Some Specific Characteristics of Turbulence in the Reactive Wakes of Bluff Bodies

The results of a detailed experimental analysis of the e ows associated with bluff-body stabilized premixed combustion are presented. The experimental setup has been designed to facilitate as much as possible the test of numerical predictions of such a e ow geometry. The boundary conditions are well dee ned and easy to reproduce from a numerical point of view. The results reported here are based principally on velocity measurements using a four-beam two-color laser Doppler velocimeter. As far as the mean structure of the wakes is concerned and cone rming in that respect the results reported in the literature, it is shown that the presence of combustion leads only to quantitative changes of the mean structure of the reactive wakes when compared with their inert counterparts. This is no longer the case when the statistical and spectral properties of the wakes are considered. Indeed,a completerestructuring oftheinstantaneouse owstructureinducedbydramaticchangesofthelarge-scale motionpropertiesisobserved when combustion is developing inthewake. Thereacting wakesarecharacterized by theabsence of thevortex shedding observed in inert wakes, butdepending on the equivalence ratio of theincoming mixture, a longitudinal pulsation associated with the symmetric e apping of the e ame fronts anchored at the e ame holder edges can be observed.