Spatio-temporal Linear Stability Analysis of Reacting Wake Systems*

Large scale coherent flow structures, ensuing from the hydrodynamic stability characteristics, play a controlling role in several combustion phenomena, such as combustion instability, mixing and entrainment and blowoff. Hydrodynamic stability characteristics of multi-bluff body systems is significantly different in comparison with that of single bluff body systems. The confined wake system, through the method of images, represents an infinite wake system with an imposed symmetry (sinuous or varicose) at the wake-wake interface. The objective of the work is to compare the stability characteristics of the infinite-wake system with the confined wake system. Presence of an additional element destabilizes the system. The stability characteristics of the multi-wake system converge onto the behavior of the confined wake system in the asymptotic limit of infinite wake system. Further, the study utilizes the resonant wave interaction[Juniper, J. Fluid Mech., 565, 171-195 (2006)] as a theoretical model to predict the behavior of the multi-wake systems. The model predicts the critical L/D, which correspond to the maximum destabilization of the multi-wake system, accurately for parametric ranges when the system is absolutely stable.