Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Firebrand Pile Thermal Characterization and Ignition Study of Firebrand Exposed Western Red Cedar(2021) Alascio, Joseph Anthony; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Over the past several decades, the severity of wildfires across the world has grown, resulting in increased number of structures in the Wildland–Urban Interface being destroyed, and lives lost. An ignition pathway that has been identified to contribute to most structures destroyed during a wildland fire is that of firebrand ignition. Firebrands are small burning pieces of vegetative material that are lofted ahead of the fire front. This study seeks to quantify thermal conditions experienced by building materials exposed to accumulated firebrands and to identify conditions that lead to ignition of these materials. A bench scale wind tunnel was used to house a decking material, western red cedar, on which the firebrands were deposited, which allowed for testing at different air flow velocities, while simultaneously analyzing the temperature of the solid substrate and gaseous exhaust flow constituents to identify trends in flaming and smoldering combustion. Higher peak temperatures and larger heating rates were found with the exposure of a higher air flow velocity. An increased air flow velocity also allowed for quicker, more frequent, and longer sustained flaming of the firebrand pile. A Modified Combustion Efficiency (MCE) value of 0.81 ± 0.02 for the firebrand pile across all testing conditions was quantified, which is indicative of a hybrid–smoldering/flaming combustion mode.Item Occupant Merging Behavior During Egress From High Rise Buildings(2012) Campbell, Christopher Kelly; Milke, James A; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Occupant merging behavior on stairwell landings is analyzed through the study of evacuation videos. Both flow rate and transit time analyses are conducted. Data is compared to the hydraulic model, which is presented in Chapter 3 of the SFPE Handbook. It is found that the flow ratio, which is the actual outflow rate from a merging event divided by the expected outflow per the hydraulic model, is on average 75%. The transit ratio, which is the normal transit time of the stairwell landing divided by the merging transit time, is found to be 0.67 and 0.70 for the floor and stair flows, respectively. Empirical data is compared to data collected from the Pathfinder 2011 egress model. Causes and influencing factors of occupant merging are proposed.Item THE EFFECT OF STAIR WIDTH ON OCCUPANT SPEED AND FLOW OF HIGH RISE BUILDINGS(2010) Blair, Alyson Janna; Milke, James A.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research investigates the influence of stairwell width on velocity and specific flow of occupants descending stairs during building evacuations. It examines data collected by the National Institute of Standards and Technology taken from eight different stairwells during unannounced fire drills in four buildings. Based on the raw data given by NIST the velocity, density, and specific flow were calculated for each occupant on every floor in which data was collected. Though data was noisy, results demonstrate that there is a linear trend between density of occupants in a stairwell and the velocity they descend at. There is also a parabolic trend between density and specific flow rate of occupants on stairs. While no direct correlation was found, stairwell width does seem to influence the speed and specific flow of occupants since the stairwell with the smallest effective width found occupants traveling slower. As well, the correlations in the SFPE Handbook, developed by Nelson and Mowrer concerning velocity and specific flow rate, were found to be an upper limit on the data that was analyzed.Item Spray Characteristics From Fire Hose Nozzles(2010) Salyers, Brian Edward; Marshall, Andrew W; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research examines the spray characteristics of fire hose streams. Smooth bore fire hose nozzles create jets with shear column breakup due to high Weber numbers. Laboratory settings produced a cylindrical water jet with the same column breakup behavior. The jet was injected into still air with fully developed turbulent flow. The test nozzle was oriented parallel to the floor. A patternator defined the shape and distribution of the spray. Shadowgraphy measurements determined the flow, drop size and velocity. The spray was tested in the middle of the liquid core.