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Stalcup, Erik JamesNumerical Modeling of Upward Flame Spread and Burning of Wavy Thin Solids
Master of Sciences, Case Western Reserve University, EMC - Aerospace Engineering
Flame spread over solid fuels with simple geometries has been extensively studied in the past, but few have investigated the effects of complex fuel geometry. This study uses numerical modeling to analyze the flame spread and burning of wavy (corrugated) thin solids and the effect of varying the wave amplitude. Sensitivity to gas phase chemical kinetics is also analyzed. Fire Dynamics Simulator is utilized for modeling. The simulations are two-dimensional Direct Numerical Simulations including finite-rate combustion, first-order pyrolysis, and gray gas radiation. Changing the fuel structure configuration has a significant effect on all stages of flame spread. Corrugated samples exhibit flame shrinkage and break-up into flamelets, behavior not seen for flat samples. Increasing the corrugation amplitude increases the flame growth rate, decreases the burnout rate, and can suppress flamelet propagation after shrinkage. Faster kinetics result in slightly faster growth and more surviving flamelets. These results qualitatively agreement with experiments.

Committee:

James T'ien (Committee Chair); Joseph Prahl (Committee Member); Yasuhiro Kamotani (Committee Member)

Subjects:

Aerospace Engineering; Fluid Dynamics; Mechanical Engineering

Keywords:

modeling;simulation;numerical modeling;combustion;computational combustion;direct numerical simulation;flame spread;burning;wavy;corrugated;fire dynamics simulator;FDS;fuel structure;fuel geometry;complex geometry;cardboard;

Bova, Anthony ScottModeling the Ventilation of Natural Animal Shelters in Wildland Fires
Master of Science, The Ohio State University, 2010, Civil Engineering

The level of protection from wildland fires that tree cavities provide to sheltered fauna is not well understood. Further, few experiments have been performed to investigate the transfer of combustion products into, and ventilation of, tree cavity shelters in wildland fires. This paucity of data is unlikely to change in the near future. However, increasingly realistic fluid and fire dynamics simulation software has made the execution of “virtual experiments” tenable. In such experiments, data from simulations are used to form empirical relationships between the investigated phenomena and simulated conditions. As an example of this approach, the National Institute of Standards and Technology’s (NIST) Fire Dynamics Simulator (FDS) was used to create formulas for estimating maximum combustion product concentrations, doses (concentration integrated over time) and maximum gas temperatures within a single-entrance cylindrical shelter at heights above 3 m.

A three-step approach was taken: First, FDS was validated for single-entrance ventilation by comparison of simulation results to data from large- and small-scale ventilation experiments. Second, data from 45 simulations of a single-entrance, cylindrical shelter subjected to frontal winds at various speeds, angles of incidence and temperatures, were used to create empirical formulas relating these variables to entrance flux and rates of temperature change. Third, these formulas were applied to data from 26 separate simulations of different surface fire scenarios. As a result, a single empirical formula was found relating gas concentrations, doses and maximum temperatures inside a shelter to fire intensity, flame depth and wind speed. The findings suggest that virtual experiments can help provide tools for forest and land managers to estimate the impact and minimize the hazards of prescribed burning, as well as evaluate the consequences of naturally occurring wildland fires.

Committee:

Gil Bohrer, PhD (Advisor); Matthew Dickinson, PhD (Committee Member); Ethan Kubatko, PhD (Committee Member); John Lenhart, PhD (Committee Member)

Subjects:

Environmental Engineering; Environmental Science; Fluid Dynamics

Keywords:

wildland fire; animal shelter; cavity ventilation; fire dynamics simulator

Rajput, PrafullaA Model of the Emission and Dispersion of Pollutants From a Prescribed Forest Fire in a Typical Eastern Oak Forest
Master of Science (MS), Ohio University, 2010, Chemical Engineering (Engineering and Technology)
A simulation model is completed to study the emission and dispersion of carbon dioxide, carbon monoxide, particulate matter and the temperature variation caused from prescribed forest burning in a typical eastern hardwood forest. The purpose of the present study is to estimate of the output quantities from the fire and exposure to them for life in the vicinity of the fire. A FORTRAN code is generated which is furnished as an input to the Fire Dynamic Simulator (FDS) model to simulate the realistic scenario of a prescribed fire which occurred at the Arch Rock forest in south eastern Ohio. This FORTRAN model, which provided terrain elevation, heat release, wind flow, soot yield data for the Arch Rock burning scenario, was built using MATLAB. The heat data was collected by hovering planes over the fire carrying remote sensing equipment which recorded the Infra Red radiation from the fire. The results show spatially and temporally resolved emissions from the fire and how long surrounding life is exposed. The resultant concentration values give an idea of the extent of the harmful pollutants released from the fire.

Committee:

Valerie L. Young, PhD (Advisor)

Subjects:

Chemical Engineering; Engineering; Environmental Science; Fluid Dynamics

Keywords:

Fire Dynamics simulator; prescribed fire modeling; FDS; forest fire modeling;