[Numerical and physical modelling of bubbly flow phenomena]

Purpose The purpose of this study is to design numerical simulations of bubbly flow around a cylinder to better understand the characteristics of flow around a rigid obstacle. Design/methodology/approach The bubbly flow around a circular cylinder was numerically simulated using a semi-Lagrangian–Lagrangian method composed of a vortex-in-cell method for the liquid phase and a Lagrangian description of the gas phase. Additionally, a penalization method was applied to account for the cylinder inside the flow. The slip condition of the bubbles on the cylinder’s surface was enforced, and the outflow conditions were applied to the liquid flow at the far field. Findings The simulation clarified the characteristics of a bubbly flow around a circular cylinder. The bubbles were shown to move around and separate from both sides of the cylinder, because of entrainment by the liquid shear layers. Once the bubbly flow fully developed, the bubbles distributed into groups and were dispersed downstream of the cylinder. A three-dimensional vortex structure of various scales was also shown to form downstream, whereas a quasi-stable two-dimensional vortex structure was observed upstream. Overall, the proposed method captured the characteristics of a bubbly flow around a cylinder well. Originality/value A semi-Lagrangian–Lagrangian approach was applied to simulate a bubbly flow around a circular cylinder. The simulations provided the detail features of these flow phenomena.

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Numerical Investigation of Vertical Plunging Jet Using a Hybrid Multifluid–VOF Multiphase CFD Solver

International Journal of Chemical Engineering ◽

10.1155/2015/925639 ◽

2015 ◽

Vol 2015 ◽

pp. 1-14 ◽

Cited By ~ 16

Author(s):

Olabanji Y. Shonibare ◽

Kent E. Wardle

Keyword(s):

Bubble Size ◽

Bubbly Flow ◽

Jet Impingement ◽

Quantitative Prediction ◽

Bubble Plume ◽

Flow Solver ◽

Dynamic Switching ◽

Segregated Flow ◽

Flow Phenomena ◽

Long Time

A novel hybrid multiphase flow solver has been used to conduct simulations of a vertical plunging liquid jet. This solver combines a multifluid methodology with selective interface sharpening to enable simulation of both the initial jet impingement and the long-time entrained bubble plume phenomena. Models are implemented for variable bubble size capturing and dynamic switching of interface sharpened regions to capture transitions between the initially fully segregated flow types into the dispersed bubbly flow regime. It was found that the solver was able to capture the salient features of the flow phenomena under study and areas for quantitative improvement have been explored and identified. In particular, a population balance approach is employed and detailed calibration of the underlying models with experimental data is required to enable quantitative prediction of bubble size and distribution to capture the transition between segregated and dispersed flow types with greater fidelity.

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Physical and Numerical Modelling on the Mixing Condition in a 50 t Ladle

Metals ◽

10.3390/met9111136 ◽

2019 ◽

Vol 9 (11) ◽

pp. 1136

Author(s):

Liu ◽

Bai ◽

Liu ◽

Jönsson ◽

Gan

Keyword(s):

Mathematical Modelling ◽

Flow Pattern ◽

Flow Rate ◽

Gas Flow ◽

Transport Model ◽

Mixing Time ◽

Bubbly Flow ◽

Physical Modelling ◽

Mixing Conditions ◽

Mixing Condition

The bubbly flow and mixing conditions for gas stirring in a 50t ladle were investigated by using physical modelling and mathematical modelling. In the physical modelling, the effect of the porous plugs’ configurations on the tracer homogenization was studied by using a saturated NaCl solution to predict the mixing time and a color dye to show the mixing pattern. In the mathematical modelling, the Euler–Lagrange model and species transport model were used to predict the flow pattern and tracer homogenization, respectively. The results show that, for a ±5% homogenization degree, the mixing time with dual plugs using a radial angle of 180° is shortest. In addition, the mixing time using a radial angle of 135° decreases the most with an increased flow rate. The flow pattern and mixing conditions predicted by mathematical modelling agree well with the result of the physical modelling. For a ±1% homogenization degree, the influence of the tracer’s natural convection on its homogenization pattern cannot be neglected. This is especially true for a ‘soft bubbling’ case using a low gas flow rate. Overall, it is recommended that large radial angles in the range of 135°~180° are chosen for gas stirring in the present study when using dual porous plugs.

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