  Interactions between a propagating hydrogen/air detonation wave and circular
water cloud are studied. Eulerian Lagrangian method involving two-way
gas-droplet coupling is applied. Different droplet (diameter, concentration)
and cloud (diameter) properties are considered. Results show that droplet size,
concentration and cloud radius have significant effects on peak pressure
trajectory of the detonation wave. Three propagation modes are identified:
perturbed propagation, leeward re-detonation, and detonation extinction.
Leeward re-detonation is analyzed from unsteady evolutions of gas and liquid
droplet quantities. The detonation is re-initiated by a local hot spot from
shock focusing of upper and lower diffracted detonations. Disintegration of
water droplets proceeds when the detonation wave crosses the cloud. In
addition, detonation extinction is featured by quickly fading peak pressure
trajectories when the detonation wave passes the larger cloud, and no local
autoignition occurs in the shock focusing area. Evolutions of thermochemical
structures from the shocked area in an extinction process are also studied. The
transfer rates of mass, energy and momentum of detonation success and failure
are analyzed. Moreover, parametric studies demonstrate that the critical cloud
size to quench a detonation decreases when the droplet concentration is
increased. However, when the droplet concentration is beyond 0.84 kg/m3, the
critical cloud size is negligibly influenced due to small droplets. Two-phase
fluid interfacial instability is observed, and the mechanism of cloud evolution
is studied with the distributions of droplet, vorticity, density / pressure
gradient magnitudes, and gas velocity.
