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Modeling Turbulent Liquid/Gas Phase Interfaces using a dual-scale Large Eddy Simulation approach

Event Type: 
Date and Time: 
Friday, April 23, 2021 - 16:30
Location: 
Zoom
Event Sponsor: 
Parviz Moin, Director of Center for Turbulence Research
Speaker(s): 
Prof. Marcus Herrmann

While significant progress has been made in the past decade to predict atomization using detailed numerical simulations, these simulations come at significant computational cost since the range of scales that must be resolved typically exceeds those of a single phase turbulent flow significantly. A switch to a Large Eddy Simulation (LES) approach would be desirable, however, the underlying assumption of LES methods that the dynamics of the unresolved sub-filter scale can be inferred from the dynamics of the resolved scales is questionable when atomization occurs. Similar to viscosity in single-phase flows, surface tension forces scale with the inverse of a length-scale, but unlike viscosity, surface tension can act to either dissipate surface corrugations preventing breakup, giving rise to the Hinze scale/Kolmogorov's critical radius, or enhance surface corrugations due to the Rayleigh-Plateau instability, resulting in breakup. Which process is dominant on the sub-filter scale seems to depend entirely on the sub-filter interfacial geometry, i.e., if the interface is in the shape of ligaments, the surface tension can lead to breakup, whereas in other cases, surface-tension forces can inhibit breakup. Unfortunately, the sub-filter geometry cannot be inferred from the filtered interfacial geometry alone. LES approaches going beyond the traditional single-phase cascade hypothesis may be required for two-phase flows with atomization.

In this presentation, a dual scale LES modeling approach will be discussed that can handle the dual nature of surface tension on the sub-filter scale. The model maintains a fully resolved realization of the phase interface, shifting the modeling task to reconstructing the fully resolved interfacial advection velocity from the filter-scale velocity, taking the effects of sub-filter surface tension, turbulent eddies, and shear into account. Results showing the viability of the dual-scale LES approach in canonical test cases will be discussed.

Link to video file:
Modeling Turbulent Liquid/Gas Phase Interfaces using a dual-scale Large Eddy Simulation approach

Bio: 
Marcus Herrmann is a Professor in the School for Engineering of Matter, Transport and Energy at Arizona State University. He received his PhD in Mechanical Engineering from the Technical University in Aachen, Germany in 2001 and was a post-doc and research associate at CTR and CITS at Stanford University from 2002 to 2007. His research is in the area of computational fluid dynamics for turbulent liquid/gas interfacial flows in both incompressible and supersonic flow environments. His specific area of interest is in understanding and predicting the primary atomization processes of injected liquids with applications ranging from fuel injection systems to medical sprays. He currently serves as the Editor-in-Chief for the Americas of the journal Atomization and Sprays.