Abstract: The phenomenon of thermoacoustic instability can cause severe vibrations, structural failure, failure of thermal protection systems, fatigue, failure of navigation and control systems, and reduced life span of engines and have even led to mission failure. Transition to thermoacoustic instability occurs when we change a system parameter such as the Reynolds number or the equivalence ratio. Traditionally, in experiments, these parameters were changed in a quasi-static manner. However, in reality, the system parameters are changed continuously. We observe rate-dependent tipping-delay in the laminar system. We find that the rate of change of parameter plays a vital role in the performance of early warning signals (EWS) for critical transitions. Further, we showed preconditioned rate induced tipping (R-tipping) in experiments and in a theoretical model of a thermoacoustic system. In another study involving an afterburner with turbulent reacting flow, under quasi-static increase in Reynolds number did not show thermoacoustic instability; in contrast, when the Reynolds number was increased at a fast rate, we observed R-tipping to thermoacoustic instability. We experimentally show a mechanism of R-tipping in thermoacoustic systems where two parameters are varying continuously. We discover that the relative rate of change of these parameters determine whether tipping will occur or not.
Biography: Prof. R. I. Sujith received his undergraduate degree in Aerospace Engineering from IIT Madras in 1988. He then graduated with an M. S. degree in 1990 and a Ph. D. in 1994, from the Georgia Institute of Technology, Atlanta, USA. He has over 360 technical publications (including 190 refereed journal publications), 12 patents and published a book on Thermoacoustic Instability. He is a recipient of the Alexander von Humboldt Fellowship and the Hans Fischer Senior Fellowship of the Institute for Advanced Study (IAS) of the Technical University of Munich. Sujith was the founding Editor-in-Chief of the International Journal of Spray and Combustion Dynamics from 2009-2015, and is currently a member of the editorial advisory board of Chaos. He has won the Young Engineer Award of the Indian National Academy of Engineering. He has been awarded the Swarnajayanti Fellowship and the J. C. Bose Fellowship by the Department of Science & Technology. He is a distinguished fellow if the International Institute of Acoustics and Vibration (IIAV) and a fellow of the Combustion Institute. He is a fellow of the Indian National Academy of Engineering and the Indian Academy of Sciences, and has been conferred the title of “TUM ambassador” of the Technical University of Munich. Prof. Sujith currently works on the application of dynamical systems and complex systems theory to study and mitigate thermoacoustic instability.