Triple Point Collision and Origin of Unburned Gas Pockets in Irregular Detonations

TL;DR

This study uses high-resolution simulations to analyze the collision dynamics of triple points in irregular detonations, revealing mechanisms behind unburned gas pocket formation and detonation re-initiation.

Contribution

It provides detailed insights into the collision and reflection processes of triple points and their role in unburned gas pocket formation in irregular detonations.

Findings

Triple point-wall collision interacts with unreacted pockets.

Reflection leads to double Mach configuration stability.

Unburned pockets contribute to detonation re-initiation mechanisms.

Abstract

The turbulent structure of an irregular detonation is studied through very high resolution numerical simulations of 600 points per half reaction length. The aim is to explore the nature of the transverse waves during the collision and reflection processes of the triple point with the channel walls. Consequently the formation and consumption mechanism of unreacted gas pockets is studied. Results show that as the triple point collides with the wall, the transverse shock interacts with the unreacted pocket. After reflection of the triple point off the wall, the transverse wave interacts with the wall. The structure found to be of a double Mach configuration and does not change before and after reflection. In the second half of the detonation cell the triple point and the transverse wave collide simultaneously with the wall. The strong transverse wave switches from a primary triple point before collision to a new one after reflection. After some time a weak triple point reflects off the wall and hence the structure exhibits more like a single Mach configuration. Due to simultaneous interaction of the triple point and the transverse wave with the wall in the second half of the detonation cell, a larger high pressurized region appears on the wall. During the reflection the reaction zone detaches from the shock front and produces a pocket of unburned gas. Three mechanisms found to be of significance in the re initiation mechanism of detonation at the end of the detonation cell; i: energy resealed via consumption of unburned pockets by turbulent mixing ii: compression waves arise due to collision of the triple point on the wall which helps the shock to jump abruptly to an overdriven detonation iii: drastic growth of the Richtmyer Meshkov instability causing a part of the front to accelerate with respect to the neighboring portions.