| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | February 8, 2016 |
| Latest Amendment Date: | December 14, 2021 |
| Award Number: | 1558978 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Baris Uz
bmuz@nsf.gov (703)292-4557 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | February 1, 2016 |
| End Date: | August 31, 2022 (Estimated) |
| Total Intended Award Amount: | $304,068.00 |
| Total Awarded Amount to Date: | $304,068.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
104 AIRPORT DR STE 2200 CHAPEL HILL NC US 27599-5023 (919)966-3411 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
NC US 27599-3300 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | PHYSICAL OCEANOGRAPHY |
| Primary Program Source: |
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| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Transport by nonlinear internal waves in coastal regions has strong interdisciplinary ties to biological oceanography through transport of plankton and nutrients; geological and geochemical oceanography via transport of sediments; and coastal engineering/management via transport and dispersion of anthropogenic materials such as effluent from sewage outfalls. The overall objectives of this study are to understand the dynamics governing the flux of momentum from shoaling nonlinear internal waves to mean currents; the scale and structure of mean flows driven by shoaling internal waves under idealized conditions; and the magnitude and spatial structure of the net mass transport associated with the shoaling internal waves. Despite the ubiquitous nature of nonlinear internal waves in the coastal ocean, very few three dimensional studies exist that include variability of the topography in the direction normal to propagation. This study represents the first attempt to quantify the transport pathways forced by internal waves and the mean flows generated by them and it is expected to produce results and methodologies with broad applicability in interdisciplinary oceanography and coastal management. The project will support the professional development of a postdoctoral researcher and a graduate student.
The approach is based on a state of the art, three-dimensional, non-hydrostatic numerical model with adaptive mesh capabilities. In addition, data previously collected in Massachusetts Bay during previous studies will be analyzed. This is the first study to systematically address the mean flow and transport driven by nonlinear internal waves shoaling over bathymetry varying in two dimensions. The study comprises two components: a modeling component used to study the transfer of momentum and water mass transport in a variety of situations of increasing realism, and a data-analysis component which will consider the same problem using the extensive dataset available from a series of experiments conducted in Massachusetts Bay over the last 16 years. The modeling component will be used to aid in interpreting the data. The model (Stratified Ocean Model with Adaptive Refinement), developed in part with funding from previous National Science Foundation proposals, is a state-of-the-art three-dimensional non-hydrostatic stratified ocean model which employs adaptive mesh refinement to effectively use the computational resources, increasing resolution on demand where necessary.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The focus of this project was the interaction of waves (internal and surface) with topographic features. The activities involved laboratory experiments, numerical model development and theoretical analysis.
The laboratory and numerical work focused mainly on internal waves. The experimental facility can generate beam waves which can undergo overturning and can drive localized mixing. The numerical model was augmented with an Immersed Boundary package capable of simulating the observed waves. This allows to incorporate topographic features that can be either defined geometrically via a Finite Element model or via a Digital Elevation Model that can be imported from the web given the coordinates of the boundaries.
The table top laboratory experiment has been used to plan a much larger experiment. The experiments were used to train students and postdoc on the use of Background Oriented Schlieren imaging. It produced an impressive dataset convering the propagation of internal wave beams.
The theoretical aspect was mostly concentrated on surface waves.
Specifically, we developed a theory to explain the role of abrupt change in topography in shaping the tail of the distribution of surface wave heights. We handled this process by modifying the Rayleigh distribution through the energetics of second-order theory and a non-homogeneous reformulation of the Khintchine theorem. The resulting probability model reproduced the enhanced tail of the probability distribution of unidirectional wave tank experiments. It also described why the peak of rogue wave probability appears atop the shoal, and explains the influence of depth on variations in peak intensity. Furthermore, we interpreted rogue wave likelihoods in finite depth through the diagram, allowing a quick prediction for the effects of rapid depth change apart from the probability distribution.
We have identified a new parameter that explains how the tail of the distribution of nonlinear surface waves fluctuates around the value predicted by the Rayleigh distribution. This parameter explains why under certain circumstances more extreme waves are observed, whereas in other the number is lower, all relative to the prediction of the Rayleigh distribution.
Last Modified: 06/06/2023
Modified by: Alberto D Scotti
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