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We examine the multi-dimensional linear and non-linear stability of planar detonation waves for one-step Arrhenius rate with arbitrary reaction order. A normal mode analysis with an iterative shooting method is used in linear stability. Results show that the effect of decreasing the reaction order is roughly equivalent to increasing the activation energy, or decreasing the heat release and overdrive. Both the one- and two-dimensional linear stability spectra consist of a larger number of unstable modes at lower reaction order. Bifurcation to non-oscillatory modes occurs at slightly lower activation energy or higher heat release and overdrive for lower reaction order. Thus overall, a lower reaction order results in more unstable waves. Numerical simulations, using a Weighted Essentially Non-Oscillatory scheme, show that activation energy has a stronger effect on cell regularity than the reaction order. It has been suggested that a relationship may exist between transverse wavelength from multi-dimensional linear stability analysis and cell sizes. Our computations confirm previous numerical results that show that the most unstable transverse wavelengths from linear stability analysis are comparable with the minimum channel width in which one full cell is observed in numerical simulations. Wider computations show that cells, which appear regular and periodic in narrow channel computations, become irregular. The average cell size approaches a consistent limit corresponding to an even larger size. [ABSTRACT FROM AUTHOR]

Abstract: Shock-initiated ignition is studied numerically for single step Arrhenius kinetics. This is relevant to hydrogen safety, because hydrogen detonates easily, and detonation in shocked mixture may occur in deflagration to detonation transition scenarios, due to shock reflections on obstacles subsequent to flame acceleration. Simulation of ignition behind a shock moving into combustible mixture is difficult because of the singular nature of the initial conditions. The solution method includes two components. First, space as an independent variable is replaced by the ratio space over time, and second, initial conditions at a small non-zero time are used, obtained in closed form from short time asymptotics. This way, the initial singularity is effectively removed and the early process is well resolved. This method was used to study how the leading shock strength, and the heat release, affects the shock-initiated ignition process. The Essentially Non-Oscillatory algorithm used captures ignition, hot spot growth, birth of a secondary shock and transition into a detonation. Results show that for weaker shock cases as well as for higher heat release the evolution is more rapid, that a secondary shock forms closer to the contact surface and quickly becomes a detonation wave. [Copyright &y& Elsevier]

Abstract: An accidental hydrogen release in equipment enclosures may result in the presence of a detonable mixture in a confined environment. To assess the value of CFD techniques as a tool for damage assessment, numerical simulation of detonation was performed for two realistic scenarios. The first scenario starts with a pipe failure in an electrolyzer, resulting in a leak of 42g of hydrogen. The second scenario deals with a failure in a reformer where 84g of hydrogen is released. Dispersion patterns were first obtained from separate numerical simulation and detonative ignition was simulated by adding energy to a narrow region. Impulse values reached 600Ns/m2 in the electrolyzer scenario while they reached 1100Ns/m2 in the reformer. For all cases studied, the consequences are more serious in the reformer than the electrolyzer. [Copyright &y& Elsevier]