Session: Rising Stars of Mechanical Engineering Celebration & Showcase

Paper Number: 149865

149865 - Understanding the Role of Buoyant Flow for Accurate and Robust Scale Modeling of Upward Flame Spread 

This project studies how fire behaviors change with scale. Laboratory-scale tests are often used in fundamental research and in technical standards to characterize the burning behaviors of materials. However, key fire behaviors change when moving from small laboratory scale to larger real-world scales found in structures and forest fires. This scalability problem is a long-standing challenge in fire science, one that limits generalizability of laboratory testing. Filling this knowledge gap will improve the relevance of standard safety tests and lead to safer structures and products. Ultimately this will save lives, money, and property for society. This project employs experiments, numerical simulations, and theoretical modeling to control, study, and predict fire behavior at various scales. The focus is on a phenomenon called buoyant flow, which varies significantly with scale. The developed scaling models will be validated against real-world testing databases maintained by industry collaborators and data from literature. This project also aims to cultivate the next generation of academic and industry leaders. This is achieved via interactive public demonstrations of fire dynamics and via promotion of technical standards in college curricula.

One of the key factors influencing fire scalability is buoyant flow. This project focuses on the effects of buoyant flow on upward flame spread over solids. In this fire scenario, the fuel sample is oriented vertically, along the direction where buoyant flow varies significantly. The coupling between solid fuel and gaseous flame is sensitive to such buoyant flow variations, making scalability even more challenging. By nature, buoyant flow is caused by a density gradient in a gravity field. By systematically varying these phenomena, buoyant flow can be manipulated. First, the effect of density are studied by varying pressure and diluents of ambient gas in a combustion chamber. Second, the effects of gravity are studied using centrifuge facilities. These experiments are augmented by calibrated numerical modeling. The small-scale data, where buoyant flow is artificially enhanced, will be compared to large-scale data from collaborators, where buoyant flow is naturally up-scaled with fire size. Dimensional analysis is also performed to identify the invariant dimensionless variable groups. Last, a new scaling model will be proposed to bridge small and large fires by incorporating buoyant flow. The project outcomes will allow creation of fire models that make fewer assumptions than ever before. The research findings will also dramatically increase the applicability of lessons from lab-scale experiments as well as allowing re-interpretation of past reduced-scale experiments.
 

Presenting Author: Ya-Ting Liao Case Western Reserve University

Presenting Author Biography: Dr. Ya-Ting T. Liao is an associate professor and the faculty director of the UL Fire and Combustion Laboratories at Case Western Reserve University. She also leads the Computational Fire Dynamics Laboratory in the Department of Mechanical and Aerospace Engineering and uses numerical modeling and experimentation to study basic fire science and fire dynamics in specific situations (e.g., forests) or in situations with unique chemistry (e.g., lithium-ion batteries). In addition to ground tests in her lab at CWRU, Dr. Liao conducts experiments on various microgravity platforms, including the US National Laboratory aboard the International Space Station and the Zero Gravity Research Facility at NASA Glenn Research Center. By combining the capabilities of micro- and normo- gravity experiments with numerical modeling, Dr. Liao explores various fire phenomena and proposes new theories and correlations in fire dynamics. Dr. Liao’s work has been supported by various funding agencies including NSF, NASA, CASIS, and UL.

Dr. Liao is performing a 8-month visiting faculty fellow research at NASA Glenn Research Center starting in Summer 2024. She also currently serves on the Board of the United State Section of the Combustion Institute, the Board of Advisors of the Central States Section of the Combustion Institute, and the Editorial Advisory Board of the Journal of Fire Science. She also serves as the faculty advisor of the Society of Women Engineers (SWE) CWRU chapter. Dr. Liao is the recipient of the 2022 Case School of Engineering Research Award, 2020 Jack Watts Award for Outstanding Reviewer of the Fire Technology Journal, the 2019 NSF CAREER Award, and the 2019 CWRU Glennan Fellowships Award.

Prior to joining the faculty at CWRU, Dr. Liao worked for two-years in the petroleum industry. From 2013-2014, she worked on thermal fluids and two-phase flow problems as a consultant and later as a thermo-fluids specialist at FMC Technologies. In 2011-2012, Dr. Liao worked at Bloomberg LP as a software developer. Dr. Liao obtained her PhD in Mechanical and Aerospace Engineering from Case Western Reserve University in 2011. She double majored in Mechanical Engineering and Physics at National Taiwan University in 2004.

Authors:

Ya-Ting Liao Case Western Reserve University