Zoom link: https://kaust.zoom.us/j/9963623876?omn=92254504287

Committee Member information:

• Ph.D. Advisor: Prof. Aamir Farooq
• External Examiner: Prof. Eric L. Petersen (Texas A&M University College of Engineering)
• Committee Chair: Prof. Hussein Hoteit
• 4^th Committee Member: Prof. Hong G. Im

Abstract

Shock tubes are a cornerstone of combustion research, enabling controlled high-temperature, high-pressure environments for precise chemical kinetic measurements. Their accuracy, however, is often reduced by non-ideal flow features such as shock velocity variation, axial thermodynamic gradients, and far-wall ignition. These effects stem from non-instantaneous diaphragm opening, boundary layer growth, and reflected shock–boundary layer interactions, and they directly compromise ignition delay time (IDT) measurements.

This dissertation examines these phenomena in single-diaphragm, double-diaphragm, and diaphragmless shock tube configurations. Experiments employ high-speed imaging and shock trajectory measurements. High-fidelity CFD simulations resolve shock formation, attenuation, and axial gradient development in both inert and reactive mixtures. Together, these methods establish a clear link between flow evolution and the reliability of chemical kinetic data.

Several advances are achieved. Realistic diaphragm and valve opening (in case of diaphragmless) profiles are implemented in CFD, enabling direct quantification of their influence on shock strength and test gas uniformity. A high-pressure diaphragmless shock tube is developed and validated for IDT measurements, achieving reduced axial gradients at the expense of some loss in shock strength. Simulations of the reflected shock region capture the coupled effects of axial gradients, bifurcation, and velocity variation across different gases. A predictive correction framework — Shock tube Prediction of Auto-ignition and Remote Kinetics (SPARK) model — is introduced to adjust IDT measurements for these gradients. Simulations of methane/air and hydrogen/air mixtures identify far-wall ignition events triggered by gradient-driven and bifurcation-induced hot spots.

These contributions culminate in a framework that links measurable flow non-uniformities to their impact on IDT accuracy. The SPARK model, developed in this work, provides a practical means to distinguish reliable IDT data from measurements compromised by axial gradients or non-ideal ignition. By enabling this differentiation, the methodology improves confidence in shock tube kinetics data and supports more rigorous interpretation of results across different facilities and operating modes.

Biography

Touqeer Anwar Kashif is a Ph.D. candidate in the Mechanical Engineering program within the PSE Division at KAUST. He began his Ph.D. at KAUST in 2021 and conducts research in Prof. Aamir Farooq’s Advanced Sensing Technology and Energy Research (FASTER) group. Kashif holds a B.Tech. degree from India and an M.S. degree from KAUST. His research focuses on developing a diaphragmless shock tube facility and understanding non-idealities in shock tubes and their impact on chemical kinetic measurements.