
NSF Org: |
CMMI Division of Civil, Mechanical, and Manufacturing Innovation |
Recipient: |
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Initial Amendment Date: | August 22, 2011 |
Latest Amendment Date: | November 8, 2011 |
Award Number: | 1135026 |
Award Instrument: | Standard Grant |
Program Manager: |
Richard Fragaszy
CMMI Division of Civil, Mechanical, and Manufacturing Innovation ENG Directorate for Engineering |
Start Date: | October 1, 2011 |
End Date: | September 30, 2017 (Estimated) |
Total Intended Award Amount: | $1,274,980.00 |
Total Awarded Amount to Date: | $1,274,980.00 |
Funds Obligated to Date: |
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History of Investigator: |
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Recipient Sponsored Research Office: |
51 COLLEGE RD DURHAM NH US 03824-2620 (603)862-2172 |
Sponsor Congressional District: |
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Primary Place of Performance: |
Kingsbury Hall, UNH Durham NH US 03824-2619 |
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): | NEES RESEARCH |
Primary Program Source: |
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Program Reference Code(s): |
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Program Element Code(s): |
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Award Agency Code: | 4900 |
Fund Agency Code: | 4900 |
Assistance Listing Number(s): | 47.041 |
ABSTRACT
The destruction from earthquake-induced tsunamis in the U.S. and other Pacific Rim countries can result in considerably more damage and deaths than the seismic ground motion. The goal of tsunami research is to save lives and reduce economic losses. To do this, we must develop sufficient scientific knowledge and appropriate engineering tools on which to base comprehensive tsunami mitigation plans and communicate this information effectively to decision makers, the emergency planning community and the public. The overarching theme of this effort is to formulate the complex processes affecting our coastal structures that are driven or affected by turbulent coherent structures (TCS). The role of wall bounded TCS in multiple forcing environments will be examined. Near the seabed, sediment pickup and transport can be significantly enhanced by TCS, leading to extreme scour and infrastructure failure. In the horizontal plane, TCS can appear as giant whirlpools and are commonly associated with extreme damage in ports and harbors. Extensive experiments will be performed at the Oregon State University (OSU), using the Large Wave Flume (LWF) to study the fine detail of TCS significance on nearbed processes, such as mobilization and transport of sediment, as well as the Tsunami Wave Basin (TWB) to characterize the complete hydrodynamic structure of a large, horizontal TCS generated by a port. The observations will be complimented with a wide-reaching numerical effort. To study the detailed TCS generation and its effects on sediment suspension due to transient long wave motion, we will use 3D turbulence resolving simulation models, with grid resolutions on the order of 1 mm. Fully coupled with the flow models will be Discrete Element Models for individual sediment particles, permitting grain-resolving simulation of tsunami-induced transport. Coupling the LWF and the TWB results with the fine resolution numerical tools will allow for predictions of bed mobilization, scour, and harbor wall forces for a generic tsunami problem, including the combined forcing of the mean "uniform" tsunami flow and the very localized, complex velocities due to TCS.
The broader impacts of the proposed activities are to ultimately reduce the loss of life and property due to tsunamis through assessing population at risk needs to be aware of the associated risk and be prepared to respond in case of a tsunami warning. Here, we take a two-pronged approach to public education of the hazards possible during a tsunami event. First, a program targeting middle and high school students in coastal states will be closely connected to the experimental research proposed in the TWB. Students will formulate a harbor tsunami response plan, that will be implemented and tested in the TWB. Second, we identify several ways to enhance the transfer of our intellectual efforts to various stakeholders. Our knowledge transfer to engineering practitioners will take the place with 2-3 webinars regarding harbor design, sediment scour, and sediment liquefaction. These webinars will provide information regarding both existing design practices as well as new knowledge gained. The practitioners will be receiving professional development credit and the sessions will be recorded on the NEESHub for future use.
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.
Harbors, bridges, navigation channels, jetties, power grids, beaches and sand dunes are critical infrastructures and landforms directly affecting the prosperity and sustainability of coastal communities. Due to the threat of sea level rise and increased storm intensity, conventional design and management guidelines for these coastal infrastructures and landforms become inadequate because they are developed mainly using averaged coastal forcing. Our study aim was to understand and model various turbulent coherent structures (vorticites) in shallow nearshore environments subject to extreme waves. These coherent structures are intermittent features but may impose major and sometimes catastrophic impacts to beach morphology and stability of structures.
Our work approached these problems with a framework combining both physical experiment and numerical modeling. The physical experimental work focused on resolving dynamics of coherent structure generation on the boundary layer scale, affecting sediment transport and scour, and on the harbor scale, affecting ship traffic and safety. Using these data, two-phase (sediment, water) numerical modeling of both scenarios were developed for open-source use.
The sediment transport mechanisms associated with coherent structure development and shedding were observed with experiments in a full-scale 2D large wave flume facility. The flume is 110 m long and capable of generating full scale waves over a real sediment bed. Our study focused on observing dynamics under waves, solitary waves (tsunami), and waves combined with solitary waves over a sandy rippled bed as well as around a pipeline feature positioned on a sandy bottom. Our results show that shedding of turbulent coherent structures from ripple crests is a leading cause of ripple migration, and thereby coastal sediment transport. Additionally, within these conditions, sediment dynamics are not only controlled by bottom shear, but also by horizontal pressure gradients that can cause liquefaction of the sediment bed. Liquefaction events are rapid failure of the sediment matrix. If coastal infrastructure (pipelines, cables, platforms) are subject to liquefaction events it puts them at risk of stability failures. With respect to coastal infrastructure, results from the pipeline experiments show that turbulent coherent structures shedding from the pipeline may be the leading cause for structure scour. Overall, rresults revealed that turbulent coherent structures generated under highly transient bottom boundary layers can cause rapid bedform evolution and transport that cannot be described by conventional bottom-stress-based approaches.
On the model harbor scale, through experiments in the 3D wave-basin, our study successfully reproduced the large and persistent shallow coherent structures similar to those observed in Oarai, Japan in the aftermath of the 2011 Tohoku Tsunami. Findings better defined characteristics of flow intensity, mixing, and temporal/spatial evolution of these turbulent coherent structures.
A series of open-source numerical models were created and validated in order to simulate these coherent structures on both the boundary layer scale and the harbor scale. The numerical results complemented experimental data with high resolution of detailed flow fields that are difficult to measure. These models can be used as tools for scenario studies in the future. We successfully applied the numerical wave solver InterFoam/Waves2Foam for large-eddy simulation (LES) of breaking wave induced turbulent coherent structures in the surf and swash zones. Due to large user group of InterFoam/Wave2Foam, our demonstrated LES will encourage more researchers and engineers to adopt LES approach for their future analysis. Utilizing the OpenFOAM open-source framework, we also successfully developed a novel two-phase model for modeling sediment transport utilizing fewer assumptions than conventional single-phase approaches. All the solvers and model setup are disseminated to the public via open-source platforms, which can be easily be reproduced by other researchers. Our work will encourage other researchers to use the two-phase approach for studying sediment transport.
This project fully or partially supported 5 PhD students, 2 masters students, 1 post-doc researcher and 3 undergraduate students. Most of them are currently working as researchers, assistant professors in academic institutions, or engineers in industry. The project also produced 18 refereed journal and conference publications and PI and graduate students have given more than thirty presentation of research results in conferences, meetings and invited seminars in various research/academic institutions.
Last Modified: 01/18/2018
Modified by: Diane L Foster
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