Three-Dimensional Vortex Method for the Simulation of Bubbly Flow

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Tomomi Uchiyama ◽  
Shoji Matsumura
Keyword(s):  
Large Scale ◽  
Bubbly Flow ◽  
Three Dimensional ◽  
Vortex Method ◽  
Bubble Motion ◽  
Bubble Plume ◽  
Vorticity Field ◽  
Buoyant Force ◽  
Hydrogen Bubbles ◽  
Vortex Element

This study proposes a three-dimensional vortex method for the simulation of bubbly flow. The method discretizes the vorticity field by vortex elements. The behavior of the vortex element and the bubble motion are simultaneously analyzed with the Lagrangian approach to compute the time evolution of the flow. This study also applies the vortex method to the simulation of a bubble plume to demonstrate the validity of the method. In a tank containing water, small hydrogen bubbles are released from the bottom of the tank. The bubbles rise due to the buoyant force and induce the water flow around them. The simulation for the plume at the starting period highlights that the rising bubbles induce large-scale eddies at their top and that the bubbles are entrained into the eddies. The simulation for the developed plume demonstrates that large-scale eddies appear around the rising bubbles and that they cause the meandering behavior of the plume. Such three-dimensional features of the bubble plume are favorably compared with the experimental results, indicating the validity of the proposed vortex method.

Numerical simulation of plane bubble plume by vortex method

2008 ◽  
Vol 222 (7) ◽  
pp. 1193-1201 ◽  
Author(s):  
T Uchiyama ◽  
T Degawa
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Vortex Method ◽  
Vortical Flow ◽  
Bubble Plume ◽  
Two Phase ◽  
Buoyant Force ◽  
Hydrogen Bubbles ◽  
Coupling Approach ◽  
Volume Method

This study is dealing with the two-dimensional numerical simulation of a plane bubble plume experimentally investigated by Alam and Arakeri. A vortex method for gas—liquid two-phase flow, proposed by the authors in a prior paper, is applied for the simulation. The method simulates the bubble motion and the induced liquid flow by the two-way coupling approach. In a tank containing water, small hydrogen bubbles are released from an electrode placed on the base of the tank. The bubbles, rising due to the buoyant force, cause the vortical flow of water. The existing numerical methods, such as the finite-difference method and the finite-volume method, compute the bubble plume with regard to the velocity field. But the vortex method calculates directly the vorticity field. Therefore, it promises to simulate successfully the vortical structure predominating the bubble plume. The present simulation makes clear that the meandering behaviour of bubble plume is caused by the large-scale eddies induced by the rising bubbles. The effect of bubble flowrate on the meandering behaviour in the simulation is confirmed to agree well with the experiment. It is also demonstrated that the time-averaged water velocity on the horizontal sections satisfies the similarity distribution when the bubble flowrate is low. These indicate that the authors’ vortex method is indeed applicable to the analysis of plane bubble plume.

scholarly journals Vortex Simulation of the Bubbly Flow around a Hydrofoil

2007 ◽  
Vol 2007 ◽  
pp. 1-9 ◽  
Author(s):  
Tomomi Uchiyama ◽  
Tomohiro Degawa
Keyword(s):  
Volume Fraction ◽  
Bubbly Flow ◽  
Bubble Diameter ◽  
Flow Analysis ◽  
Vortex Method ◽  
Bubble Motion ◽  
Two Phase ◽  
Vortex Element ◽  
Dimensional Simulation ◽  
Free Turbulent Flow

This study is concerned with the two-dimensional simulation for an air-water bubbly flow around a hydrofoil. The vortex method, proposed by the authors for gas-liquid two-phase free turbulent flow in a prior paper, is applied for the simulation. The liquid vorticity field is discrerized by vortex elements, and the behavior of vortex element and the bubble motion are simultaneously computed by the Lagrangian approach. The effect of bubble motion on the liquid flow is taken into account through the change in the strength of vortex element. The bubbly flow around a hydrofoil of NACA4412 with a chord length 100 mm is simulated. The Reynolds number is2.5×105, the bubble diameter is 1 mm, and the volumetric flow ratio of bubble to whole fluid is 0.048. It is confirmed that the simulated distributions of air volume fraction and pressure agree well with the trend of the measurement and that the effect of angle of attack on the flow is favorably analyzed. These demonstrate that the vortex method is applicable to the bubbly flow analysis around a hydrofoil.

Application of a Vortex Method to Fluid Dynamics in Sports Science

2007 ◽  
Author(s):  
Kyoji Kamemoto ◽  
Akira Ojima
Keyword(s):  
Fluid Dynamics ◽  
Three Dimensional ◽  
Vortex Method ◽  
Mathematical Treatment ◽  
Sports Science ◽  
Lagrangian Simulation ◽  
Eddy Simulation ◽  
Flow Features ◽  
Vortex Element ◽  
Basic Equations

This paper describes a pioneering work of practical application of an advanced vortex method in the field of fluid dynamics in sports science. The vortex method developed by the present authors is one of vortex element methods based on the Biot-Savart law, and it is known that the method provides a Lagrangian simulation of unsteady and vortical flows. In this study, in order to examine the applicability of the vortex method, three-dimensional, complex and unsteady flows around an isolated 100 m runner and a ski-jumper were calculated. Basic equations and mathematical treatment of the method are explained in this paper, and calculation conditions and panel data of deforming configuration of the athletes are described. As results of the present study, vortical and unsteady flow features around a runner and a ski-jumper are understood, and unsteady variation of aerodynamic forces corresponding to deformation of body configuration due to athletic motion are calculated. And, it is confirmed that the advanced vortex element method is a promising way to a grid-free Lagrangian large eddy simulation of unsteady and complex flows around dynamic bodies of athletes.

