉｍｅｓｈｉｇｈｅｒｔｈａｎｔｈａｔｏｆｓｔｒａｉｇｈｔｐｉｐｅ .Ｔｈｅｒｅｆｏｒｅ ,ｉｍｐｒｏｖｉｎｇｔｈｅａｂｉｌｉｔｙｏｆｂｅｎｄｅｒｏｓｉｏｎｐｒｏｔｅｃｔｉｏｎｉｓａｎｕｒｇｅｎｔｔａｓｋ .Ｔｈｅｐｒｅｖｉｏｕｓｒｅｓｅａｒｃ…     

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 SOLUTION FOR TIDAL FLOW IN OPENING CHANNEL USING COMBINED MACCORMACK-FINITE ANALYSIS METHOD

A new numerical scheme for solving the tidal flow in an opening channel using the advective-diffusion shallow-water equations as the governing equations is proposed based on the combination of the MacCormack and the finite analysis methods. In the present scheme, the finite analysis method is used to discretize the momentum equation and the MacCormack technique is used to discretize the continuity equation in a single grid system. The matrix of the discretized momentum equation is characterized by predominantly main diagonal elements, which ensures favorable convergence and stability for the numerical simulation by the combined method. To verify the present method, hydraulics simulation is carried out for a section down mainstream of the Huangpu River. The computational results agree with the measured data. By use of orthogonal curvilinear coordinate system, the methods can be easily extended to the numerical simulation of the tidal flow in a tortuous channel.     

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.     

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.     

NUMERICAL SIMULATION ON 2-D WATER-AIR TWO-PHASE FLOW OVER TOP OUTLET

Flood discharge over top outlet of dam is simu-lated by 2-dimension water-air two-phase mathematical model.Distribution of dynamic pressure, turbulent kinetic energy (k), turbulent dissipation rate (ε) , free water surface and veloci-ty field have been obtained. The simulated results were testedby physical model, which shows that the computed results areidentical with that of the physical model.     

NUMERICAL STUDY ON THE VORTEX STRUCTURES IN THE WAKE OF AN OSCILLATING CIRCULAR CYLINDER IN A UNIFORM FLOW

ＮＵＭＥＲＩＣＡＬＳＴＵＤＹＯＮＴＨＥＶＯＲＴＥＸＳＴＲＵＣＴＵＲＥＳＩＮＴＨＥＷＡＫＥＯＦＡＮＯＳＣＩＬＬＡＴＩＮＧＣＩＲＣＵＬＡＲＣＹＬＩＮＤＥＲＩＮＡＵＮＩＦＯＲＭＦＬＯＷＬｕＸｉ－ｙｕｎ；ＴｏｎｇＢｉｎｇ－ｇａｎｇ；ＺｈｕａｎｇＬｉ－ｘｉａｎ...     

NUMERICAL SIMULATION OF ATOMIZATION RAINFALL AND THE GENERATED FLOW ON A SLOPE

This article studies the atomization rainfall and the generated flow on a slope by numerical simulations.The atomization rainfall is simulated by a unified model for splash droplets and a suspended mist,and the distribution of the diameter of splash rain drops is analyzed.The slope runoff generated by the atomization rainfall is simulated by a depth-averaged 2-D model,and the localization of the rainfall intensity in space is specially considered.The simulation results show that:(1) the median rain size of the atomization rainfall increases in the longitudinal direction at first,then monotonously decreases,and the maximum value is taken at the longitudinal position not in consistent with the position where the maximum rain intensity is taken.In the lateral direction the median rain size monotonously decreases,(2) since the atomization rainfall is distributed in a strongly localized area,it takes a longer time for its runoff yield to reach a steady state than that in the natural rainfall,the variation ranges of the water depth and the velocity in the longitudinal and lateral directions are larger than those in the natural rainfall.     

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 EFFECT OF FILLET FORMS ON APPENDAGE－BODY JUNCTION FLOW

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＴＨＥＥＦＦＥＣＴＯＦＦＩＬＬＥＴＦＯＲＭＳＯＮＡＰＰＥＮＤＡＧＥ－ＢＯＤＹＪＵＮＣＴＩＯＮＦＬＯＷＬｉＤｉｎｇ；ＺｈｏｕＬｉａｎ－ｄｉ（ＣｈｉｎａＳｈｉｐＳｃｉｅｎｔｉｆｉｃＲｅｓｅａｒｃｈＣｅｎｔｅｒＰ．...     

NUMERICAL SIMULATION FOR SHALLOW FLOW AND POLLUTANT DISPERSION BASED ON QUAD-TREE MESHES

1. INTRDUCTION Natural flow domains have complicated boundary configurations, which may themselves strongly influence the interior flow patterns.Sometimes, high-gradient zones and local areas which are relatively important in some problems are included in…     

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 STUDY ON QUASI- STEADY FLOW OF NONNEWTONIAN FLUID IN SUCK-ROD PUMP

This paper presents a numerical method for simulation of the flow and thecalculated results of the quasi-steady axisymmetrical flow field and pressure distribution on valveball with power-law model for Non-Newtonian fluid in suck-rod pump.We believe the methodcan provide a foundation for further research and improvement of the design of suck-rod pump.     

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.