Novel Eulerian Two-phase Simulations for Burial Dynamics of Munitions
Dr. Tian-Jian Hsu | University of Delaware
The project team will work on a novel numerical modeling approach to simulate the scour burial dynamics of munitions in underwater environments based on an Eulerian two-phase flow modeling framework called SedFoam. The 1-year proof-of-concept study will create a high fidelity multi-phase numerical modeling framework to complete the understanding of the physics driving previously observed extreme burial in underwater environments. The project team will evaluate the model’s capability in simulating general scour burial processes and particularly for liquefaction, bed failure and slumping of the sediment bed, which has been attributed as a key process driving rapid munitions burial. The project team will also evaluate SedFoam to simulate Strategic Environmental Research and Development Program (SERDP)-supported field observations of munitions scour burial. The work may be summarized into the following three objectives.
- Develop an effective sub-model for simulating grain-scale coupling between dilatancy and pore pressure feedback in SedFoam.
- Validate newly enhanced SedFoam with a series of existing laboratory experiments for liquefaction and slumping.
- Carry out proof-of-concept simulations of laboratory and field conditions for munitions burial previously observed by SERDP-funded investigators.
SedFoam is a unique modeling methodology compared to other numerical models for sediment transport. SedFoam resolves the full dynamics of sediment transport without the need to artificially separate transport into bedload and suspended load. Moreover, SedFoam simulates the particle phase and its interaction with the fluid phase using a continuum description by averaging the behavior of particles and providing closures for intergranular interactions. Therefore, SedFoam is among the most computationally efficient two-phase modeling frameworks and it becomes possible to use SedFoam to simulate meter-scale burial dynamics, which covers almost the full range of calibers of interest (from 25 millimeters [mm] up to about 155 mm). The project team will establish a preliminary simulation framework based on SedFoam to simulate burial of underwater munitions. A key capability necessary to achieve the objective model “pore-pressure feedback”. Pore-pressure feedback represents a grain-scale coupling between dilatancy and compaction driven by the pore pressure gradient and it has been shown to be responsible for the dynamics of slumping during landslides. Here, the project team hypothesize that pore-pressure feedback is the key to performing realistic simulations of scour burial of munitions during liquefaction and bed failure. Using the newly enhanced SedFoam, they will carry out simulations of SERDP-supported observational studies where rapid burial of surrogate munitions was believed to be triggered by joint effects of liquefaction and momentary bed failure.
The 1-year effort will evaluate how pore-pressure feedback mechanisms in liquefaction, momentary bed failure, and slumping of sediments may lead to rapid burial of munitions. Additionally, the project team will provide proof-of-concept simulations using existing laboratory and field observations. They foresee the creation of a robust simulation tool that may be utilized to study a wide range of scenarios; the simulation results may be utilized in the future to provide training data for an existing expert system to predict burial dynamics during liquefaction and momentary bed failure conditions believed responsible for observed extreme burial of munitions during storm events.