Disk wakes in nonlinear stratification

D Gola, S Nidhan, JL Ortiz-Tarin, HT Pham… - Journal of Fluid …, 2023 - cambridge.org
Journal of Fluid Mechanics, 2023cambridge.org
Nonlinearity of density stratification modulates buoyancy effects. We report results from a
body-inclusive large eddy simulation of a wake in nonlinear stratification, specifically for a
circular disk at diameter-based Reynolds number () for all the profiles is the same. The first
part of the study investigates the centred cases. Non-uniform stratification results in
increasing wake turbulence relative to the benchmark owing to reduced suppression of
turbulence production as well as wave trapping in the pycnocline. Steady lee waves are also …
Nonlinearity of density stratification modulates buoyancy effects. We report results from a body-inclusive large eddy simulation of a wake in nonlinear stratification, specifically for a circular disk at diameter-based Reynolds number () for all the profiles is the same. The first part of the study investigates the centred cases. Non-uniform stratification results in increasing wake turbulence relative to the benchmark owing to reduced suppression of turbulence production as well as wave trapping in the pycnocline. Steady lee waves are also quantified to understand the limitations of linear theory. The second part pays attention to the effect of a relative shift between the pycnocline and the disk. The wake defect velocity decays substantially faster in the cases with a shift and the wake has higher turbulence level. The effect of disk location on the Kelvin wake waves (a family of steady waves within the pycnocline) and its modal form is obtained and explained by solving the Taylor–Goldstein equation. The family of unsteady internal gravity waves that are generated by the wake is also studied and the effect of disk shift is quantified.
Cambridge University Press
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