Browsing by Author "Gross, Benedict M."
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Item Mobility of unexploded ordnance using spherical surrogates in the swash zone(University of Delaware, 2019) Gross, Benedict M.Predictive and probabilistic models require physical data to implement a practical procedure for monitoring and removing munitions or unexploded ordnance (UXO). Physical UXO response to wave forcing varies depending on the shape, location and density of a given munition. A laboratory experiment was conducted to study the mobility of spherical munition surrogates for cluster bombs (BLU61). ☐ A dam-break mechanism was designed in the Center for Applied Coastal Research wave flume, generating repeatable swash events onto a mobile sand bed with median grain diameter of 0.31 mm and a slope of 1:7. A variety of sensors were deployed in the flume to monitor the produced hydrodynamics including a maximum water velocity ~ 1.5 m/s. A Velodyne laser system was used to monitor bed surface variability. A wide-angle field of view camera was deployed from overhead to track surrogate response in the form of displacement. ☐ Four spherical munition surrogates were constructed to span a range of densities (specific gravity between 1.8 and 7.7). Surrogates were deployed in pairs at five different locations on the beach and at three different burial depths. Each scenario was repeated five times to determine a probabilistic response to repeatable forcing, determined by sensor data comparison for all runs. The beach was reshaped manually between subsequent runs, and a root-mean-square elevation error of less than 3 mm was maintained. Imagery from the overhead camera was converted to real world coordinates through a camera calibration and rectification. Cross-shore surrogate trajectories were traced using a motion-based object tracking technique and validated through manual measurements. ☐ A relationship between wave forcing, initial sphere location, initial burial depth and sphere density to sphere response (subsequent migration) was formed through parameterization and a dimensional analysis. An Object Mobility Number was identified for and compared to the total distance traveled determined from averaging five cross-shore trajectories (squared correlation coefficient of 0.65). Calculated mobility numbers increased with a decrease in density. Total travel distance decreased with an increased initial burial depth. Net onshore motion was not observed for any of the tested scenarios. Motion initiated upon uprush or backwash always resulted in a net offshore displacement.Item Momentum Balance Analysis of Spherical Objects and Long-Term Field Observations of Unexploded Ordnance (UXO) in the Swash Zone(Journal of Marine Science and Engineering, 2023-01-03) Cristaudo, Demetra; Gross, Benedict M.; Puleo, Jack A.Military activity has resulted in unexploded ordnance (UXO) existing in the nearshore. Understanding and predicting UXO behavior is important for object identification, and management. Here, two studies (laboratory and fieldwork) have been conducted to observe UXO surrogates in the swash zone and relate burial and migration to the underlying forcing conditions. A small-scale laboratory dam-break study was conducted to quantify migration of varying density spherical objects at different locations on a sloping, mobile, sandy bed. A moment balance was applied to derive two data-driven relationships to: (1) predict moments from the cross-shore flow velocity with predictions confined within a factor of two; (2) predict upslope or downslope migration from the moment. Fitting coefficients for the upslope and downslope relationships vary as a function of density, initial position, and burial. A field study was also conducted to investigate long-term behavior of eight varieties of UXO surrogates. Of the 129 observations, 56% were mobilized of which 76% were directed offshore. Burial/exposure was mostly related to far-field beach accretion/erosion (67%). However, scouring processes were also observed. Data showed that migration is likely a short-term process and most munitions will ultimately scour into a mobile bed.