Dynamics and modeling of small-scale nonlinear and nonhydrostatic phenomena in oceanic flows
Abstract
The overarching focus and long term goal of this proposed work is towards improved understanding and modeling of the small-scale non,linear and nonhydrostatic (N&N) phenomena frequently encountered in different oceanic flows conditions. An important and ubiquitous,example is the interaction of nonlinear internal waves with underwater topographic features such as ridges, sills, straits and islan,ds in the oceanic flows. Other examples include gravity (density) currents that flow over topography in marginal seas into the deep,ocean, and hydraulically controlled flows in narrow channels/passages with varying bottom roughness and environmental conditions. Th,e interplay between such processes and small-scale turbulence and resulting contribution to diapycnal mixing still remains an ongoin,g challenge given the complexity associated with such phenomena. While measurements have provided valuable insights into the dissipa,tion of such nonlinear flows over topography, it is challenging to obtain adeeper understanding of the physics due to difficulty in,collecting sufficient data both spatially and temporally. To this end, highly resolved numerical simulations provide an ideal means,of examining both the energetics and dynamics of such small scale nonlinear and nonhydrostatic flow processes that are often hard to, decipher from the signals observed in the field. The proposed work here seeks to contribute toward this goal through a focused proc,ess-oriented study of such phenomena. In particular, this study aims to systematically explore the dynamics and associated mixing of, nonlinear internal waves with topography. Gravity currents and open channel flows will also be investigated as part of this study.,The main objectives are: (1) to investigate fundamental flow dynamics of nonlinear and nonhydrostatic flow phenomena using high reso,lution numerical modeling studies ranging from nonlinear internal waves breaking over topography to canonical boundary layer turbule,nt flows to gravity currents; (2) to formulate parameterizations for small-scale turbulent mixing driven by such processes and (3) u,pscale modeling approaches to capture such typically unresolved phenomena in realistic field-scale models. This will be achieved thr,ough a concerted effort using highly resolved numerical simulations (both direct numerical simulations (DNS) and large-eddy simulati,ons (LES)) using a combination of both Eulerian and Lagrangian perspectives. Our focus will be on elucidating the small-scale nonlin,ear and nonhydrostatic processes/mechanisms with an eye towards developing parameterizations. Model-data comparisons will be perform,ed to assess, refine and improve the fidelity of the parameterizations. Specifically, detailed parametric studies will be performed,to investigate the fundamental relationships between key mixing parameters widely used in small-scale turbulence. The proposed work,takes a progressive step toward making significant contributions to the strategic ongoing efforts at the Physical Oceanography Progr,am at the Office of Naval Research (ONR) on assessing the effects of small-scale processes which aim to improve understanding of bas,ic physical processes and enhance the fidelity of numerical models of relevance to the Navy.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 10, 2021
- Source ID
- N000142212043
Entities
People
- Subhas K. Venayagamoorthy
Organizations
- Colorado State University
- Office of Naval Research
- United States Navy