Simulations of bubbly two-phase flow in hydraulic jumps of relatively high Reynolds number

Multiphase phase flows occur in many engineering and bio-medical applications. Bubble formation in microchannels can be beneficial or harmful depending upon their influence on the operation and performance of microfludic devices. Potential uses of bubble generation found in many applications such as microreactors, micropump, and micromixers. In the present work the flow and mixing process in a passive microchannel mixer were numerically investigated. Effects of velocity, and inlet width ratio (Dgas/Dliquid) on the two phase flow were studied. Numerical results are obtained for 2-dimensional and 3-dimesional cases with a finite volume CFD code and using structured grids. Different liquid-gas Reynolds number ratios (Reliquid/Regas) were used ranging from 4 to 42. In addition, three values of the inlet width ratio (Dgas/Dliquid) were used. Results for the 3-D cases capture the actual shape of the air bubble with the thin film between the bubble and the walls. Also, increasing Reliquid increases the rate of the development of the air bubble. The bubble length increases with the increase of Dgas/Dliquid. For the same values of Re, the rate of growth of the bubble increases with the increase of Dgas/Dliquid. Finally, a correlation is provided to predict the length of the bubble with liquid-gas Reynolds number ratio (Reliquid/Regas) and tube width.

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Air-Water Two-Phase Flow through a Pipe Junction : Effect of the Reynolds Number on the Local Void Fraction Distribution

JSME international journal Ser 2 Fluids engineering heat transfer power combustion thermophysical properties ◽

10.1299/jsmeb1988.35.1_76 ◽

1992 ◽

Vol 35 (1) ◽

pp. 76-81

Author(s):

Tetsuo SUU

Keyword(s):

Reynolds Number ◽

Void Fraction ◽

Two Phase Flow ◽

Phase Flow ◽

Two Phase ◽

Void Fraction Distribution ◽

Fraction Distribution ◽

Flow Through

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Two-Phase Wakes in Adiabatic Liquid-Gas Flow Around a Cylinder

Volume 2: Fluid Mechanics; Multiphase Flows ◽

10.1115/fedsm2020-20279 ◽

2020 ◽

Author(s):

Dohwan Kim ◽

Matthew J. Rau

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

High Speed ◽

Gas Flow ◽

Two Phase Flow ◽

Water Channel ◽

Phase Flow ◽

Two Phase ◽

Flow Around A Cylinder ◽

High Heat Transfer

Abstract Small tubes and fins have long been used as methods to increase surface area for convective heat transfer in single-phase flow applications. As demands for high heat transfer effectiveness has increased, implementing evaporative phase-change heat transfer in conjunction with small fins, tubes, and surface structures in advanced heat exchanger and heat sink designs has become increasingly attractive. The complex two-phase flow that results from these configurations is poorly understood, particularly in how the gas phase interacts with the flow structure of the wake created by these bluff bodies. An experimental study of liquid-gas bubbly flow around a cylinder was performed to understand these complex flow physics. A 9.5 mm diameter cylinder was installed horizontally within a vertical water channel facility. A high-speed camera captured the movement of the liquid-gas mixture around the cylinder for a range of bubble sizes. Liquid Reynolds number, calculated based on the cylinder diameter, was varied approximately from 100 to 3000. Time-averaged probability of bubble presence was calculated to characterize the cylinder wake and its effects on the bubble motion. The influence of the liquid Reynolds number, superficial air velocity, and bubble size is discussed in the context of the observed two-phase flow patterns.

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Single- and two-phase pressure drop through vertical Venturis

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406220906424 ◽

2020 ◽

Vol 234 (12) ◽

pp. 2349-2359 ◽

Cited By ~ 1

Author(s):

Abdelkader Messilem ◽

Abdelwahid Azzi ◽

Ammar Zeghloul ◽

Faiza Saidj ◽

Hiba Bouyahiaoui ◽

...

