Detonation waves are self-sustained supersonic combustion waves [1]. These waves areled by a
shock which compresses the fresh reactive media to a much higher temperatureand pressure for
rapid reaction [1]. The tremendous reaction heat release occurring behindthe shock in return
energizes the propagation process. As such this closely coupledshock-reaction complex
self-sustains. Detonation waves can be sustained in a variety ofenergetic media including
reactive gases. The large overpressures generated behind gaseousdetonations make them
attractive and useful for developing propulsion systems [2] suchas rotating detonation engines
(RDEs) [3 4] and pulse detonation engines (PDEs) [5 6].These applications require reliable
control of the accurate ignition and stable propagationof a detonation wave. Likewise for
safety applications [7 8] it is also desirable to have thepredictability for the eventual
initiation of a detonation wave and for its propagation limitswhen different mitigation
strategies are used [9]. Therefore realizing all these practicalpurposes requires predictive
capability of detonation behavior.Detonations in gases usually propagate with lateral strain.
For example in confinedgeometries of small size such as narrow channels or tubes detonations
are subject tosignificant losses induced by boundary layers which act as a mass sink and
result in flowdivergence in reaction zones thereby giving rise to lateral strain impacting the
detonationpropagation [10] while in geometries of varying cross-section areas or curved
channels astypically seen in PDE pre-detonator tubes and RDE combustors detonations are
curvedwith the flow also diverging after passing the leading front [11-13]. These lateral
strainrates are generally known to decrease the detonation speed and its propagation limit [10
11 13-17]. Thus in order to achieve the practical purposes of either utilizing or
avoidingdetonations the effect of such lateral strain rates on detonation dynamics e.g.
detonationpropagation speed and its failure limit needs to be quantified for revealing their
influencingmechanism. This however is still poorly understood and not well treated since the
highlyunsteady nature of the well-known multi-dimensional structures of detonations
greatlycomplicate the efforts.
