Award Abstract # 2048844
Collaborative Research: Experimental and Numerical Study of Bed Shear Stress and Turbulent Boundary Layer Structure Induced by Breaking-Wave-Generated Vortices

NSF Org: OCE
Division Of Ocean Sciences
Recipient: UNIVERSITY OF DELAWARE
Initial Amendment Date: January 22, 2021
Latest Amendment Date: May 20, 2021
Award Number: 2048844
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: July 1, 2021
End Date: June 30, 2024 (Estimated)
Total Intended Award Amount: $390,198.00
Total Awarded Amount to Date: $390,198.00
Funds Obligated to Date: FY 2021 = $390,198.00
History of Investigator:
  • James Kirby (Principal Investigator)
    kirby@udel.edu
Recipient Sponsored Research Office: University of Delaware
550 S COLLEGE AVE
NEWARK
DE  US  19713-1324
(302)831-2136
Sponsor Congressional District: 00
Primary Place of Performance: University of Delaware
210 Hullihen Hall
Newark
DE  US  19716-1551
Primary Place of Performance
Congressional District:
00
Unique Entity Identifier (UEI): T72NHKM259N3
Parent UEI:
NSF Program(s): PHYSICAL OCEANOGRAPHY
Primary Program Source: 01002122DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 9150
Program Element Code(s): 161000
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.050

ABSTRACT

This research aims to improve the understanding of breaking wave vortices impinging on the seabed. This has broad impacts on the prediction of a wide range of near-shore processes where wave breaking is fundamental in driving the sediment transport and resulting morphological changes. Detailed laboratory experiments will provide a high quality, comprehensive data set to test and improve a numerical model to better resolve the effects of wave breaking and eddy impingement on the bottom boundary layer structure. In return, the validated model will provide more detailed information to help interpret the measured data as well as a valuable research tool to model prototype wave conditions not reproducible in the laboratory. This research project would benefit society by enabling the development of better engineering tools for coastal zone management and mitigation of coastal hazards. The project will support two PhD students, one at South Dakota State University (SDSU) and another at the University of Delaware (UD), and will provide an opportunity for the new PhD program at SDSU to grow through research collaboration with an established research center. The PhD student from UD will participate in a portion of the experimental program at SDSU and work with the SDSU PhD student on model/data comparison. He/she will also work for a period at the University of Washington (UW) during the development of needed model extensions. To broaden the impacts of the research on STEM education, the lead PI will design a new technical elective on advanced fluid mechanics laboratory, which will be offered to undergraduate seniors and graduate students. The course will include a suite of experiments to give students hands-on experience with measuring bed shear stresses in steady and unsteady flows using different experimental techniques and approaches, emphasizing the importance of careful experimentation and analysis to produce high-quality, reproducible results.

The objective of this research is to understand the structure of the bottom boundary layer and determine the bed shear stresses induced by the impact of breaking-wave-generated vortices on a plane beach. Laboratory experiments will be conducted in a 25 m-long, 0.9 m-wide and 0.75 m-deep tilting flume equipped with a programmable wave generator. The turbulent velocity fields under spilling and plunging waves will be measured in a three-dimensional (3D) flow volume on smooth and rough beds using a volumetric three-component velocimetry (V3V) system. The measured data will be used to study the momentum balance in the near-bed region and to develop more accurate methods for estimating the bed shear stresses in the unsteady, non-equilibrium boundary layer associated with breaking waves. The measured data will also be used to validate a multi-phase (air-water) large eddy simulation (LES) scheme for breaking waves, already shown to accurately describe the processes of wave breaking and eddy formation and evolution, to better resolve eddy impingement on the bottom and resulting modifications to the boundary layer structure.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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