The objectives of this project were: (i) to develop a model for underwater munitions' mobility and burial (UnMUMB), (ii) to use SERDP field experimental data to explore seafloor environment characteristics such as liquefaction, sand wave migration and deep scour, (iii) to develop new methodology for deep scour burial, (iv) to use Delft3D to predict complex seafloor environment, (v) to develop a coupled Delft3D and wave induced liquefaction model to predict sandy seafloor morphological change, (vi) to develop a coupled Delft3D-UnMUMB model to predict underwater munitions’ mobility and burial as well as the change of the environment, and (vii) to provide the model formulations with User’s Guide to SERDP investigators such as to whom working on a more sophisticated Underwater Munitions Expert System (UnMES) as well as to the larger SERDP, Department of Defense (DoD), coastal engineering, and scientific communities.

The project team developed UnMUMB model (Chu 2020, 2022) on the base of the principal investigator's (PI) earlier efforts on establishing a 6-DoF model to predict three-dimensional trajectory of sea-mine through air, water, and sediment (Chu et al., 2004, 2005; Chu and Fan 2005, 2006, 2007; Chu 2009; Donas et al. 2021) for the Office of Naval Research accelerated research initiative “Mine Burial Prediction” during 2001-2005 (Bennett, 2000). This model contains full physics including nonlinear dynamics, fluid-structure interaction, instability theory (Chu and Fan 2005), and bearing factor method to calculate the sediment force and torque with cavities for mine movements in sediment (Chu and Fan 2007).

The project team collaborated with SERDP funded efforts including MR-2319 “Continuous Monitoring of Mobility, Burial and Re-Exposure of Underwater Munitions in Energetic Near-Shore Environments”, MR-2320 “Long Time Series Measurements of Munitions Mobility in the Wave- Current Boundary Layer”, and MR19-1317 “Towards Developing Demonstrations for Munitions Mobility and Burial in the Underwater Environment” to get sufficient and reliable data in both seabed environment and munitions’ mobility/burial and MR19-1126 “Advanced Capabilities in the Underwater Munitions Expert System” to incorporate our effort into the UnMES. We also obtained, identified and compiled through searches of academic journals, thesis and dissertation databases, DoD and National Oceanic and Atmospheric Administration reports, interlibrary loan, and the internet.

Results were provided to the larger community via six peer-reviewed journal articles: Chu et al. (2022), which concentrated on development and verification of the UnMUMB model, Pessanha et al. (2022), which focused on sediment accretion in lower-energetic region, Pessanha et al. (2023a), which fixated on the wave-induced liquefaction, Passanha et al. (2023b), which focused on the sand wave migration, Gough et al. (2022), which established a new method for deep scour by an energetic wave event, Chu et al. (2021), which concentrated on development and verification of the coupled Delft3D-UnMUMB model. In addition, the User’s Guide for the Coupled Delft3D-UnMUMB model was published at the website: https://apps.dtic.mil/sti/citations/AD1173688.

The UnMUMB model uses the 6-DoF moment of momentum equation to predict underwater munitions' burial and mobility with various object parameters and initial conditions. The mobility is predicted by equation and the burial is forecasted by equation. Delft3D output provides the environmental parameters around the munition, which are required by the UnMUMB model for predicting the munition’s burial and mobility. The capability of the coupled Delft3D-UnMUMB model was vilified using environmental conditions and spanning a range of object parameters reported in a separate study (MR-2320).

Future work should explore the role to determine the threshold for mobility with objects near to or less dense than water-saturated sand tended to migrate, and denser objects tended to bury; and to identify munition's migration distance under energetic wave and current forcing in environment with bathymetric constrained and with no bathymetric constrained. Besides, for operational use in the real world, the geometrical characteristics of objects need to be upgraded to include various shapes fitting the real munitions.

References:

Bennett, R.H., 2000: Mine Burial Prediction Workshop Report and Recommendations, Final Report prepared for ONR Dr. R.H. Wilkens, Dr. J. H. Kravitz, and Dr. D. G. Toderoff, Seaprobe, Inc., Technical Report Number SI-0000-02, pp 21.

Chu, P.C., 2009: Mine impact burial prediction from one to three dimensions. Applied Mechanics Review, 62, no. 1, 010802, 1-25.

Chu, P.C., C.W. Fan, A.D. Evans, & A.F. Gilles, 2004: Triple coordinate transforms for prediction of falling cylinder through the water column. Journal of Applied Mechanics, 71, 292-298.

Chu, P.C., A.F. Gilles, & C.W. Fan, 2005: Experiment of falling cylinder through the water column. Experimental and Thermal Fluid Sciences, 29, 555–568.

Chu, P.C., & C.W. Fan, 2005: Pseudo-cylinder parameterization for mine impact burial prediction. Journal of Fluids Engineering, 127, 1,515-1,520.

Chu, P.C., & C.W. Fan, 2006: Prediction of falling cylinder through air-water-sediment columns.Journal of Applied Mechanics, 73, 300-314.

Chu, P.C., & C.W. Fan, 2007: Mine impact burial model (IMPACT35) verification and improvement using sediment bearing factor method. IEEE Journal of Oceanic Engineering, 32, 34-48.

Chu, P.C., V.S. Pessanha, C.W. Fan, & J. Calantoni, 2021: Coupled Delft3D-object model to predict mobility of munition on sandy seafloor. Fluids, 6 (9), 330, https://doi.org/10.3390/fluids6090330.

Chu, P.C., & C.W. Fan, 2022: User Guide – Coupled Delft3D-Underwater Munition Scour Burial Model, SERDP MR19-C1-1073,1-70, https://apps.dtic.mil/sti/trecms/pdf/AD1173688.pdf

Donas, A., I. Famelis, P.C. Chu, & G. Galanis, 2021: Optimization of the Navy’s three- dimensional mine impact burial prediction simulation model, IMPACT35, using high-order numerical models. Journal of Defense Modeling and Simulation: Application, Methodology, Technology 1-15, doi: 10.1177/154851292129211028661.

Gough, M.K., P.C. Chu, V.S. Pessanha, & J. Calantoni, 2022: Deep burial of a tapered cylinder by an energetic wave event. IEEE Journal of Oceanic Engineering, 47, IEEE Xplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=9976217

Pessanha, V.S., P.C. Chu, & M.K. Gough, 2022: Sediment accretion in a lower-energetic location during two consecutive cold fronts. Journal of Operational Oceanography, http://doi.org/10.1080/1755876X.2022.2100145

Pessanha, V.S., P.C. Chu, M.K., Gough, and M.M. Orescanin, 2023a: Coupled model to predict wave-induced liquefaction and morphological changes. Journal of Sea Research, 192, https://www.sciencedirect.com/science/article/pii/S1385110123000187?via%3Di hub.

Pessanha, V.S., P.C. Chu, M.K., Gough, and M.M. Orescanin, 2023b: Sand wave migration near the southeastern corner of Martha’s Vineyard, Massachusetts, USA. International Journal of Sediment Research, 38, https://doi.org/10.1016/j.ijsrc.2023.04.006