Euler‐Euler Large Eddy Simulation of a Square Cross‐Sectional Bubble Column Using the Neptune_CFD Code

Abstract

In this work, we report on Euler-Euler large eddy simulation (EELES) of dispersed bubbly flow in a square cross-sectional bubble column. Simulations are performed using the Neptune_CFD package, and results processed using the SALOME platform. The motivation to undertake this study is to check our implementation of the Smagorinsky subgrid-scale (SGS) model into Neptune_CFD. We outline all the physical models used, and we present instantaneous realizations of velocity and void fraction fields in order to illustrate the structure of the turbulence field, and long-time averaged results, to compare with analogous simulations performed using the CFX-4 code and experimental data. The same physical models and constants have been used in both the CFX-4 and Neptune_CFD codes, except the SGS model, which is Smagorinsky in case of Neptune_CFD and a one-equation model in CFX-4. The results obtained with EELES compare reasonably well with experiment, meaning in particular that the implementations have been successful. Some perspectives on the further use of EELES are also given.

Large Eddy Simulation for Dispersed Bubbly Flows: A Review

“…This model incorporates the influence of the gas bubbles in the turbulence by means of additional source terms in the SGS equation and is taken to be proportional to the product of the drag force and the slip velocity between the two phases. This approach was used in work of Niceno et al [10] through the use of a one-equation model. They found significant influence of the additional source terms as used by Pfleger et al [43], as shown in Figure 2.…”

“…[10]. Niceno et al [10] investigated LES with E-E approach for a gas-liquid flow in a square crosssectional bubble column. They demonstrated the applicability of a one-equation model for the SGS kinetic energy ( SGS ).…”

“…This was also found in the work of Van den Hengel et al [31], wherein the authors showed that most of the coalescence occurs in the lower part of the column and recommended to consider bubble size distribution and coalescence and breakup models for reproducing the bubble behaviour near the sparger. [10]. Niceno et al [10] reported LES with E-E approach for a gas-liquid flow in a square crosssectional bubble column.…”

“…[10]. Niceno et al [10] reported LES with E-E approach for a gas-liquid flow in a square crosssectional bubble column. They compared two different codes (CFX-4 and Neptune) and two subgrid-scale models (as in Figure 9).…”

“…It remains to be seen if this was due to the fine mesh used by the authors (Δ/ = 1.2). Niceno et al [10] argued that with the known flow pattern in a bubble column, that is, a dominant bubble plume meandering between the confining walls, the biggest eddy having most energy is of the size of the domain cross section. Thus, the grid used in their work was a compromise between sufficiently fine to capture the most energetic eddies, and sufficiently coarse to stay close to the Milelli criterion [11,24].…”