CaltechTHESIS
  A Caltech Library Service

A numerical and analytical study of detonation diffraction

Citation

Arienti, Marco (2003) A numerical and analytical study of detonation diffraction. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-02122003-152525

Abstract

An investigation of detonation diffraction through an abrupt area change has been carried out via two-dimensional, parallel simulations. The existence of critical conditions for successful diffraction is closely related to the occurrence of localized re-initiation mechanisms, and is relevant to propulsion and safety concepts concerning detonation transmission. Our analysis is specialized to a reactive mixture with perfect gas equation of state and a single-step reaction in the Arrhenius form. The concept of shock decoupling from the reaction zone is the simplest idea used to explain the behavior of a diffracting detonation front. Lagrangian particles are injected into the flow in order to identify the dominant terms in the equation that describes the temperature rate of change of a fluid element, expressed in a shock-based reference system. Conveniently simplified, this equation provides an insight into the competition between the energy release rate and the expansion rate behind the diffracting front. We also examine the mechanism of spontaneous generation of transverse waves along the front. This mechanism is related to the sensitivity of the reaction rate to temperature, and it is investigated in the form of a parametric study for the activation energy. We study in detail three highly resolved cases of detonation diffraction that illustrate different types of behavior, super-, sub-, and near-critical diffraction. We review the applicability of existing shock dynamics models to the corner-turning problem. Numerical results from the parametric study are compared with predictions from these theories in the attempt to find a formula for shock decay in a quenching detonation. This estimate is then used in the simplified temperature rate of change equation to provide a relation between critical channel width and activation energy. We conclude this study by examining the spontaneous formation of transverse waves along the wavefront of a successfully transmitted detonation. The problem is simplified to a planar CJ detonation moving in a channel over a small obstacle to investigate how acoustic waves propagate within the reaction zone. Depending on the reaction kinetics, we show that such waves may be amplified due to feedback between the chemical reaction and fluid motion. The amplification can lead to shock steepening and formation of transverse detonation waves.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:acoustic theory; critical diameter; detonation shock dynamics; direct numerical simulation; high-performance simulation; parallel computing; particle analysis; reactive flow; Skew's construction; unsteady flow; Whitham's shock dynamics; ZND detonation
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Shepherd, Joseph E.
Thesis Committee:
  • Hornung, Hans G. (chair)
  • Meiron, Daniel I.
  • Cohen, Donald S.
  • Shepherd, Joseph E.
  • Colonius, Timothy E.
Defense Date:9 December 2002
Author Email:arienti (AT) galcit.caltech.edu
Record Number:CaltechETD:etd-02122003-152525
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-02122003-152525
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:610
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:18 Feb 2003
Last Modified:26 Dec 2012 02:30

Thesis Files

[img]
Preview
PDF (arienti_PhD_thesis.pdf) - Final Version
See Usage Policy.

45Mb

Repository Staff Only: item control page