Department of Mechanical Engineering
VIRTUAL GRADUATE SEMINAR IN FLUID MECHANICS
Join on-line via Zoom: https://wse.zoom.us/j/93762992307
Friday, October 9, 2020
4:00 p.m. – 5:00 p.m. (EDT)
“Deep Operator Neural Networks (DeepONets) for Prediction of Instability Waves in High-Speed Boundary Layers”
Presented by PATRICIO CLARK DI LEONI
(Advisers: Profs. Charles Meneveau & Tamer Zaki)
We show how DeepONets can predict the amplification of instability waves in high-speed flows. In contrast to traditional networks that are intended to approximate functions, DeepOnets are designed to approximate operators and functionals. Using this framework, we train a DeepONet that takes as inputs an upstream disturbance and a downstream location of interest, and provide as output the amplified profile at the downstream position in the boundary layer. DeepONet thus approximates the linearlized Navier-Stokes operator for this flow. Once trained, the network can perform predictions of the downstream flow for a wide variety of inflow conditions without the need to calculate the whole trajectory of the perturbations, and at a very small computational cost compared to discretization of the original flow equations.
“The Effect of Seams on the Aerodynamics of Baseballs: A Computational Study”
Presented by JOHN SCHEFFEY
(Adviser: Prof. Rajat Mittal)
The aerodynamic force on a ball due to its rotation, known as the Magnus effect, has long been observed and studied in baseball and other ball sports. Experimental studies have examined the effects of pitch speed, spin rate, and seam height on these forces, but the underlying effect of the presence of a seam is not as well understood. Recently, there has been interest in the potential existence of “non-Magnus” forces, which are thought to be caused by certain seam orientations in ball flight. In this study, we present numerical simulations of flows past rotating spheres at varying orientation angles of rotation and investigate the effects of baseball seams on the aerodynamics of such bodies. Simulations are performed at Reynolds numbers of 500 and 1000 and spin ratios of 0.25 and 0.5. We examine the role that baseball seams play in modifying the wake and producing asymmetry, leading to transverse forces that generate deviations in the trajectory of pitched and batted balls.