Keyword(s):

Pressure Drop ◽

High Reynolds Number ◽

Single Phase ◽

Area Ratio ◽

Superficial Velocity ◽

Phase Flow ◽

Single Phase Flow ◽

Two Phase ◽

High Reynolds ◽

Phase Pressure

An experimental investigation of the pressure drops measurements in a Venturi placed in a vertical pipe is achieved. Venturis with diameter ratios equal to 0.4, 0.55, and 0.75 were employed. Differential pressure transducers were used to measure the pressure drop between the Venturi inlet and the throat sections. The void fraction was measured upstream the Venturi using a conductance probe technique. Air and water superficial velocities ranges were chosen to cover single-phase flow and bubbly, slug, and churn flow regimes. The single-phase pressure drop increases with the liquid superficial velocity. The Venturi pressure drop coefficient increases with decreasing the Venturi area ratio. The discharge coefficient increases slightly with this ratio and approaches a value of unity at high Reynolds number. The two-phase flow pressure drop and the multiplier coefficient increase with the gas superficial velocity and with decreasing the area ratio. Dimensionless pressure drop decreases with increasing the liquid to gas superficial velocity ratio and approaches an asymptotic value at high ratio (greater than 10). This value matches the single-phase flow dimensionless pressure drop value at high Reynolds number. The Venturi with area ratio equal to 0.55 was shown to correlate well the two-phase multiplier and the liquid holdup.

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Quantification of Mixing in RIM Using a Non-Diffusive Two-Phase Flow Numerical Model

International Journal of Chemical Reactor Engineering ◽

10.2202/1542-6580.2564 ◽

2011 ◽

Vol 9 (1) ◽

Cited By ~ 5

Author(s):

Cláudio P. Fonte ◽

Ricardo J. Santos ◽

Madalena M. Dias ◽

José Carlos B. Lopes

Keyword(s):

Fluid Dynamics ◽

Reynolds Number ◽

Two Phase Flow ◽

Phase Flow ◽

Linear Scale ◽

Cfd Simulations ◽

Two Phase ◽

Vof Model ◽

Mixing Chamber ◽

Computational Fluid Dynamics Cfd

Mixing in RIM is made mainly by advective mechanisms, rather than diffusion. In this paper, the advective mechanisms that enable reducing the mixing scales down to the values required for the complete chemical reaction of the two monomers inside the RIM mixing chamber are identified and studied. From Computational Fluid Dynamics (CFD) simulations of non-diffusive two-phase flow using the Volume-of-Fluid (VOF) model, a linear scale of segregation is determined as a measure of the degree of mixing and the effect of the Reynolds number is studied.

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Development of a k-ε Model for Bubbly Two-Phase Flow

Journal of Fluids Engineering ◽

10.1115/1.2910220 ◽

1994 ◽

Vol 116 (1) ◽

pp. 128-134 ◽

Cited By ~ 133

Author(s):

M. Lopez de Bertodano ◽

R. T. Lahey ◽

O. C. Jones

Keyword(s):

Basic Assumption ◽

Single Phase ◽

Two Phase Flow ◽

Phase Flow ◽

Two Phase ◽

Turbulence Suppression ◽

Volume Coefficient ◽

Turbulence Data ◽

High Reynolds ◽

Additional Coefficient

An extension of the k-ε model for bubbly two-phase flow is proposed and tested against experimental data. The basic assumption made is that the shear-induced turbulence and bubble-induced turbulence may be linearly superposed. This assumption results in a model with two time constants that matches both homogeneous two-phase turbulence data (Lance and Bataille, 1991) and pipe data (Serizawa, 1986). The coefficients of the single-phase k-ε model have not been modified and only one additional coefficient is required: the virtual volume coefficient of the bubbles, which may be determined from first principles. This model not only agrees with the data trends, but it also predicts the turbulence suppression which has been measured for high Reynolds number bubbly air/water flows in pipes.

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