Numerical analysis of the mean structure of gaseous detonation with dilute water spray

Hiroaki Watanabe (1) , Akiko Matsuo (1) , Ashwin Chinnayya (2) , Ken Matsuoka (3) , Akira Kawasaki (3) , Jiro Kasahara (3)

1 Keio University [Tokyo]
2 DETO - Détonique [Institut Pprime]
3 Nagoya University

Two-dimensional (2-D) numerical simulations based on the Eulerian–Lagrangian method that take droplet break-up into account are conducted to clarify the mean structure of gaseous detonation laden with a dilute water spray. The premixed mixture is a slightly diluted stoichiometric hydrogen–oxygen mixture at low pressure. The simulated results are analysed via 2-D flow fields and statistical Favre spatiotemporal averaging techniques. Gaseous detonation with water droplets (WD) propagates stably with a velocity decrease compared with the dry Chapman–Jouguet speed. The mean structure of gaseous detonation with dilute water spray shares a similar structure as the one without water spray. However, the hydrodynamic thickness is changed due to the interaction with water spray. Overall interphase exchanges (mass, momentum and energy) that take place within the hydrodynamic thickness induce a decrease of the detonation velocity and lower the level of fluctuations downstream of the mean leading shock wave. Droplet break-up occurs downstream of the induction zone and in our case, the water vapour from the evaporation of water spray does not affect the reactivity of gaseous detonation. The laminar master equation for gaseous detonation laden with inert WD shows that the hydrodynamic thickness should rely on the gaseous sound speed, and works well as the working mixture is weakly unstable and its cellular structure is regular. The droplet flow regimes and break-up modes have also been determined. The characteristic lengths of detonation and interphase exchanges have been ordered under the present simulation conditions and have been shown to be intimately intertwined.

Mots clés: Compressible flow; Detonation waves; Multiphase and particle-laden flows; Reacting multiphase flow

Domaines: Mécanique des fluides [physics.class-ph]; Matériaux; Acoustique [physics.class-ph]; Automatique / Robotique; Electromagnétisme; Milieux fluides et réactifs; Energie électrique; Polymères; Acoustique [physics.class-ph]; Biomécanique [physics.med-ph]; Matériaux et structures en mécanique [physics.class-ph]; Thermique [physics.class-ph]; Vibrations [physics.class-ph]; Physique mathématique [math-ph]; Physique Quantique [quant-ph]

Hiroaki Watanabe, Akiko Matsuo, Ashwin Chinnayya, Ken Matsuoka, Akira Kawasaki, et al.. Numerical analysis of the mean structure of gaseous detonation with dilute water spray. Journal of Fluid Mechanics, 2020, 887, pp.A4-1. ⟨10.1017/jfm.2019.1018⟩. ⟨hal-02462140⟩