Dissertation Defense – Dushyant Chaudhari

Title: Experiments and Semi-empirical Modeling of Buoyancy-driven, Turbulent Frame Spread over Combustible Solids in a Corner Configuration.

Author: Dushyant Chaudhari

Day/Time: Aug 4, 2021 09:00 AM Eastern Time (US and Canada)

Examining Committee:
Professor Stanislav I. Stoliarov, Chair
Professor Christopher Cadou, Dean’s Representative
Professor Arnaud Trouvé
Professor Johan Larsson 
Dr. Isaac Leventon

Abstract: The increased use of engineered complex polymeric materials in the construction industry has highlighted their fire hazard. Standardized testing of materials, especially those in the developmental stage, is necessary for screening them for safe commercial application. However, testing can be expensive, hindering the process of development. This research aims to investigate the possibility of utilization of computational capability to predict fire hazard for facilitating screening of wall-lining materials in an important standardized configuration – a corner geometry without a ceiling. It also aims to fundamentally understand the dynamics of interactions between condensed-phase pyrolysis, gas-phase combustion, and flame heat feedback during concurrent, buoyancy-driven flame spread. Consequently, a series of hierarchical experiments and modeling from small-scale (to develop comprehensive pyrolysis models) to large-scale scenarios (to study flame spread fire dynamics) using samples having mass between a milligram to a kilogram were performed. Small-scale experimental data were inversely analyzed using a hill-climbing optimization technique in a comprehensive pyrolysis solver, ThermaKin. Large-scale experiments performed over a non-charring, non-swelling material with well-characterized condensed-phase pyrolysis – Poly (methyl methacrylate) (PMMA) – provided valuable data for fast-response (13 s response) calorimetry, well-resolved flame heat feedback at 28 locations, and radiation intensities at spectrally-resolved narrowband wavelength corresponding to soot emissions during the flame spread. An empirical flame heat feedback model obtained from large-scale experiments conducted over PMMA was then coupled with the pyrolysis model to develop a low-cost, fast, semi-empirical model for simulating fire dynamics during flame spread. The hierarchical experiments and modeling framework was further applied to two important wall-lining materials – Polyisocyanurate (PIR) foam and Oriented Strand Board (OSB) to scrutinize the robustness of the developed modeling framework. The study has presented a systematic methodology that reasonably predicted the fire dynamics in the large-scale tests over the three studied materials and can be judiciously extended to other materials. It has also emphasized the importance of significantly reducing pyrolysis parameter uncertainties, of understanding convection-radiation contribution to the flame heat feedback, and of investigating the use of an empirical flame heat feedback model as being fuel-independent to further improve the large-scale modeling predictions.