A numerical analysis on hydrodynamic deformation of molten droplets in a water pool

Motivated by basic understanding on the single-droplet steam explosion phenomenon, the present study is concerned with the simulation of the molten droplet preconditioning (deformation/pre-fragmentation) during the initial phase of the fuel coolant interaction (FCI) by using the CFD code FLUENT through the Volume of Fluid (VOF) method. Due to the complexity of the problem, only the hydrodynamics of the multiphase system, without heat transfer, is considered. Calculations were performed for various configurations (melt–coolant two-phase system, and melt–coolant–vapor three-phase system) demonstrating that the current approach is capable of capturing the interfaces between the phases (melt, water and vapor) and predicting the droplet behavior with a reasonable mass conservation. A melt droplet disturbed by an external trigger is also analyzed, as well as the effect of the pressure pulse magnitude on the severity of droplet deformation. The MISTEE experimental data was used as a benchmark for the validation of the performed calculations. The results of the separate-effect study quantitatively demonstrate the importance of droplet velocity and melt properties on the melt droplet preconditioning.

► Hydrodynamic deformation of a molten droplet in coolant is simulated numerically.
► The deformation rate increases with relative velocity and pressure pulse.
► The droplet with lower density and higher surface tension is resilient to deformation.