Vortex Lattice UXO Mobility Model Integration
Knowledge of the processes and time scales for the scour, burial, re-exposure, migration, and subsequent reburial of unexploded ordnance (UXO) that remain in and on the seafloor in coastal environments is key to planning the future use of these sites, including possible remediation. Because these processes are intrinsically nonlinear and chaotic, predictions of the fate and transport of a broad-field UXO population are extremely sensitive to the initial state of that population. Specifically, the numbers of UXO per cubic meter of seabed sediments, the distribution in the depth of impact burial, and the horizontal dispersion of the UXO population are critical input parameters.
The objective of this project is to integrate an existing ballistics impact burial model with the Vortex Lattice UXO Mobility Model (UXO-MM) in order to compute the initial state of the UXO population based on range firing records at various sites.
The UXO-MM is a physics-based model that solves a classic boundary value problem using computational fluid dynamics methodologies. The UXO-MM applies long-term fluid forcing by wind, waves, and currents to the sediment budget of an underwater UXO site to predict changes in the initial burial state of the resident UXO population. It conducts a sequence of time-stepped computations of UXO exposure and subsequent mobility until local scour processes and broad-scale accretion induce reburial. ESTCP has formally validated the UXO-MM at coastal sites representative of three of the four primary coastal types populated by UXO. The ballistic impact burial model to be embedded into the UXO-MM architecture is STRIKE35, a six-degree-of-freedom ballistics model that is a derivative of the Navy's well-proven mine impact burial model, IMPACT35.
The project team will integrate a ballistics impact model with the UXO-MM and demonstrate and validate the integrated UXO Impact/Mobility Model (UXO-IMM) at a firing range having adequate site attributes, including digital bathymetry; long-term wind, wave, current, and water level data; detailed firing records; and ground-truth UXO survey data. The team will provide results of UXO-IMM simulations resulting from parameter sweeps of forcing conditions in specified geomorphological settings to assist with the development of the Underwater Munitions Expert System (UnMES) being developed under SERDP project MR-2227. The integrated UXO-IMM and UnMES will combine both modeling approaches, thereby functioning as a repository for the inferred relationships, including rule-of-thumb insights that will organize state-of-the-art knowledge into predictions of UXO burial and mobility in data-sparse environments.
The integrated UXO-MMs can be used to develop initial wide area assessments that subdivide a UXO field into stable and unstable areas, thereby avoiding unproductive deployment of detection resources in areas where UXO remain a non-factor beneath a stable seabed. This predictive capability enables survey efforts or remediation efforts to be scheduled with respect to making a determination of how long UXO will remain where they are found. The UXO-IMM can be used to conduct an analysis of the risk and cost impact of UXO at a coastal site. The models can determine (and minimize) the scope of any required remediation efforts, minimize both survey and removal efforts, and thus realize potential savings of millions of dollars. The models also can ensure that any remediation effort covers enough distance from protected sites so that UXO will not move back into areas of concern, thereby avoiding recurring cleanup efforts. (Anticipated Project Completion - 2014)
Points of Contact
Dr. Gerald D'Spain
Scripps Institution of Oceanography
SERDP and ESTCP
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