Session: 10.1 - Boundary layer flows

Paper Number: 171484

171484 - Track Keynote - Simulation and modeling of non-canonical turbulent boundary layers 

Abstract: 

The bulk of wall turbulence research has focused disproportionately on canonical flows along smooth flat plates with uniform freestream conditions. However, in engineering and environmental applications, such as flow around hydraulic turbine blades, navy platforms, and in rivers, most flows are dynamically complex, affected by surface roughness, surface curvature, wall permeability, and unsteadiness, etc. The consequence is that existing descriptions and models of turbulence have limited utility to design practice. My goal is to build essential physics into models, to enable a consistent description for turbulence across a wide range of flow complexities. The talk will start with understanding and modeling for rough-walled, equilibrium or non-equilibrium turbulent boundary layers subjected to longitudinal pressure gradients. Using data from direct and large-eddy simulations (DNS and LES), I will show that wall roughness significantly modifies turbulence under strong spatial or temporal variations. Data and insights are used to inform roughness-unresolved turbulence closures, such as linear eddy-viscosity models, which have long-time challenges in accurately predicting non-canonical turbulent flows or those with arbitrary roughness. The second part of the talk is on using DNS to better understand important transport processes of water and solutes in riverine systems—natural turbulent flows bounded by rough, permeable walls. A knowledge gap exists on how dynamics at the sediment grain scale affect multiscale hydrologic and biogeochemical processes. I will show that sediment roughness—typically ignored in existing predictive approaches—is an important drive of transport in nature. 

Presenting Author: Junlin Yuan Michigan State University

Presenting Author Biography: