Particle-resolved simulation of randomly packed pebble beds with a novel fluid-solid coupling method

Abstract

The Helium Cooled Pebble Bed (HCPB) is a common type of fusion reactor. An in-depth understanding of the helium flow behaviors in the interstitial void space between pebbles and the influence of hydrodynamics on the efficiency of purging tritium is important for the better design of the tritium breeding blanket. Particle-resolved simulation strategy has been widely used to model the HCPB system but generally suffers a tedious mesh generation process due to the complex geometries. To overcome this difficulty, this study develops a novel fluid-solid coupling strategy, p-IBM, which combines the porosity-based mesh adaption and the immersed boundary method. A small pebble bed consisting of 158 particles is first simulated with this method and good agreement with the traditional particle-resolved simulation using body-fitted grids is achieved. The proposed p-IBM method is then applied to simulate a larger pebble bed containing 3190 particles, where boundary wall effects on key parameters such as the pressure drop, fluid channeling and purging process of tritium are evaluated and discussed.