Synchronization Between the Acoustic Field of the Confinement and the Turbulent Reacting Flow

Abstract

In the previous chapter, we showed that the phenomenon of thermoacoustic instability is a result of complex interaction of various coupled nonlinear processes such as chamber acoustics, unsteady flame dynamics, and hydrodynamics present in a thermoacoustic system. Among these processes, the feedback mechanism between the acoustic field in the chamber and the heat release rate fluctuations in the flame plays a dominant role in the genesis of such thermoacoustic instability. In this feedback coupling, the heat release rate fluctuations act as a source of driving for the acoustic oscillations in a duct and also receive perturbations that are generated by acoustic oscillations. Therefore, we need to study the mutual coupling between these two processes for achieving a deeper understanding of the onset of thermoacoustic instability. In the present chapter, we will investigate the coupled interaction of the acoustic pressure and heat release rate fluctuations during the onset of thermoacoustic instability in turbulent systems, using the framework of mutual synchronization. Furthermore, we will independently present the characteristics of the forced response of self-excited acoustic pressure fluctuations and hydrodynamic fluctuations to external periodic perturbations, using the framework of forced synchronization. Such investigations may help us understand the flame-acoustic coupling in thermoacoustic systems and devise control strategies required for the mitigation of thermoacoustic instability.