Conference on Turbulence and Interactions TI2006 May June Porquerolles France

Gretar Tryggvason

Description

1 Conference on Turbulence and Interactions TI2006, May 29 – June 2, 2006, Porquerolles, France Studies of Bubbly Channel Flows by Direct Numerical Simulations Gretar Tryggvason*, Jiacai Lu*, Souvik Biswas*, Asghar Esmaeeli** * Worcester Polytechnic Institute, Worcester, MA, USA ** Southern Illinois University, Carbondale, IL, USA ABSTRACT Recent DNS studies of buoyant bubbly flows in vertical channels are discussed. Simulations of nearly spherical bubbly flows in vertical channels show that the bubbles move towards the wall for upflow and away from the wall for downflow in such a way that the core is in hydrostatic equilibrium. For downflow the wall layer is free of bubbles but for upflow there is an excess of bubbles in the wall layer. The liquid velocity in the core is uniform. For laminar downflow the velocity in the wall layer can be computed analytically and for turbulent flow the velocity is given (almost) by the law of the wall. For upflow the velocity is strongly influenced by the presence of the bubbles. Results from several simulations, fully resolving the flow around each bubble, are used to discuss the effect of void fraction and bubble size for turbulent downflow. INTRODUCTION Bubbly flows in vertical pipes and channels are encountered in a wide variety of industrial systems. The best-known early study of such flows is by Serizawa, Kataoka and Michiyoshi [1,2] who examined experimentally the void fraction distribution and the velocity profile in turbulent air-water bubbly flows.

• both uniform


• laminar bubbly


• flows show


• vertical pipe


• flows


• bubbly flows


• bubble size


• multiphase flow


• bubbles


• wall

Sujets

• Southern Illinois University
• Vertical bar
• Multiphase flow
• Bubbles

Informations

• Publié par: pefav
• Nombre de lectures: 33
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

DNS of Multiphase Flows

Grétar Tryggvason

Jiacai Lu and Souvik Biswas

Worcester Polytechnic Institute

Asghar Esmaeeli

Southern Illinois University

Studies of Bubbly Channel

Flows by Direct Numerical

Simulations

Conference on Turbulence and Interactions TI2006

May 29 – June 2, 2006

DNS of Multiphase Flows

The conservation equations are solved on a regular fixed

grid and the front is tracked by connected marker points

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Conservation of Momentum

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Equation of State:

Singular interface term

Incompressible flow

Computational Approach

DNS of Multiphase Flows

A. Esmaeeli and G. Tryggvason, "An Inverse Energy Cascade

in Two-Dimensional, Low Reynolds Number Bubbly

Flows."

J. Fluid Mech

. 314 (1996), 315-330.

E.A. Ervin and G. Tryggvason, "The Rise of Bubbles in a

Vertical Shear Flow."

ASME J. Fluid Engineering

119

(1997), 443-449.

A. Esmaeeli and G. Tryggvason, "Direct Numerical

Simulations of Bubbly Flows. Part I—Low Reynolds

Number Arrays."

J. Fluid Mech

. 377 (1998), 313-345.

A. Esmaeeli and G. Tryggvason, "Direct Numerical

Simulations of Bubbly Flows. Part II—Moderate

Reynolds Number Arrays"

J. Fluid Mech

. 385 (1999),

325-358.

B. Bunner and G. Tryggvason. Direct Numerical Simulations

of Three-Dimensional Bubbly Flows.

Phys. Fluids

, 11

(1999), 1967-1969.

B. Bunner and G. Tryggvason. Dynamics of Homogeneous

Bubbly Flows: Part 1. Rise Velocity and Microstructure

of the Bubbles.

J. Fluid Mech.

466 (

2002),

17-52.

B. Bunner and G. Tryggvason. Dynamics of Homogeneous

Bubbly Flows. Part 2, Fluctuations of the Bubbles and

the Liquid.

J. Fluid Mech

466 (

2002),

53-84.

B. Bunner and G. Tryggvason. G. Bunner and G. Tryggvason.

“Effect of Bubble Deformation on the Stability and

Properties of Bubbly Flows.”

J. Fluid Mech

. 495 (2003),

77-118

.

Applications of DNS to bubbly flows