An attempt to simulate multilayer particle resuspension in a cavity

The present work deals with particle re-entrainment from a multilayer deposit exposed to a sudden flow increase. An early model is suggested to simulate the multilayer remobilisation of solid aerosol particles. The work is decomposed in two parts: 1. an algorithm is first developed for the virtual reconstruction of the multilayer deposit given its porosity and 2. particle detachment off the deposit is coupled with computational fluid mechanics. Experimental observations have shown that the clustering effect plays an important role in multilayer resuspension. Particle aggregates, and not individual particles, tend to reenter the turbulent flow. A cluster identification procedure is therefore suggested to work out resuspendable particle clusters. The condition of cluster dislocation is based on a force-balance model. The cluster detachment off the multilayer deposit occurs whenever the aerodynamic force overcomes the adhesive force. The turbulent flow was computed with a large eddy simulation. The numerical results showed satisfactory agreement with experimental data. Findings from that study showed that the wall shear stress is a main resuspension agent. Results have a direct impact for the safety assessment of gas-cooled high temperature reactor, in which the remobilisation of radioactive graphite particles occurs.