JPO_2019_Boundary_Layer_Turbulence_Over_Surface_Waves_in_a_Strongly_Forced_Condition_LES_and_Observation

Published: 30-06-2020| Version 1 | DOI: 10.17632/7m2gpx2vsw.1
Contributors:
Nyla Husain,
Tetsu Hara

Description

This is data for the following publication: Husain, N.T, T. Hara, M.P. Buckley, K. Yousefi, F. Veron, and P.P. Sullivan, 2019: Boundary Layer Turbulence over Surface Waves in a Strongly Forced Condition: LES and Observation. J. Phys. Oceanogr., 49 (8), 1997-2015. This study compares flow field data collected from a large eddy simulation model and particle image velocimetry in a laboratory wind-wave tank experiment of turbulent wind flow over surface gravity waves in strongly forced wind conditions using a wave-following mapped coordinate system. We compare horizontally-averaged mapped profiles of wind speed, wind shear, 2D turbulent kinetic energy, and momentum budget terms, as well as phase-averaged physical and mapped flow fields of wind speed, 2D turbulent kinetic energy, wave stress, and excess turbulent stress. We also include LES results for phase-averaged flow fields of dissipation rate and pressure, as well as surface pressure, turbulent tangential, and turbulent normal stresses. The results show a signature of airflow separation that reduces when the wave slope (ak) and surface roughness parameterization (z_o) are reduced. Airflow separation is stronger and remains closer to the surface in the observational results, which could be the result of roughness elements and wave turbulence that is unresolved in the phase-average. We also ran LES simulations varying the surface roughness parameterization and surface drift velocity along the wave phase to address this disparity, and found that the flow fields are only sensitive to these surface boundary conditions near the crest (and make no difference near the trough). Overall, the comparison between the horizontally- and phase-averaged LES and observational results was reasonable given the idealized LES model set-up - especially for the case of the momentum budget.

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