Validation of the Diffusion Mixture Model for the simulation of bubbly flows and implementation in OpenFOAM

In this paper we present the implementation and the validation of the Diffusion Mixture Model as a valuable alternative to other popular models for the simulation of gas-liquid systems. The Diffusion Mixture Model treats the gas-liquid system as if it consists of only one phase: the gas-liquid mixture. The difference between the Diffusion Mixture Model and others lies in the minor simplification made during its development, since a more accurate approach for evaluating the interactions between the different phases is considered. The method is implemented and tested in OpenFOAM, by using as test case a rectangular bubble column. This study shows the effectiveness of the Diffusion Mixture Model which turns out to be accurate in the description of both global and local properties. This accuracy comes with a cheaper computational cost as the model solves a smaller number of transport equations, when compared with the two-fluid or the multi-fluid models. Moreover, since this version of the Mixture Models has never been studied in detail, we carried out, during the validation, a thorough analysis on all the simplifications that can be implemented, comparing performance improvements in terms of accuracy and computational costs.