Long Time Series Measurements of Munitions Mobility in the Wave-Current Boundary Layer
Dr. Joseph Calantoni | U.S. Naval Research Laboratory
The project objective is to provide detailed time series measurements of the in situ boundary layer processes responsible for munitions mobility including transport, burial, and excavation. The researchers will perform a set of field experiments to characterize the environment in which munitions are found while simultaneously recording the location of munitions relative to the seafloor at high spatial and temporal frequency. Unlike previous investigations that have provided before and after snapshots of munitions mobility, this instrumentation is capable of providing high spatial and temporal resolution measurements for the relevant boundary layer processes (e.g., wave height and direction, current profiles, suspended sediment concentrations, and sediment erosion and deposition) while simultaneously monitoring the mobility of surrogate munitions. The researchers hypothesize that the likelihood of mobility is not equal for all munitions and may be primarily quantified by as few as two non-dimensional parameters. The researchers will deploy an appropriate range of surrogate munitions to test this hypothesis.
The technical approach includes detailed field measurements of munitions mobility and the simultaneous environmental conditions driving mobility. Using sector scanning and pencil beam sonars, the researchers will continuously monitor the mobility of munitions while simultaneously measuring time series data of the boundary layer hydrodynamics and sediment transport. Additionally, underwater video cameras will be used to track mobility at the more energetic field site in year two. Instruments will be mounted on a pair of large rugged frames that will be deployed in different water depths at a pair of sandy field sites. The researchers are unaware of any existing field data sets that include similar temporal resolution of munitions mobility coupled with detailed measurements of the relevant boundary layer dynamics over continuous study periods of four to five weeks.
The investigations expect to provide answers to fundamental questions about the fate of munitions that should be important to site remediation and management such as:
- Can groups of munitions be classified as having relatively high or low likelihood of mobility?
- Do groups of munitions exist that are more likely to be detected after energetic flow conditions (e.g., storms generating large gradients in sediment transport)?
- Does a simple function of munitions characteristics (e.g., bulk density and size) exist that may be used to estimate the likely location of munitions relative to the bottom (i.e., from proud to some finite depth of burial)?
- Do groups of munitions exist that have a high likelihood to be permanently buried regardless of site characteristics and changing environmental conditions?
Additionally, the measurements will provide a baseline data set that process based models for prediction of munitions mobility (e.g., Vortex Lattice UXO Mobility Model) may utilize for verification and validation. (Anticipated Project Completion - 2015)