PROPAGATION VELOCITY OF INERTIAL WAVES IN CYLINDRICAL SWIRLING FLOW

Inertial waves are observed in swirl burners, due to the acoustic waves crossing the swirl generators. These waves can significantly modify the flame response in terms of flame transfer function because the propagation mechanisms are different for acoustic and inertial waves. Acoustic waves propagate at the speed of sound, whereas inertial waves travel with convection. Small changes in burner configuration may convert the constructive superposition of flame responses to a destructive one, or vice versa, which may change the flame transfer function. Therefore, it is necessary to identify the propagation mechanisms correctly. The aim of this paper is to re-examine the assumption that inertial waves travel with convection. An analytical approach is combined with numerical simulations to determine and validate the propagation speed with emphasis on the impact of different swirl strengths.