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Title: Wake Vortices and Dissipation in a Tidally Modulated Flow Past a Three‐Dimensional Topography

Large eddy simulations are employed to investigate the role of tidal modulation strength on wake vortices and dissipation in flow past three‐dimensional topography, specifically a conical abyssal hill. The barotropic current is of the formUc + Ut sin(Ωtt), whereUcandUtare the mean and oscillatory components, respectively, and Ωtis the tidal frequency. A regime with strong stratification and weak rotation is considered. The velocity ratioR = Ut/Ucis varied from 0 to 1. Simulation results show that the frequency of wake vortices reduces gradually with increasingRfrom its natural shedding frequency atR = 0 to Ωt/2 whenR ≥ 0.2. The ratio ofRand the excursion number, denoted as, controls the shift in the vortex frequency. When, vortices are trapped in the wake during tidal deceleration, extending the vortex shedding cycle to two tidal cycles. Elevated dissipation rates in the obstacle lee are observed in the lateral shear layer, hydraulic jet, and the near wake. The regions of strong dissipation are spatially intermittent, with values exceedingduring the maximum‐velocity phase, whereDis the base diameter of the hill. The maximum dissipation rate during the tidal cycle increases monotonically withRin the downstream wake. Additionally, the normalized area‐integrated dissipation rate in the hydraulic response region scales withRas (1 + R)4. Results show that the wake dissipation energetically dominates the internal wave flux in this class of low‐Froude number geophysical flows.

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Author(s) / Creator(s):
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DOI PREFIX: 10.1029
Date Published:
Journal Name:
Journal of Geophysical Research: Oceans
Medium: X
Sponsoring Org:
National Science Foundation
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