# R. I. Sujith

Sujith Raman Pillai Indusekharan Nair (popularly known as R. I. Sujith) is an Institute Professor and the D. Srinivasan Chair Professor in the Department of Aerospace Engineering at the Indian Institute of Technology Madras. In 2023, he was inducted as International Member of the United States National Academy of Engineering. He was selected as a Fellow of the Combustion Institute in 2022, and was awarded the Distinguished Fellowship of the International Institute of Acoustics and Vibration in 2021. He received the J. C. Bose Fellowship in 2019 and the Swarnajayanti Fellowship in 2005 from the Department of Science and Technology of the Government of India. He is a Fellow of the Indian Academy of Sciences, an Associate Fellow of the American Institute of Aeronautics and Astronautics, a Fellow of the Indian National Academy of Engineering, and an Honorary Fellow of the Indian Society of Systems for Science and Engineering (ISSE). He has been awarded Hans Fischer Senior Fellowship from the TUM Institute for Advanced Study in 2010. He was awarded Alexander von Humboldt Fellowship in 2000. He was the editor-in-chief of the International Journal of Spray and Combustion Dynamics from 2009 to 2015. He is currently a member of the editorial advisory board member of Chaos: An Interdisciplinary Journal of Nonlinear Science.

## Early life

Sujith was born on May 11th, 1967, in Thiruvananthapuram, Kerala, India. He completed his B. Tech. in Aerospace Engineering from the Indian Institute of Technology Madras, where he received the HAL prize for securing First Rank in his Department. He earned his Ph.D. in Aerospace Engineering on "Behavior of Droplets in Axial Acoustic Fields" working with the legendary Ben T. Zinn at Georgia Institute of Technology, from 1990-1994 and graduating as the “Top Graduate Student from the College of Engineering”. Subsequently, he worked as a Postdoctoral Fellow in the same department from 1994-1995, where he worked in the area of combustion in microgravity and Laser Doppler Velocimetry. He then joined his alma mater, the Indian Institute of Technology Madras, as a Lecturer in the Department of Aerospace Engineering. He has held visiting positions at the Georgia Institute of Technology, DLR Institute für Stromungsforschung Göttingen, Technical University of Munich, and Potsdam Institute of Climate Impact Research.

## Research

Sujith’s research, marked by elegant experiments and theoretical insights, has significantly impacted the field of thermoacoustic instability. He redefined traditional models by demonstrating that low-amplitude aperiodic pressure fluctuations, or combustion noise, are deterministic and chaotic. He discovered the state of intermittency as the intermediate dynamical state as turbulent thermoacoustic systems transition from the state of combustion noise to the state of thermoacoustic instability. He revealed that combustion noise exhibits multifractality, which vanishes with the onset of instability. His analogy of the onset of oscillatory instabilities to Bose-Einstein condensation has provided universal scaling laws for various systems.
Sujith's introduction of complex networks to thermoacoustics has shown structural changes in network topology during transitions from combustion noise to instability, aiding in early detection of such transitions. His work has been successfully applied in industrial settings, such as GE Power & Water and ISRO's liquid rocket engines. Additionally, his research has focussed on a rich variety of topics relevant in thermoacoustic systems such as the chimera states, R-tipping, synchronization theory, amplitude death, partial amplitude death, and phase flip bifurcation. Sujith’s interdisciplinary approach, merging engineering, mathematics, and physics, has reframed thermoacoustic instabilities as self-organizing systems. This reformulation of thermoacoustic instability as “order emerging from chaos through self-organization” has attracted a large number of physicists, complex system theorists, and fluid mechanics researchers to this problem.

## Honors and awards

* 2023 - Fellow of the United States National Academy of Engineering
* 2022 - Fellow of the Combustion Institute
* 2021 - Distinguished Fellowship of the International Institute of Acoustics and Vibration
* 2019 - J. C. Bose Fellowship from the Department of Science & Technology, Government of India
* 2018 - Institute Chair Professor at IIT Madras. (Chair named as D. Srinivasan Chair in 2020)
* 2017 - August Wilhelm Scheer Visiting Professorship at TU Munich
* 2017 - Fellow of the Indian Academy of Sciences
* 2010 - Hans Fischer Senior Fellowship from Institute for Advanced Study, Technical University of Munich, Germany
* 2010 - Associate Fellow of the American Institute of Aeronautics and Astronautics
* 2008 - Fellow of the Indian National Academy of Engineering
* 2005 - Swarnajayanti Fellowship from the Department of Science & Technology, Government of India
* 2002 - Young Engineer Award, Indian National Academy of Engineering
* 2000 - Alexander von Humboldt Fellowship

## Publications

* Tipping in complex systems under fast variations of parameters (2023)
* Rijke tube: A nonlinear oscillator (2022)
* Dynamical systems and complex systems theory to study unsteady combustion (2021)
* Thermoacoustic Instability: A Complex Systems Perspective (2021)
* Complex system approach to investigate and mitigate thermoacoustic instability in turbulent combustors (2020)
* Experimental Evidence of Amplitude Death and Phase-Flip Bifurcation between In-Phase and Anti-Phase Synchronization (2018)
* Sensitivity and Nonlinearity of Thermoacoustic Oscillations (2018)
* Non-normality and nonlinearity in thermoacoustic instabilities (2016)
* Combustion noise is scale-free: transition from scale-free to order at the onset of thermoacoustic instability (2015)
* Intermittency route to thermoacoustic instability in turbulent combustors (2014)
* Non-normality and nonlinearity in combustion–acoustic interaction in diffusion flames (2008)