TIME: 3:30 PM

LOCATION: GMCS 314

SPEAKER: Perry Johnson, UC, Irvine

ABSTRACT: Direct numerical simulation (DNS) of turbulence is often prohibitively expensive for high Reynolds number flows involving turbulent boundary layers. Therefore, computer simulation of these flows inevitably encounters a trade-off between physical fidelity and computational cost. Reynolds-averaged Navier-Stokes (RANS) has long been the predominant framework for such flows in industry, but interest and feasibility of large-eddy simulation (LES) is growing due to its ability to resolve some of the dominant turbulent motions, albeit at a higher cost that limits its applicability in the design cycle, e.g., for sensitivity analysis or parameter sweeps. In this talk, I will introduce a lower-cost framework for turbulence-resolving simulations of wall-bounded turbulent flows using instantaneous wall-normal integrals. Turbulence-resolving integral simulation (TRIS) is physically motivated by progress in identifying and understanding the prominent role of large- and very-large-scale motions in wall-bounded turbulence. A complete TRIS model implementation is demonstrated for an open channel flow over a wide range of Reynolds numbers, capable of simulating ~10 flow through times in 1 minute on a laptop regardless of Reynolds number, while matching the spectra of large-scale turbulent fluctuations. The outlook for extending this approach to more general turbulent boundary layer flows over immersed bodies will be briefly discussed.

BIO: Perry Johnson earned his Ph.D. in 2017 from Johns Hopkins University, where his work on velocity gradient dynamics in turbulence won the Corrsin-Kovasznay award. He was then a postdoctoral fellow at the Center for Turbulence Research at Stanford University for three years, working on various topics related to small-scale turbulence, multiphase & particle-laden flows, and boundary layers. He joined the Mechanical and Aerospace Engineering department at the University of California, Irvine in 2020 and was promoted to tenure in 2026. He is a recipient of the NSF CAREER, AFOSR YIP, and ONR YIP awards. His research on the turbulence energy cascade was featured in Physics Today, and he co-authored a review of multi-scale velocity gradient dynamics in turbulence for the 2024 Annual Review of Fluid Mechanics. He was selected as a Outstanding Reviewer (top 1%) for the Journal of Fluid Mechanics in 2024.

HOST: Jose Castillo