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DESCRIPTION:Speaker: Perry Johnson, UCI
Talk Title: Two Fundamental Relations for Turbulent Flows
Abstract: wo fundamental effects of turbulence are (a) an increased rate at which kinetic energy is dissipated into heat and (b) an enhanced momentum (and heat) flux across boundary layers leading to much higher skin friction drag forces (and surface heat transfer). This presentation will introduce and apply two exact relations related to these fundamental effects, respectively. First, the concept of Stokes Flow Regularization (SFR) provides an exact expression for the scale-wise energy cascade rate in terms of vortex stretching and strain-rate self-amplification. Applied to data from fully-resolved simulations, this precisely quantifies the mechanisms responsible for generating large dissipation rates at small scales. SFR also serves as an intriguing alternative to spatial filtering as the basis of large-eddy simulation modeling. Specific potential modeling advantages will be discussed. Second, the Angular Momentum Integral (AMI) equation for turbulent boundary layers will be introduced. The AMI equation quantifies the impact of various flow phenomena throughout a boundary layer flow on the skin friction relative to a baseline laminar flow. An analogous integral equation for the surface heat transfer will also be introduced. Together, these provide a powerful method for probing flow data in terms of key engineering quantities of interest. Example applications for AMI-based analysis will be shown for boundary layer transition and supersonic turbulent boundary layers.
Biography: Perry Johnson Perry Johnson earned his Ph.D. in 2017 from Johns Hopkins University (advisor: Charles Meneveau), 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 as an assistant professor. His recent research on the energy cascade was featured in Physics Today, and his forthcoming review of multi-scale velocity gradient dynamics will appear in the next issue of Annual Review of Fluid Mechanics.
Host: AME Department
More Info: https://ame.usc.edu/seminars/
Webcast: https://usc.zoom.us/j/98121141178?pwd=VGEyaXVWYnRaazFYWUVhbVAycGVWQT09 Meeting ID: 981 2114 1178 Passcode: NhXrDOqQU8
SEQUENCE:5
DTSTART:20230920T153000
LOCATION:SSH 202
DTSTAMP:20230920T153000
SUMMARY:AME Seminar
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DTEND:20230920T163000
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