Self Organized Structure of Microbubble Plume in a Thin Fluid Layer

2011 ◽  
Author(s):  
Yoshihito Miyagishima ◽  
Tomoaki Watamura ◽  
Yuji Tasaka ◽  
Yuichi Murai
Keyword(s):  
Liquid Phase ◽  
Large Scale ◽  
Fluid Layer ◽  
Bubbly Flow ◽  
The Self ◽  
Bubbly Flows ◽  
Bubble Plume ◽  
Accumulation Pattern ◽  
Thin Fluid ◽  
Self Organized

This study aims to clarify the self-organized structure of microbubble plume as a result of two-way interaction between microbubbles and a flow of the surrounding liquid medium. We observed a sequence on a development of microbubble plumes in a thin fluid layer. Here the microbubbles show accumulation pattern with a different wavenumber depending on the height in the vessel. Variation of spatial wavenumber in the developing process was determined from visualization images, and three areas were distinguished in this process; (1) the area of rising microbubbles with a large wavenumber in a horizontal direction without time dependence; (2) the area of forming a large-scale flow structure, called ‘microbubble plume’ here, which keeps the primary information, horizontal wavenumber of the bubble accumulation with a large wavenumber; (3) the area where the microbubble distribution takes a smaller wavenumber and makes vertical accumulation pattern inside the bubbly flow that is due to the mutual interaction between rising microbubbles and a flow induced by bubbles. To clarify these mutual interactions between liquid and gas phases, we visualized fluid motion of the liquid phase around the microbubble plumes by laser induced fluorescence, LIF. In this way, swaying motions on the tip of rising up bubble plume and liquid phase entrainment into the bubble plumes were visualized. We found the mechanisms for the creation of the self-organized distribution of microbubbles in bubbly flows and its temporal change as the result of the interaction between gas and liquid phase motions in bubbly flows.

Numerical Simulation of a Compound Round Jet by Three-Dimensional Vortex Method

2003 ◽  
Author(s):  
Tomomi Uchiyama
Keyword(s):  
Reynolds Shear Stress ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Vortex Method ◽  
The Self ◽  
Experimental Result ◽  
Axial Component ◽  
The Core ◽  
Maximum Value ◽  
Vortex Element

A jet issuing with velocity U0 from a round nozzle of diameter D into the same fluid co-flowing with velocity Ua is simulated by the three-dimensional vortex method. The velocity ratio Ua/U0 is 0.27, while the Reynolds number based on U0 and D is 5.5×104. The number of vortex elements drastically increases in the region where the stretch and contraction of the vortex element occur due to the appearance of turbulence. When applying the core distribution function proposed by Winkelmans and Leonard, the time-averaged velocity successfully satisfies the self-preservation distribution, and the axial component of the turbulent intensity almost agrees with the experimental result. The Reynolds shear stress takes its maximum value at the periphery of the jet in accordance with the experimental result, though it is higher than the experiment.

Numerical Study of the Three-Dimensional Structure of a Bubble Plume

2000 ◽  
Vol 122 (4) ◽  
pp. 754-760 ◽  
Author(s):  
Y. Murai ◽  
Y. Matsumoto
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Lagrangian Model ◽  
Dimensional Structure ◽  
Bubble Motion ◽  
Bubble Plume ◽  
Two Phase ◽  
Simulated Flow ◽  
Good Agreement

The whole behavior and the micro scale flow characteristics of a three-dimensional bubble plume are investigated numerically. The bubble plume drives liquid convection in a tank due to strong local two-phase interaction so that the Eulerian-Lagrangian model is formulated with emphasis on the translational motions of the bubble. In this model, each bubble motion is tracked in a bubbly mixture which is treated as a continuum. The three-dimensional numerical results reveal several particular structures, such as swaying and swirling structures of the bubble plume. These simulated flow structures show qualitatively good agreement with the experimental observations. Furthermore, the detailed behavior in the bubble plume is clarified by various analysis to discuss the dominant factors causing such the strong three-dimensionality. [S0098-2202(00)00904-4]

Analysis of Unsteady Flow Around Airfoil of a HAWT by Vortex Method

2003 ◽  
Author(s):  
Hiroshi Imamura ◽  
Daisuke Takezaki ◽  
Masahiro Kawai ◽  
Yutaka Hasegawa ◽  
Koji Kikuyama
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Deterministic Model ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Simple Algorithm ◽  
Vortex Method ◽  
Vortex Methods ◽  
Outer Flow ◽  
Vortex Element

Vortex methods have features such as relatively simple algorithm, no grid-generation in flow field and lagrangian scheme which traces each vortex element concentrated in a tiny region. It is considered that the vortex methods are effective tools for the analysis of three-dimensional, incompressible and unsteady outer flow such as flow around wind turbines. Recently, vortex methods are employed as engineering tools for three-dimensional unsteady flow. In a flow simulation by vortex methods, accuracy of simulation depends chiefly on the vortex creation model on the wall and the viscous diffusion effects. However, it seems that the deterministic model to introduce the vortex element created on the wall into flow field has not yet been accomplished. In this paper, an introduction model of vortex elements from the wall into flow field is proposed. This model is based on the analogy of the consideration of boundary-layer. In this model, intensity of vortex elements created on the wall is determined by applying both no-through and no-slip boundary conditions and the diffusion height of each element created on the wall is determined dynamically. To investigate the applicability of the model, proposed method is applied to flow around impulsively started airfoil section.

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