Tidally dominated flow past a three-dimensional topography: wake dynamics, energetics and mixing*

The wake generated as a result of ocean currents interacting with bottom topography plays a significant role in dissipation, mixing, and the ocean energy budget.  The challenges associated with direct measurement of these dynamic quantities, or their estimation using bulk properties of the flow and stratification, warrants numerical investigations using three-dimensional turbulence resolving simulations.  Motivated by the variability of boundary currents, we perform Large Eddy Simulations of tidally dominated flows past an idealized underwater hill in the presence of background rotation and stratification.  Specifically, we investigate the interaction of currents modeled as a superposition of a background and a tidal component, U(t) = U_c + U_tsin(ωt), with a dynamically tall three-dimensional topography that exhibits partial upstream blocking.  The five cases of tidally dominated flows (U_t/U_c ≥ 1) investigated present considerably different wake dynamics compared to the tidally modulated flows (U_t/U_c < 1) presented in Puthan et al. (2022).  The variation in dissipation, mixing, buoyancy flux, and diapycnal diffusivity are quantified and compared for the five cases investigated.  Comparisons are also made with observational measurements from Palau.

Puthan, P., Pawlak, G., & Sarkar, S. (2022). Wake vortices and dissipation in a tidally modulated flow past a three‐dimensional topography. Journal of Geophysical Research: Oceans, 127(8).