Triple Point Collision and Hot Spots in Detonations with Regular Structure

Abstract

In the present work, the details of a regular structure detonation are studied using very high-resolution two-dimensional numerical simulations. It is found that more than 300 points per half reaction length are required to resolve properly the nature of the transverse waves and the structure configuration during the collision and reflection processes of a triple point and its associated transverse wave with the channel walls. The detonation structure is found to be a double-Mach configuration, while it changes to a single-Mach configuration shortly before collision of the triple points with the wall. During the reflection, the shear layer becomes detached from the front and recedes from it, producing a pocket of partly unburned gas. After reflection, the structure is a single-Mach configuration, while it changes to a double-Mach configuration after some time. Shortly before collision, a hot spot, containing partly burned gases, is formed behind the incident wave at the vicinity of the wall. This hot spot ultimately burns by mixing of burned and unburned gases due to the existence of small-scale vortices produced by Kelvin–Helmholtz instability along the detached shear layer.

Keywords:

• Hot spot
• Kelvin–Helmholtz instability
• Mach reflection
• Transverse wave
• Triple point collision

Notes

Published as part of the Seventh Mediterranean Combustion Symposium Special Issue with Guest Editors Federico Beretta, Nevin Selçuk, Mohy S. Mansour, and Andrea D'Anna.