Askar Kazbekov
(Advisor: Prof. Adam M. Steinberg) will defend a doctoral thesis entitled,
Inter-Scale Energy Transfer in Turbulent Premixed Combustion
On
Friday, October 28 at 4 p.m.
Food Processing Technology Building, Auditorium 102 https://teams.microsoft.com/l/meetup-
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Abstract
Turbulent premixed combustion is widely used for energy conversion in power generation and 
propulsion devices. However, our understanding of the underlying fluid dynamics, combustion, and 
their interaction is still incomplete. The complexity of turbulent combustion arises from the 
non-linear, multi- scale, and multi-physics nature of the problem, which involves interactions 
between fluid dynamic and chemical processes across a myriad of length and time scales. The 
existing literature demonstrates that the dynamics of reacting turbulence does not necessarily 
follow the same phenomenology as in non- reacting incompressible turbulence. One of the key 
differences in reacting and compressible flows is the reversal of the classical turbulent energy 
cascade in a process termed as ‘backscatter’. Moreover, backscatter was shown to potentially depend 
on the magnitude of the pressure gradients across the flame; this is reflected in the 
sub-filter-scale pressure-work. Previous studies have predominantly focused on flames in 
homogeneous isotropic turbulence (HIT), in which the pressure gradients are associated with the 
flame and turbulence themselves. In contrast, practical combustors have mean pressure fields 
generated by the flow, which can induce significantly different turbulence dynamics as compared to 
non-reacting turbulence. The presented research explores the conditions at which energy backscatter 
occurs in an aerospace relevant configuration and attempts to identify the underlying physical 
mechanisms that have a leading order impact on these processes. This is done through systematic 
variation of the global equivalence ratio, the jet flow velocity, and the magnitude of the mean 
pressure field. The impact of these controlling parameters on turbulence production and energy 
backscatter is assessed through the analysis of filtered kinetic energy transport equations. 
Tomographic particle image velocimetry (TPIV) and planar laser induced fluorescence (PLIF) are used 
to measure the 3D velocity fields and planar distribution of formaldehyde, respectively; the 
relevant thermodynamic properties (e.g., density and progress variable) are estimated from PLIF 
data. Ultimately, this work provides both an assessment of the validity of current turbulence 
modeling paradigms employed in aerospace relevant combustion, as well as the data necessary to 
develop and validate new models if required.
Committee
•  Prof. Adam M. Steinberg – School of Aerospace Engineering (advisor)

•  Prof. Tim C. Lieuwen – School of Aerospace Engineering
•  Prof. Joseph Oefelein – School of Aerospace Engineering
•  Prof. Jerry M. Seitzman – School of Aerospace Engineering
•  Prof. Ellen Yi Chen Mazumdar – School of Mechanical Engineering