Research

Samadhan pioneered the application of the framework of synchronization theory to investigate the coupled interaction between the acoustic field and the heat release rate field in thermoacoustic systems. Mutual interaction between these subsystems leads to the occurrence of undesired ruinously large-amplitude tonal oscillations in propulsion and power generating systems, known as thermoacoustic instability.

Traditionally, the transition to thermoacoustic instability in turbulent combustor was considered to be a Hopf bifurcation, where the system dynamics shifts abruptly from a fixed point to limit cycle oscillations. Recently, in non-preheated turbulent combustors, such onset of thermoacoustic instability is confirmed to happen via intermittency: a state wherein bursts of periodic oscillations amidst epochs of aperiodic oscillations. Through experiments, Samadhan generalized the existence of intermittency en route to thermoacoustic instability in different combustors such as a preheated turbulent model gas-turbine combustor, a liquid rocket combustor, and a laboratory spray combustor.

Using the framework of synchronization theory, Samadhan successfully explained the intermittency route to thermoacoustic instability in turbulent combustors. He showed that the onset of thermoacoustic instability is associated with the synchronization transition of coupled subsystems - the acoustic field and the turbulent reacting field - from the state of desynchronized chaos to generalized synchronization via intermittent phase synchronization (IPS) and phase synchronization. During IPS, both the oscillators are synchronized during epochs of periodic oscillations and desynchronized during epochs of aperiodicity. This new approach based on the synchronization theory is bringing deep insights into both the temporal and spatiotemporal dynamics of turbulent combustors during the intermittency route to thermoacoustic instability. Recently, he introduced the approach of slow-fast dynamics to explain the physical reason behind the occurrence of bursting dynamics during intermittency and unravel the characteristics of different self-excited nonlinear oscillations in turbulent combustors. He has also extended the approach of forced synchronization to study flow instabilities in turbulent reacting wakes.

Samadhan developed novel mitigation strategies for thermoacoustic instabilities using different concepts from the synchronization framework. He proposed control strategies based on the amplitude death phenomenon to simultaneously quench thermoacoustic oscillations in multiple combustors. Furthermore, he explained the physics behind the mitigation of thermoacoustic instabilities through open-loop forcing in terms of the asynchronous quenching phenomenon. He invented a smart passive control strategy to mitigate thermoacoustic instability, by identifying critical regions in the spatial field of a combustor.

Performing elegant experiments using candles, he discovered many novel dynamical states, such as amplitude death, clustering, weak chimeras, and chimeras, of synchrony and oscillation quenching in minimal networks of coupled candle-flame oscillators.

In a short span of time, Samadhan made highly original and groundbreaking contributions towards obtaining a fundamental understanding of oscillatory instabilities in thermo-fluid systems and their mitigation. He aims to continue his research on using a trans-disciplinary approach based on dynamical systems and complex systems theory to understand and solve practical engineering problems. Since engineering systems are, in general, nonlinear and complex in nature, a complex systems approach provides a way to unravel the complexities that arise due to interactions between multiple parts of such systems.