Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

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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    THE INFLUENCE OF WIND ON THE STRUCTURE OF INCLINED FLAMES
    (2020) Heck, Michael; Gollner, Michael J; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Experiments were performed using stationary gas burners in order to characterize the flame geometry and downstream heating from stationary flames under inclined configurations under an applied forced flow. Stationary flames exhibit behavior similar to spreading wildland fires but are an ideal configuration for carefully studying fundamental wildland fire behavior characteristics that play a critical role in downstream heating, which subsequently drive fire spread. Two conditions were applied to a small-scale apparatus during experimentation, a sloped surface and forced-flow wind. The experiments were performed at multiple heat-release rates for angles from 0 to 28 degrees from the horizontal and wind speeds of 0 to 0.5 m/s.Flame geometry such as center-line flame length, flame tilt angle, and flame attachment length along the downstream surface were determined from side-view video imaging. Downstream heating was also measured through fine-wire thermocouple temperature measurements and surface total heat heat flux measurements. The measurements provided a heating profile depicting the magnitude of heating that would be applied to unburned fuels at distances in front of a spreading fire. These profiles were compared to the flame attachment observed from imaging, and to one another. While the surface heat flux cannot be scaled to larger fires, it’s relation to temperature profiles will be useful to further interpret large-scale experiments and as validation data for numerical modeling of fire behavior of the combined effects of slope and wind
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    UNDERSTANDING THE INFLUENCE OF WIND AND SLOPE ON FLAMES IN WILDLAND FIRES
    (2019) Sluder, Evan; Gollner, Michael J; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Wildland fire spread is typically described as a function of fuel, weather, and topography. An understanding of how these parameters are interrelated can help to close the gap on our understanding of the flame spread process. Fire spread over steep slopes is unique because the flame dramatically transitions from a detached, “plume” mode to an attached “boundary layer” mode at what appears to be a critical angle. The change in flame shape significantly increases the rate of spread by increasing the length and magnitude of heating ahead of the burning region. This attachment behavior has been observed in the literature, however the correlation between fire intensity, slope, wind, and flame shape is not yet well described or in a form which allows for prediction of fire behavior. A series of experiments using stationary gas burners have been undertaken to describe the behavior of a steady flame at multiple slopes under both wind and non-wind conditions. A stationary gas burner has been used to emulate flames under various fire intensities, burner aspect ratios, slopes, and wind conditions. A small-scale apparatus was first used to image hot gases using a shadowgraph technique coupled with downstream temperature measurements. Later a larger-scale apparatus was used with downstream temperature measurements to determine instantaneous downstream heating lengths. Both steady and time-dependent analysis of the attachment process is presented, along with its relation to fire spread. Based on the observed trends from these relationships non-dimensional parameters are introduced to relate the effects of inclination, wind, fire size and aspect ratio to the length of the heating region ahead of the burner. It is proposed that this value may be useful as a simple way to incorporate these effects in a wildland fire spread model.