Structures in a turbulent boundary layer – their coherent transport behavior and unsteady response
Arizona State University
Abstract
With the advances in scale-resolving measurement techniques for complex flow environments, we have gained a mature understanding of dominant coherent structures that populate canonical turbulent boundary layers. For this seminar, we discuss two examples of the complex interplay of turbulent scales that significantly affects the world we live in. First, we look at the dispersion of a passive scalar plume that is injected into a high Reynolds number (Re) turbulent boundary layer using simultaneous planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV). We focus on the role of the large coherent structures that populate such boundary layers on the break-up, meandering, and dispersion of the scalar plume at early stage. These structures significantly alter the long-range concentration intermittency and instantaneous concentrations further downstream – understanding which is critical for modeling pollutant, aerosol, and particulate transport in atmospheric boundary layers over complex terrains. In a second contrasting example, we present preliminary efforts where we can externally perturb these flows and coherent mechanisms to mimic real-world unsteadiness (such as gusts, vortex-wing interactions, etc.). We do this to study the ensuing changes to the boundary layer behavior such as separation, scalar transport, etc. To this end, we present a ‘Translating Rotating Cylinder’, ‘Dynamic Aspiration System’, and a class of herringbone-type 2D and 3D roughness patterns to discuss their effects.
About the speaker
Dr. Gokul Pathikonda is an Assistant Professor in the School for Engineering of Matter, Transport and Energy (SEMTE) at Arizona State University. His team designs laboratory experiments to identify and measure fundamental turbulence behavior relevant to aerospace, energy, astrophysics, maritime and atmospheric sciences. Specifically, they design innovative boundary layer control approaches and hybrid application of laser-based techniques (particle image velocimetry, laser-induced fluorescence, etc.) to study wall-bounded turbulent flows, shear-driven turbulent mixing, and reacting flows. He is a recipient of 2025 ONR Young Investigator Award, Stanley Weiss Outstanding Dissertation Award and RISE Fellowship. He received his Ph.D. in 2017 in Theoretical and Applied Mechanics from University of Illinois, Urbana-Champaign, and was a researcher at Georgia Tech, Indian Institute of Science and Jawaharlal Nehru Center for Advanced Scientific Research at Bangalore.
