An LES-Like Multiscale Multiphase Flow Model Based on Break-up and Coalescence Phenomena

The multiscale multiphase flow contains both small-scale (dispersed phase) and large-scale (continuous phase) structures. Standard interface-averaging multiphase models are appropriate for the simulation of flows including small-scale structures. Standard interface-resolving multiphase models are commonly used for the simulation of flow regimes containing large-scale structures. The accurate simulation of different regimes has a crucial role to investigate the physics of multiphase flows. To cover the inability of standard models to simulate multiscale multiphase flows, various generalized hybrid models have been developed. The present research aims to present an LES-like approach to identify the large-scale structures by comparing the equivalent diameter of structures and the averaging length scale. The main difference between the presented model and the models available in the literature is the independency of the model to the thresholds of the local volume fraction to recognize the flow regime. The switching criterion is set based on the cell size and the physical phenomena including the break-up and coalescence mechanisms. To assess the capabilities of the presented multiscale model, four different benchmark cases including the bubble column, the impinging jet, the dam break, and the Rayleigh-Taylor instability are investigated. The physical behavior of the flow is considered as a reference and compared with numerical results. It is demonstrated that the present multifluid model is capable to capture the physical characteristics of both dispersed and segregated flow regimes, and it is a forward step to develop a generalized multiscale hybrid multiphase model.

Keywords:

Multiphase flow , Computational multiphase fluid dynamics , Transient flow regime , Hybrid model , Multiscale model