NEESR: Tsunami Induced Coherent Structures and their Impact on our Coastal Infrastructure

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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.