Cornell University

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MAE Seminar: Sadaf Sobhani, Ph.D. candidate (Stanford University), "The Tortuous Path to Application-Tailored Porous Structures"

Thursday, March 7, 2019 at 4:30pm

Upson Hall, 206

ABSTRACT:  The pore-scale microstructure of a porous medium determines its macroscale properties such as strength, flexibility, fluid permeability, and heat transfer. Natural systems have evolved to harness this relationship to achieve desired functions. For example, our bones have different porosities depending on local weight-bearing requirements, and the wood in tree trunks has different pore arrangements to optimize water transport according to the surrounding climate. Conversely, in many emerging technologies, the potential for tailoring the porous medium remains largely untapped due to the computational and experimental limitations associated with multi-scale multi-physics transport in a complex and optically inaccessible geometry.

I present an integrated framework for applying insights gained from the fundamental analysis of flow and thermal transport in porous media to tailor designs relevant for reliable heat-shielding materials for safe spacecraft reentry and clean high-efficiency combustion systems. First, high-fidelity simulations of radiative heat transfer in fibrous materials are combined with x-ray tomography digital renderings of real thermal protection materials to develop reduced-order models of radiation transport. Second, a theoretical analysis of coupled heat transfer in porous foams leads to a new morphology gradation concept for combustion in porous media. Results from reduced-order models illustrate significant enhancements of the power-dynamic range and flame blow-off limits compared to those of conventional burners. This proof-of-concept is validated experimentally using 3D printed burners obtained by lithography-based ceramic manufacturing. Both systems highlight the bottlenecks and potential advantages associated with tailoring porous structures towards creating smart solutions to engineering challenges, including applications to carbon dioxide sequestration, fuel cells, and catalytic systems.

BIOGRAPHICAL SKETCH:  Sadaf Sobhani is a Mechanical Engineering Ph.D. candidate at Stanford University and researcher at the NASA Ames Research Center. In addition to advancing high-fidelity numerical and non-intrusive experimental capabilities for complex flows in porous media, she contributes reduced-order models that enable probing novel design concepts as well as additive manufacturing strategies for their fabrication. 

She is the recipient of an NSF Graduate Research Fellowship, Accel Innovation Scholarship for entrepreneurship, Enhancing Diversity in Graduate Education Fellowship, American Physical Society’s Gallery of Fluid Motion Award, and Graduate Public Service Fellowship. She has authored a whitepaper on clean fuels policy at the United Nations Foundation, supported by the Schneider Sustainable Energy Fellowship. She earned her Bachelor’s and Master’s degrees in Mechanical Engineering from Stanford University.

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