Detecting the Onset of an Impending Thermoacoustic Instability Using Complex Networks

Abstract

Recently, M. Murugesan and R. I. Sujith (“Combustion Noise is Scale-Free: Transition from Scale-Free to Order at the Onset of Thermoacoustic Instability,” Journal of Fluid Mechanics, Vol. 32, June 2015, pp. 225–245) showed that the transition from combustion noise to thermoacoustic instability can be represented as a change from a scale-free to a regular structure in the topology of complex networks. These topological changes of the complex networks during this transition can be quantified by calculating the network properties. In this paper, the variation of network properties, namely, clustering coefficient, characteristic path length, network diameter, and global efficiency is presented as the system dynamics undergoes transition from combustion noise to thermoacoustic instability. These network properties capture the change in system dynamics well before the rise in pressure amplitude levels in the combustors. These network properties can be used as early warning signals to detect the onset of impending thermoacoustic instabilities.