The internal wave field radiated by a stratified turbulent wake

Presenter: 
Peter Diamessis, Cornell University
Event Location: 
BCCMWS 100
Event Date: 
Thursday, March 5, 2015 - 3:00pm
Event Type: 
SCMSS Seminar Series

Abstract

This talk will present results from large eddy simulations (LES) of a stratified turbulent wake of a towed sphere over a broad range of body-based Reynolds number and Froude numbers. This canonical flow serves as an idealized model of the wake flows of topographic features and underwater submersibles in the oceanic pycnocline. Following an introduction on the fundamentals of stratified turbulence and internal gravity waves (IGWs), the focus will be on the wake-radiated IGW field and the distinct variations in its properties with increasing Reynolds numbers. At the higher Reynolds numbers values examined by the LES, which are one order of magnitude higher than those attained in the laboratory, secondary Kelvin-Helmholtz instabilities and turbulence in the wake core drive persistent IGW radiation up to much later times than commonly expected. Through two-dimensional wavelet analysis, the wavelengths, group/phase velocities and orientation angle of the wake-emitted IGW field are estimated. At the higher Reynolds number value, IGW beams/packets propagate at an angle closer to the horizontal plane suggesting that the wave-generation mechanism is no longer viscously controlled but serves to efficiently extract momentum from the mean wake flow. The steepness of the near-field waves increases with Reynolds and Froude number, indicating potential for enhanced remote wave breaking in geophysical/naval environments. Finally, recent results on the potential of these waves to generate a distinct surface signature will be discussed.

Speaker Information

Peter Diamessis received his B.S. from the National Technical University of Athens (NTUA), Greece in 1995 and his Ph.D. from the University of California at San Diego (with a specialization in fluid mechanics) in 2001. Following 4.5 years as a postdoc at the University of Southern California, he joined the faculty at Cornell’s School of Civil and Environmental Engineering, where he has been an Associate Professor since 2011. His computationally-focused research interests include the study of stratified turbulent wakes, nonlinear effects in internal waves and instability/turbulence/resuspension under internal/surface solitary waves and the development of high-accuracy/resolution element-based numerical methods with a high-performance-computing-focus.

Peter's research website can be found here.