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The Department of Mechanical, Materials, and Aerospace Engineering welcomes Associate Professor Carlo Scalo of Purdue University, who will give a talk on “Sub-Filter-Scale (SFS) Modeling of Compressible Flows: From High-Reynolds-Number Vortex Dynamics to Hypersonic Boundary Layer Transition and Turbulence” on Monday, July 21 at noon in room 103 of the Rettaliata Engineering Center.

Abstract

This seminar presents recent advances in sub-filter-scale (SFS) modeling for compressible flows across a wide spectrum of regimes, from transitional vortical dynamics to shock-dominated and wall-bounded hypersonic flows. We will first introduce the Coherent-vorticity preserving (CvP) LES technique (Chapelier et al. JCP 2018), which dynamically modulates explicit artificial viscosity closures based on locally sensed spectral content, enabling accurate and efficient resolution of transitional and large-scale coherent structures with minimal implicit numerical dissipation. New developments for high-speed flows called The Quasi-Spectral Viscosity (QSV) and Legendre Spectral Viscosity (LSV) (Sousa and Scalo, JCP 2022, 2023) for the first time unify turbulence modeling and shock capturing in a single spectral-aware closure, offering sharp resolution with minimal dissipation. These techniques allowed for the first dynamic large-eddy simulation of transitional hypersonic boundary layers (Sousa et al. JFM 2024) applied to a passive flow control problem. Other test cases include transitional subsonic and supersonic Taylor–Green vortex breakdown, compressible helical vortex instability, shock-turbulence interactions and high-Mach-number channel flows. In hypersonic regimes, in particular, we prove how the critical interplay between entropy fluctuations at the critical layer, base gradients, and second-mode amplification (Roy and Scalo, JFM, 2025) is not affected by the proposed SFS closures. Together, these models enable accurate, low-cost simulations of multi-scale compressible flows and provide a pathway toward robust predictive tools for turbulent transition in extreme environments. Recent achievements in high-performance computing on very large-scale GPU-accelerated platforms applied to hypersonic flows will also be discussed.

Biography

Carlo Scalo is an associate professor in the School of Mechanical, and Aeronautical and Astronautical Engineering (by courtesy) at Purdue University. He completed his postdoctoral appointment (2014) at Stanford University working on theoretical and numerical modelling of thermoacoustic instability and sound-turbulence interactions in compressible boundary layers. Prior to that, he obtained his Ph.D. (2012) from Queen's University, Canada, working on subgrid-scale modeling of high-Schmidt-number turbulent mass transfer in equilibrium and non-equilibrium geophysical flows. He obtained his B.Eng. (2006) and M.S. (2008) degrees in aerospace engineering at the Universita’ degli Studi di Napoli—Federico II, Italy.

Scalo has developed computational techniques for prediction of acoustic noise propagation and control in hypersonic boundary layers, low-speed and high-speed transitional and fully developed turbulence and thermoacoustic instability in combustion systems. Scalo has received three distinct Young Investigator Program (YIP) awards from the Department of Defense in hypersonic boundary layer transition (Air Force), hypersonic boundary layer turbulence (Navy) and vortex dynamics (Army).

Scalo is also the founder of HySonic Technologies—a Purdue start-up that has received funding from ONR, DARPA, Army, and various primes for the design of a new generation of ultrasonically absorptive aeroshells for hypersonic vehicles, acoustic liners for passive control of thermoacoustic waves in high-speed propulsion systems and a new class of solid-fuel-powered hypersonic air breathers.

Finally, Scalo joined the US Navy's Joint Hypersonics Transition Office (JHTO) as subject matter expert (SME) for one year (March 2024–March 2025) developing basic and applied research, and workforce development programs in hypersonics.