Bubble Formation and Behaviour Under Hypergravity Conditions

2010 ◽  
Author(s):  
Anna Eiden ◽  
Christina Giannopapa ◽  
Balazs Toth ◽  
Alan Dowson
Keyword(s):  
Water Column ◽  
Bubble Size ◽  
Bubble Dynamics ◽  
Bubble Diameter ◽  
Bubble Formation ◽  
Industrial Applications ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Rates ◽  
Aerospace Applications

Bubble formation and behaviour have been studied over decades, but the complex two-phase flow phenomena involved are still not fully understood. In view of the importance of two-phase flow processes in a broad range of industrial applications, such as the chemical process industry, food industry and aerospace applications, it is crucial to obtain a detailed understanding of single and multiple bubble dynamics. Gravity plays an important role in bubble formation and behaviour. Several studies have been conducted on single bubble formation under microgravity conditions, but the effects of gravitational accelerations much larger than on Earth have not been previously documented. In order to gain a full understanding of the effect of gravity on the bubble dynamics and in view of industrial applications, particularly aerospace applications, it is essential to examine bubble formation and behaviour under hypergravity conditions. Bubble formation and behaviour at the surface of a porous material and at a nozzle were investigated at hypergravity levels of 1–20g using the Large Diameter Centrifuge (LDC) at ESA/ESTEC. The formation of air bubbles through a porous filter into a water column was recorded under hypergravity conditions and the obtained data were analysed qualitatively. A decrease in bubble size and an increase in bubble formation frequency with increasing hypergravity levels could be clearly observed. Data for the experiments on air and oil bubble formation at a nozzle into a water column were recorded under hypergravity conditions using a high speed camera (for different nozzle sizes and air/oil flow rates). For the recorded data from the experiments on air and oil bubble formation at a nozzle, a decrease in bubble size and an increase in bubble formation frequency with increasing gravitational acceleration could be observed qualitatively. Quantitative analysis of the data obtained for the experiments on air bubble formation at a nozzle clearly showed a decrease in average bubble diameter with increasing hypergravity levels. The effect of the nozzle diameter on the bubble size was shown to be small and the bubble diameter was larger for higher flow rates.

Characterisation of Air-Water Two-Phase Flow Using a Wire-Mesh Sensor

2011 ◽  
Author(s):  
Carlos E. F. do Amaral ◽  
O´liver B. S. Scorsim ◽  
Eduardo N. Santos ◽  
Marco Jose´ da Silva ◽  
Marco Germano Conte ◽  
...  
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Industrial Applications ◽  
Wire Mesh ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Rates ◽  
Piping Systems

Two phase flow occurs in many industrial applications, mainly in the transport of mixtures. Many patterns can be produced according to the liquid and gas flow rates. The identification of these patterns is very important in the design of piping systems and equipments. This work proposes an experimental study to identify multiphase flow patterns of water and air in horizontal pipes. The study was developed using an experimental circuit of 26 mm diameter and 9.2 m length pipe, at Thermal Sciences Lab (LACIT) at the Federal University of Technology - Parana´. To characterize the flow patterns, an intrusive mesh electrodes sensor was used, which allows the detailed visualization of the phases distribution. Tests were made using several experimental settings of water and gas flow rates. Measurements were compared to images obtained by high speed camera and the temporal void fraction series which were analyzed with the use of PDF and PSD functions, showing the singularities for each two-phase flow pattern.

Bubble dynamics and oxygen transfer in a hypolimnetic aerator

1998 ◽  
Vol 37 (2) ◽  
pp. 293-300 ◽  
Author(s):  
Vickie L. Burris ◽  
John C. Little
Keyword(s):  
Gas Phase ◽  
Bubble Size ◽  
Oxygen Transfer ◽  
Bubble Dynamics ◽  
Water Flow Rate ◽  
Flow Rates ◽  
Wide Range ◽  
The City ◽  
Close Fit ◽  
Water Supply Reservoirs

A hypolimnetic aerator operating in one of the City of Norfolk's water supply reservoirs was tested. Dissolved oxygen (DO) profiles, water flow rate, and gas-phase holdup were measured over a wide range of applied air flow rates. A model that was developed to predict oxygen transfer in a Speece Cone was modified to conform to the conditions of the hypolimnetic aerator. By varying a single parameter (the initial bubble size) the model was found to provide a close fit to the experimental DO profiles as well as the observed gas-phase holdup. The model was used to show that a doubling in oxygen transfer may be achieved if initial bubble size is reduced from 5 mm to 2.5 mm. Knowing the initial bubble size, it should be possible to predict water velocity by incorporating the effect of momentum. Further work is now underway to test this approach and to examine the possibility of extending this generalized model to cover the range of hypolimnetic aeration and oxygenation devices.

