January 18th, 2020

Lecturer: Dr. Morteza Derakhti, Senior Research Scientist at the University of Washington’s Applied Physics Laboratory

Number of participants: 8
Number of women among participants: 0

Abstract
Combining high-fidelity numerical modeling and field observations, we examine the characteristics of intermittent wave breaking-inducedturbulence in short-crested wave breaking events. We use a LES/VOF Eulerian-Eulerian polydisperse two-fluid model (Derakhti & Kirby, 2014, 2016) to simulate bubble entrainment and turbulent bubbly flow. Bubble contributions to dissipation and momentum transfer between the water and air phases are considered. Field observations of wave breaking and turbulence by surface following drifters (SWIFTs) include previous (Schwendeman & Thomson 2015, Thomson et al, 2016) and new observations (Dec. 2019) in the North Pacific Ocean. In particular, we reconcile the field measurements of SWIFTs with our numerical model results. Conversion of the model results to a surface-following reference frame, along with scaling of the model domain to match
observations of whitecap coverage, are essential steps. We show that convergence of statistics occurs after approximately 1000-3000 randomly spaced observations in time and space relative to breaking events. We further show important effects of obscuration of velocity measurements due to entrained bubbles on the estimated turbulent dissipation rates. Finally, we examine recent formulations that relate wave dissipation rates to the volume and kinematics of each bubble plume.