Abstract
The present study is devoted to PIV investigation of vortex breakdown (VB) in swirling jets and lean premixed flames. A set of PIV experiments was carried out for submerged water and air jet flows, and also for propane/air and methane/air flames. Time-averaged and spectral characteristics of the velocity fluctuations were estimated, and properties of coherent structures (CS) were analyzed on the basis of decomposition routines. VB for the low- and high-swirl non-reacting flows is specified as spiral-type and bubble-type, respectively. In the former case, no stable RZ was present, and the vortices in the outer shear layer and near the jet axis were presumably associated with local helical instabilities. In the latter case a stable bubble-type RZ was formed, and the flow dynamics was governed by strong precession of the vortex core. The measurements for propane/air lean flame demonstrated that combustion can divert flow dynamics from these limit-cycle oscillations.
