Abstract:
The dynamics of immiscible interfaces in turbulent flows undergoing frequent topological changes are governed by processes that occur on a range of scales that exceeds those of a single phase turbulent flow significantly. This results in prohibitive numerical cost of simulations that aim to resolve all relevant scales in a direct numerical simulation approach. 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 resolved scales is questionable when atomization occurs under shear or acceleration. Surface tension plays a crucial role in breakup and its role of either stabilizing or destabilizing the interface is determined by the small scale geometry of the interface that may be difficult to infer from the filter scale geometry of the interface alone.
In this talk, both a dual scale LES modeling approach and a more traditional hybrid LES/DNS adaptive mesh refinement (AMR) approach will be discussed that can handle the dual nature of surface tension on the LES sub-filter scale. Both approaches maintain a fully resolved realization of the phase interface on an embedded DNS scale mesh, shifting the modeling task from finding closure models in the filtered equations to reconstructing a DNS scale interfacial advection velocity. The unclosed LES terms related to the phase interface can then be closed directly by explicit filtering in the dual scale approach, or are non-existent in the first place in the hybrid LES/DNS AMR approach. Results showing the viability and shortcomings of both approaches in canonical test cases will be discussed.
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 the Center for Turbulence Research and the Center for Integrated Turbulence Simulations 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 Chair of the Institute of Liquid Atomization and Sprays Systems (ILASS) in the Americas and as the Editor-in-Chief for the Americas of the journal Atomization and Sprays.