# Research

The McKeon research group researches fundamental and applied problems related to fluid flow, especially close to surfaces. The focus is on challenges related to aerospace, hydrodynamics, the fluid dynamics of bioinspired design, and engineering in general, using novel experiments and analysis techniques.

We have current research activity related to characterizing the fundamental structure of turbulent boundary layers; to efficient and high-fidelity low-order models of wall turbulence, especially by extending the resolvent analysis for turbulent flows which we have been developing for several years; and to flow modeling exploiting both computational and experimental data through data assimilation frameworks.

## Current Research Highlights

## Familiar Patterns in Strongly Viscoelastic Turbulence

*We use linear stability techniques and resolvent analysis to give insight into the structure of turbulent flow of a polymer-doped fluid.*

## Structural Analysis of Turbulent Boundary Layers

*We leverage integral measurements of a passive scalar to identify structurally important velocity scales in boundary layers.*

## Resolvent Analysis: Compressibility Effects, Scalar Dynamics, and Analytic Approximations

*Extensions of the resolvent framework for a wider variety of applications in wall-bounded turbulence*

## A Take on Turbulence: Singing into Chaos

*Leveraging the idea of coherent structures in turbulent flows, we seek to study the response of this complex system to a known synthetic structure. *

## Systematic Design of Feedback Flow Control for Turbulent Drag Reduction

*Taming turbulence: we develop systematic approaches to design flow control schemes to reduce drag on the next generation of ships, airplanes and other engineering systems.*

## Influence of Mechanical System Design on the Response of an Airfoil to Predicted, Coherent Fluid Forcing

*How should we design an engineering system to leverage a predicted incoming flow field for improved drag reduction?*

## Study of Unsteady Flow Phenomena via Cyber-Physical Fluid Dynamics

*Combining cyber-physical fluid dynamics and Koopman analysis in order to study forced fluid-structure systems.*

## Reduced Order Modeling of Rotationally Driven Flows

*It seems doubtful whether we can expect to understand fully the instability of a fluid flow without obtaining a mathematical representation of the motion of the fluid in some particular case in which instability can actually be observed. – G. I. Taylor (1923)
*

## A Resolvent-based Model for Roughness-induced Scale Interactions in a Turbulent Boundary Layer

*By modeling a turbulent boundary layer as a low-order linear system with random background forcing, we are able to qualitatively predict the effect of a rough wall on the individual scales of the turbulence.*

## Tollmien-Schlichting waves and the Elasto-Inertial Instability

*Transition in the flow of highly viscoelastic fluids has its origins in a classical Newtonian flow pattern*