Illuminating Complex Flows: Optical Diagnostics for Aerospace Applications

Hypersonic flight represents a major frontier in aerospace engineering, with its realization requiring a fundamental understanding of coupled chemical and fluid dynamic processes across multiple environments. Of particular importance are the reacting flows within the propulsion systems that enable sustained hypersonic flight and the high-temperature, chemically reacting flows that develop near vehicle surfaces at extreme speeds. Understanding the complex and strongly coupled phenomena governing these environments requires a synergistic combination of high-fidelity computation and carefully designed experiments. Experimental investigations, however, are inherently challenging, often relying on sophisticated ground-based facilities equipped with advanced diagnostic capabilities to generate meaningful, high-resolution data. Among these, optical diagnostics have emerged as a powerful class of measurement tools, offering significant advantages over conventional techniques. Their non-intrusive nature, high temporal resolution, and robustness under extreme conditions make them uniquely suited for probing high-speed, high-enthalpy flows. Continued advances in optical diagnostics have enabled transformative progress across multiple domains of aerospace research, including chemical kinetics, aerodynamics, and active flow control.

This talk will focus on a specific application of advanced optical diagnostics: elucidating the chemical kinetics of complex fuels such as jet fuels, gasoline surrogates, and rocket propellants under engine-relevant conditions. Particular emphasis will be placed on the role of advanced laser-based diagnostics, coupled with shock tube reactors, in uncovering fundamental insights into the behavior of large hydrocarbons and their mixtures at elevated temperatures and pressures. These insights have enabled the development of the Low-Temperature Hybrid Chemistry (LT-HyChem) framework, a methodology for constructing compact, fuel-specific chemical kinetic models that remain valid across the full range of operating conditions relevant to modern and next-generation propulsion systems. The LT-HyChem approach is fuel-agnostic and produces models that are over two orders of magnitude more compact than those generated using conventional methodologies, while simultaneously reducing predictive uncertainties by more than an order of magnitude. This combination of compactness and accuracy facilitates integration with computational fluid dynamics solvers, significantly reducing the computational cost associated with combustor design, analysis, and optimization. The talk will conclude with a discussion of the broader implications of this work for rapid screening of sustainable aviation fuels and potential extensions to solid fuel systems.

Speaker: Dr. Rishav Choudhary

Biography:
Dr. Rishav Choudhary received his B.Tech. in Aerospace Engineering from IIT Kanpur and his M.S. and Ph.D. in Mechanical Engineering from Stanford University. His doctoral research focused on absorption-spectroscopy-based diagnostics for chemical kinetics under extreme conditions relevant to engine combustion, hypersonic re-entry, and other high-temperature environments. He subsequently worked as a Postdoctoral Researcher in Aerospace Engineering at the University of Michigan, developing optical diagnostics for high-speed density fluctuations, velocity measurements in supersonic flows, and electron-density measurements in plasmas. He is currently an Engineer at Lam Research Corporation, where his work involves optical diagnostics applied to multiphase flows and plasmas relevant to semiconductor manufacturing.

Note: Dr. Rishav Choudhary is a faculty candidate in the Propulsion stream in the Department of Aerospace Engineering, IISc. Faculty members are encouraged to attend the talk and interact with the candidate.