Computational multi-scale modeling of super-dispersed multiphase flows

Within IMPACT groups there is interest in super-dispersed multiphase flows including liquid flows with very large numbers of dispersed and interacting bubbles, or solid particles, gas flows with very large numbers of solid particles or evaporating, condensing and coalescing droplets. Multiphase flows are defined as ‘super-dispersed’ when it is no longer possible to simulate particle trajectories individually within the domain of interest, simply because the number of particles is too large. Nonetheless, the goal is to design, test and apply numerical solution strategies to accurately solve both fluid-particle and air-droplet interactions.

When modeling on micro scale is not feasible, or data handling too heavy, a macro scale continuum model involving averages is used to reduce the number of degrees of freedom and complexity in both numerical calculations, and physical and mathematical description. There are numerous physical systems where this type of reduction is readily possible and accurate. However, for many others such a reduction is unknown and/or unavailable in closed form. Computational modeling of super-dispersed multiphase gas-droplets and particulate flows will be investigated by bringing them together within one strategy, so-called Heterogeneous Multi-scale Modeling (HMM).

To assess the potential of HMM for super-dispersed multiphase flows in industrial settings, the following questions will be addressed:

1)	How can HMM be used successfully? In particular, how is it usable in the three challenging applications in which too many particulates are present to allow micro scale modeling?

2)	What are the accuracy and robustness of HMM for simplifying limits in which overall micro scale modeling is feasible?

3)	What is the overall convergence and computational speed of the multi-scale methods?

Specific projects/applications can be found in (i) turbulent air-water-droplet flows with phase transitions and hydrophobic behaviour, (ii) dry granular flows and wet particle-liquid slurries, and (iii) multiple condensing and coalescing water droplets in air flows.