Modeling and Simulation of Turbulent Bubbly Flows


Modeling and Simulation of Turbulent Bubbly Flows

Parekh, J.

The application of multiphase computational fluid dynamics (CFD) simulation for scale-up and intensification of chemical engineering processes bears the potential to identify energy- and resource- efficient solutions. This avoids the need to employ the conventional semi-empirical methods which are expensive and time-consuming.
Such simulations are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, for practical applications, suitable closure relations are needed which describe the physics on the scale of individual bubbles or groups thereof. A suitable closure model for the fluid dynamics of bubbly flows is developed at HZDR. The goal of this development is to establish a predictive model which is validated for a broad range of applications. For this purpose, simulations results are compared with experimental data.
Within the present project, a full Reynolds-stress turbulence model is introduced into the mathematical framework and compared with the two-equation model used so far. In particular, new anisotropic source terms for the bubble-induced turbulence are investigated. Bubbly pipe flows, in which individual components of the Reynolds-stress tensor have been measured, are considered as applications. The simulations are run in OpenFOAM.
Simulation results for the gas fraction, liquid velocity and turbulent kinetic energy are largely found to be in accordance with the experimental measurements. Deviations occur mostly for some cases with larger superficial gas velocity. Reynolds-stress models (RSMs) when extended to include the bubble-induced turbulence demonstrate the potential to predict the Reynolds stresses. The RSMs thereby are able to account for the deficiencies of the two-equation turbulence model.

Keywords: dispersed gas liquid multiphase flow; Euler-Euler two-fluid model; Reynolds stress turbulence model; bubble-induced turbulence; CFD simulation; model validation

  • Master thesis
    RWTH Aachen, 2017
    Mentor: Prof. Dr.-Ing. Heinz Pitsch

Permalink: https://www.hzdr.de/publications/Publ-25450
Publ.-Id: 25450