A novel fully explicit GPU-accelerated discrete element method coupled with moving particle hydrodynamics (DEM-MPH) for simulating the underwater particle sedimentation behavior

Abstract

Ensuring the safety integrity of the core catcher system during a hypothetical core disruptive accident (CDA) in a sodium fast reactor (SFR) is crucial, particularly regarding the formation of the debris bed. This study presents a novel, fully explicit Discrete Element Method (DEM) coupled with Moving Particle Hydrodynamics (MPH), accelerated on a graphics processing unit (GPU), to calculate debris bed formation with various particle sizes. The DEM approach is applied to the solid phase, while the liquid phase is calculated using the MPH method. The DEM-MPH method is explicitly updated to avoid significant differences in time steps and to efficiently accelerate calculations on the GPU.

For validation, a fundamental dam break simulation with tiny particle sizes (0.5 mm) was conducted. The simulation results show good agreement with experimental data in terms of the angle of repose and spread length. Additionally, the GPU-accelerated calculations demonstrated a calculation efficiency of several hundred times improvement compared to a single CPU.

The DEM-MPH method was also compared to a previous experiment conducted by Sun Yat-Sen University, demonstrating the capability of handling almost 10 million particles. The results indicate that particle size significantly impacts debris bed formation. As particle size decreases, the debris bed shape becomes flatter due to the more significant convection within the liquid pool and the drag force between the solid phase and the liquid. All calculations showed agreement with experimental results regarding debris bed height. Overall, the present DEM-MPH method shows great potential for understanding debris bed formation, which is indispensable for ensuring SFR safety.