|Dr Ted Cox|
University College Dublin
|Professor Matthias Ihme|
|Third speaker TBA|
Dr Ted Cox
University College Dublin, Ireland
Shock reflection in dense gases and other problems. A lecture dedicated to the memory of Professor Alfred Kluwick.
Ted Cox is an Associate Professor of Applied and Computational Mathematics in the School of Mathematics and Statistics in University College Dublin. Ted’s research is in fluid mechanics with a special interest in wave-propagation phenomena, nonlinear waves in dense gases, and perturbation analysis. Ted’s collaboration with Alfred Kluwick first started in 1989 and has resulted in research publications in transonic dense gas flows, two-layer fluid flows, resonant dense gas oscillations and nonclassical shock phenomena. Ted has taught a wide variety of courses in Applied Mathematics in University College Dublin over the last 39 years. He was involved in setting up an MSc in Computational Science and more recently he secured funding for the design and delivery of a Computation for Scientists module aimed at first year science students. Since 2020, Ted has been Head of the School of Mathematics and Statistics.
Professor Matthias Ihme
Stanford University, USA
Crossing the ridge: How does the Widom line affects the physical behavior of supercritical fluids?
Over recent years, significant progress has been made towards the modeling and physical understanding of high-pressure supercritical flows. The thermodynamic state-space in the supercritical region exhibits high complexity that includes the critical point, strong non-linearities in the thermodynamic response and distinct transition regions, such as the Widom lines, that demarcate transitions from liquid- like to vapor-like conditions. In this talk, we will employ complementary analysis and modeling techniques to examine the effects of this complex thermodynamic state-space by considering three problems that are of relevance to high-pressure applications.
The first problem considers the instability of binary mixing layers at supercritical conditions. Strong variations in thermodynamic response across the Widom line introduce complex interaction between Widom-line-transition and the hydrodynamic inflection point. Employing classical stability analysis, we present a novel instability mechanism that has the net effect of destabilizing the mixing layer at conditions near the critical point, thereby offering opportunities for improving fuel injection strategies at high-pressure operating conditions.
Related to the injection of liquid fuels, we proceed by examining evaporation processes in supercritical environments. To this end, an interface-resolving diffuse-interface method and molecular- dynamic simulations are employed to explore the underlying phase-exchange mechanisms that are manifested as transition between subcritical evaporation and supercritical dense-fluid-mixing. With this, a regime diagram is developed to identify four distinct regimes of evaporation/mixing behaviors. The importance of the Widom-line is identified as a key mechanism for introducing substantially different interface phase exchange processes that have so far not been considered in explaining supercritical evaporation processes.
The third problem will focus on examining the coupling of phase transition and ignition at real- fluid environments. To this end, a compressible solver with a real-fluid state equation and finite-rate chemistry is employed. Simulations of a high-pressure diesel-fuel injector are performed. By considering different operating points of increasing proximity to the Widom line, we will isolate effects of the real-fluid environment and low-temperature chemistry. Implications of these finding for low-emission combustion strategies will be discussed.
We close this presentation by discussing open research issues and further research directions in the physical understanding and accurate modeling of supercritical fluids.
Matthias Ihme is Professor in the Department of Mechanical Engineering and the Department of Photon Sciences at Stanford University. He holds a BSc. degree in Mechanical Engineering and a MSc. degree in Computational Engineering. In 2008, he received his Ph.D. in Mechanical Engineering from Stanford. After being on the faculty of the Aerospace Engineering Department at the University of Michigan for five years, he returned to Stanford in 2013. He is a recipient of the NSF CAREER Award (2009), the ONR Young Investigator Award (2010), the AFOSR Young Investigator Award (2010), the NASA Early Career Faculty Award (2015), and the Hiroshi Tsuji Early Career Research Award (2017). His research interests are broadly on the computational modeling of reacting flows, the development of numerical methods, and the investigation of advanced combustion concepts.
Workshop on non-ideal computational fluid dynamics (niCFD)
This workshop aims to introduce and have an open discussion on the use of NICFD RANS solvers within the context of typical engineering application involving NICFD flows. An open test case and set of reference data will be provided by the session organisers and interested participants will be able to performance simulations and share their results.
- Evaluate the accuracy of existing NICFD-RANS solvers
- Develop best practices for efficient numerical simulations of NICFD flows
- Educate the next-generation of engineers and practitioners to the use of NICFD models
- TU Delft’s supersonic linear cascade operating with siloxane MM in non-ideal thermodynamic conditions
Workshop on advances in NICFD experimental test facilities
This workshop will take the form of a panel discussion and will explore current advances in experimental test facilities that have been commissioned to explore NICFD fluid flows. Each invited panellist will be provide a short introduction of existing test facilities from their institution including a summary of capabilities and on-going research directions. This will be followed by an open discussion to explore on-going challenges related to experimental aspects alongside further research directions.