Multiscale Computational Modeling of High-Speed Flows: From Continuum to Rarefied Regimes

Ozgur Tumuklu, PhD
Rensselaer Polytechnic Institute

Abstract: Hypersonic shock wave boundary layer interactions (SWBLIs) have been a topic of intense research due to their potential to induce laminar to turbulent transition, instabilities, and localized high-pressure and heating regions, as shown in figure. Accurately predicting these phenomena, particularly in the presence of thermochemical nonequilibrium, is critical for effective design. Over the years, numerous experimental, theoretical, and numerical studies have advanced our understanding of SWBLIs. Among the various numerical approaches, simulations have emerged as a cost-effective method for investigating the complex behavior of hypersonic flows, particularly with the advent of massive parallel computing platforms. Recent advancements in both continuum and kinetic methods have provided researchers with diverse tools to study these interactions. The Direct Simulation Monte Carlo (DSMC) method, a powerful kinetic approach for emulating the Boltzmann transport equation, is particularly effective for rarefied gas flows, but becomes computationally prohibitive for higher-density conditions. On the other hand, continuum approaches offer a more efficient alternative for these regimes. In this seminar, I will provide an overview of the DSMC method as applied to shock-dominated flows and compare its performance with continuum-based methods. The presentation will cover key aspects of the DSMC approach and showcase its applications and findings from my research group, the HAVA Lab. Additionally, I will discuss turbulence models for continuum shock-dominated flows and turbulent jet expansions, highlighting their practical applications.

Biography: Dr. Tumuklu earned his Ph.D. from the University of Illinois at Urbana Champaign in 2018, with a specialized focus on hypersonic flow instabilities utilizing kinetic approaches. Subsequent to his doctoral studies, he engaged in a role as a postdoctoral researcher within the Artemis project at NASA's Jet Propulsion Laboratory. Following his time at NASA JPL, Dr. Tumuklu directed his efforts towards the advancement of software tools at the University of Arizona. These tools were designed to facilitate the investigation of a broad spectrum of flows, ranging from subsonic to hypersonic, and spanning the continuum to rarefied regimes.His expertise and research pursuits encompass the realm of computational physics, with a pronounced emphasis on rarefied nonequilibrium flows and the development of stability analysis methodologies for hypersonic reacting flows. Dr. Tumuklu's proficiency extends to open-source software development, data-driven techniques, and the application of highperformance computing to scientific software endeavors. More information is available on the group's website, https://www.havalab.org/.