Mixing Characteristics of a Two-Phase Flow (Gas-Liquid) Microchannel Mixer

2011 ◽  
Author(s):  
Tarek Abdel-Salam ◽  
Srikanth Pidugu
Keyword(s):  
Reynolds Number ◽  
Two Phase Flow ◽  
Bubble Formation ◽  
Width Ratio ◽  
Phase Flow ◽  
Two Phase ◽  
Bubble Generation ◽  
Air Bubble ◽  
And Performance ◽  
Actual Shape

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.

Bubble Formation From Porous Plates in Liquid Cross-Flow

2018 ◽  
Author(s):  
Thomas Shepard ◽  
Eric Ruud ◽  
Henry Kinane ◽  
Deify Law ◽  
Kohl Ordahl
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Bubble Diameter ◽  
Bubble Formation ◽  
Cross Flow ◽  
Rectangular Channels ◽  
Gas Liquid Flow ◽  
Liquid Flows ◽  
Processing Techniques ◽  
The Impact

Controlling bubble diameter and bubble size distribution is important for a variety of applications and active fields of research. In this study the formation of bubbles from porous plates in a liquid cross-flow is examined experimentally. By injecting air through porous plates of various media grades (0.2 to 100) into liquid flows in rectangular channels of varying aspect ratio (1–10) and gas/liquid flow rates the impact of the various factors is presented. Image processing techniques were used to measure bubble diameters and capture their formation from the porous plates. Mean bubble diameters ranged from 0.06–1.21 mm. The present work expands upon the work of [1] and further identifies the relative importance of wall shear stress, air injector pore size and gas to liquid mass flow ratio on bubble size and size distribution.

Two-Phase Flow Behavior in Channels With Sudden Area Change Using Experimental and Computational Approach

2017 ◽  
Author(s):  
Ashish Kotwal ◽  
Che-Hao Yang ◽  
Clement Tang
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Experimental Analysis ◽  
Single Phase ◽  
Computational Analysis ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase ◽  
Flow Rates ◽  
Area Change

The current study shows computational and experimental analysis of multiphase flows (gas-liquid two-phase flow) in channels with sudden area change. Four test sections used for sudden contraction and expansion of area in experiments and computational analysis. These are 0.5–0.375, 0.5–0.315, 0.5–0.19, 0.5–0.14, inversely true for expansion channels. Liquid Flow rates ranging from 0.005 kg/s to 0.03 kg/s employed, while gas flow rates ranging from 0.00049 kg/s to 0.029 kg/s implemented. First, single-phase flow consists of only water, and second two-phase Nitrogen-Water mixture flow analyzed experimentally and computationally. For Single-phase flow, two mathematical models used for comparison: the two transport equations k-epsilon turbulence model (K-Epsilon), and the five transport equations Reynolds stress turbulence interaction model (RSM). A Eulerian-Eulerian multiphase approach and the RSM mathematical model developed for two-phase gas-liquid flows based on current experimental data. As area changes, the pressure drop observed, which is directly proportional to the Reynolds number. The computational analysis can show precise prediction and a good agreement with experimental data when area ratio and pressure differences are smaller for laminar and turbulent flows in circular geometries. During two-phase flows, the pressure drop generated shows reasonable dependence on void fraction parameter, regardless of numerical analysis and experimental analysis.

Experimental Determination of Two-Phase Flow Rates of Hydrocarbons Through Restrictions

2006 ◽  
Vol 84 (1) ◽  
pp. 40-53 ◽  
Author(s):  
S.M. Richardson ◽  
G. Saville ◽  
S.A. Fisher ◽  
A.J. Meredith ◽  
M.J. Dix
Keyword(s):  
Experimental Determination ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Rates
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