Evolution of detonation formation initiated by a spatially distributed, transient energy source

Abstract

Detonations usually form through either direct initiation or deflagration-to-detonation transition (DDT). In this work, a detonation initiation process is introduced that shows attributes from each of these two processes. Energy is deposited into a finite volume of fluid in an amount of time that is similar to the acoustic time scale of the heated fluid volume. Two-dimensional simulations of the reactive Euler equations are used to solve for the evolving detonation initiation process. The results show behaviour similar to both direct initiation and DDT. Localized reaction transients are shown to be intimately related to the appearance of a detonation. Thermomechanical concepts are used to provide physical interpretations of the computational results in terms of the interaction between compressibility phenomena on the acoustic time scale and localized, spatially resolved, chemical energy addition on a heat-addition time scale.

The role of multidimensional instabilities in direct initiation of gaseous detonations in free space

“…Following Regele et al (2016), we ignite the detonation using the concept of thermodynamic analysis of direct initiation and deflagration-to-detonation transition (DDT) by Kassoy (2016). A hot spot with p s = (γ − 1)E s and T s = 20.0 for x 1 in 1D and (x − 1000) 2 + (y − 1000) 2 1 in 2D is adopted.…”

“…The amount of energy added to the hot spot is large enough to make the thermal power deposition from a point source into the heated volume on a time scale that is smaller than the characteristic acoustic time scale. Strong blast waves therefore can be initiated by the hot spot (Kassoy 2016;Regele et al 2016). Compared with initiation using a point blast wave with constant initial density, this alternative approach allows us to use a larger time step and, hence, to reduce drastically the wall-clock time of each simulation without affecting the the flow features we are interested in.…”

Wavelet Methods and Adaptive Grids in One-Dimensional Movable Boundary Problems

“…Regele et al [6,7] proposed a simple and robust method for computation of shock waves based on AWCM, which is absolutely different from all the former studies because it uses not only wavelets to trace shock waves or generate adaptive grids but also to control artificial viscosity to restrain numerical oscillations. In recent years, the method had been applied to simulate combustions, initiations, and detonations successfully [7][8][9].…”

Hotspot characterization and detonation initiation in thermally stratified reactive mixtures

“…In 2 dimensions similar observations as in 1D simulations could be made. Most recently Regele et al [51] were also able to show that for energy deposited into a fluid volume on an acoustic timescale similar behavior for direct detonation initiation and DDT can be observed. Further it was shown that the investigated detonation initiation process under the conditions at hand were essentially independent from viscous and diffusive effects.…”

“…As performed in Regele et al [51] the local acoustic to heating timescale ratio of a moving wave can be evaluated to further investigate the different ignition dynamics. Since the excitation time can be assumed to be much smaller than the induction time τ e τ i , the heat release throughout a small fluid volume of length ∆x at x 0 can be assumed to occur between τ i (x 0 ) and τ i (x 0 + ∆x).…”