We study the initiation of the detonation in the gravitationally confined detonation (GCD) model of Type Ia supernovae (SNe Ia). In this model, ignition occurs at one or several off-center points, resulting in a burning bubble of hot ash that rises rapidly, breaks through the surface of the star, and collides at a point on the stellar surface opposite the breakout, producing a high-velocity inw...

A gaseous detonation is a combustion-driven, compressible wave propagating at supersonic speeds. Experimental visualizations and numerical simulations confirm that detonation waves have a complex, multi-dimensional, cellular structure generated by various gasdynamic interactions (Ohyagi et al. 2000; Ng and Zhang 2012). Except in special combustible mixtures (such as argon-diluted mixtures) with...

Detonation waves in gas-filled piping or tubing pose special challenges in analysis and prediction of structural response. The challenges arise due the nature of the detonation process and the role of fluid-structure interaction in determining the propagation and arrest of fractures. Over the past ten years, our laboratory has been engaged in studying this problem and developing methodologies f...

The flame born in the deep interior of a white dwarf that becomes a Type Ia supernova is subject to several instabilities, the combination of which determines the observational characteristics of the explosion. We briefly review these instabilities and discuss the length scales for which each dominates. Their cumulative effect is to accelerate the speed of the flame beyond its laminar value, bu...

* Member Technical Staff † Vice-President ‡ Professor and Chairman £ Professor Abstract Results of a recent investigation in the design of a single flow path combined cycle engine using periodic detonation waves are presented here. Four modes of operation are used in a sample SSTO trajectory in this preliminary design (sketched in Fig. [1]): (1) An ejector augmented pulsed detonation rocket for...

Computational fluid dynamics based solvers have been developed for explosion modeling in hazards analysis. These include a numerical approach to simulate flame acceleration and deflagration to detonation transition in hydrogen-air mixture and two detonation solvers. The former solves fully compressible, multidimensional, transient, reactive Navier–Stokes equations with a chemical reaction mecha...

Oxyhydrogen is a mixture of Hydrogen (H2) and Oxygen (O2) gases. Detonative mixtures of oxyhydrogens with various combinations of these two gases were used in Gas Detonation Forming (GDF) to form sheets of mild steel. In die forming experiments, three types of conical dies with apex angles of 60, 90 and 120 degrees were used. Pressure of mixtures inside the chamber before detonation was varied ...

The study on deflagration-to-detonation transition (DDT) is very important because this mechanism has relevance to safety issues in industries, where combustible premixed gases are in general use. However, the quantitative prediction of DDT is one of the major unsolved problems in combustion and detonation theory to date. In this paper, the DDT process is studied theoretically and the critical ...

Thrust from a multicycle pulse detonation engine operating at practical flight altitudes will vary with surrounding environment pressure. We have carried out the first experimental study using a detonation tube hung in a ballistic pendulum arrangement within a large pressure vessel to determine the effect that the environment has on the single-cycle impulse. Air pressure decreased below 100 kPa...

The detonation of a CHNO explosive was used for the first time to synthesize carbon nanotubes effectively at low pressure and temperature by introducing a cobalt catalyst and/or paraffin into the detonation system.