Population Balanced Model Air Bubble CFD simulation

Description

Population Balanced Model (PBM) Air Bubble CFD simulation, ANSYS Fluent Training

Description

Modeling the breakup and coalescence of air bubbles in a water column using a population balance model is a powerful approach that allows for a more detailed understanding of bubble dynamics and interactions. The population balance model considers the distribution of bubble sizes and tracks their evolution over time, providing insights into the complex processes of breakup and coalescence. By solving the population balance equation, researchers can simulate the behavior of bubbles and predict their evolution in a water column.

Modeling the breakup and coalescence of air bubbles in a water column using a population balance model offers a comprehensive understanding of bubble dynamics. This approach finds applications in wastewater treatment, oil and gas production, chemical engineering, environmental science, and the food and beverage industry. By considering the distribution of bubble sizes and their evolution over time, researchers can optimize processes, improve efficiency, and contribute to advancements in various industrial sectors.

The geometry of the present project was designed using ANSYS design modeler and mesh in ANSYS meshing. The mesh type is structured, and the total element number equals 23,982.

Population Balanced Model Air Bubble Methodology

The Eulerian multiphase model was employed in this simulation to model the two air and water phases and activate the population balance model. This project considered six different classes of bins, with the exponent ratio set to 2. The minimum diameter was also set to 0.00012 m. Aggregation and Breakage kernels were activated, and the Luo model was used for both kernels.

Moreover, the standard k-epsilon model was used to simulate the turbulent flow equations along with considering the mixture method for the turbulence interactions of the phases. Axisymmetric geometry was considered, and since the PBM model is a time-dependent method, a transient study was performed. Furthermore, gravity was also enabled and was set to -9.81 in the X direction.

Conclusion

As shown, different contours, including the phases’ velocity inside the water column, distribution of different classes of bins, along with changes in the fraction of each bin along the axis of the pipe, are shown. In the initial state of the model, bin-3 fraction was set to 1 over the air inlet boundary, and due to the interactions of the water and air phase, coalescence and breakup occur, resulting in the generation of other class bins. These classes’ distribution not only changes as time progresses, but the location over which where we are monitoring them also plays a prominent role in their changes, as shown in the generated plots. Finally, in the histogram plot for the number density, the distribution of each particle diameter based on its number density is shown, which can shed light on the existence frequency of each bin or bubble diameter.

 

This video is the 3rd episode of the Population Balanced Model Training Course