Publications
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Liao, Ya-Ting; Carmignani, Luca; Niehaus, Justin; Gollner, Michael; Belmont, Erica; Bhattacharjee, Subrata; Ris, John; Dietrich, Daniel; Eigenbrod, Christian; Endo, Makoto; others,
Topical: Challenges and Research Needs for Micro-and Partial-Gravity Fires Journal Article
In: 2021.
@article{liao2021topical,
title = {Topical: Challenges and Research Needs for Micro-and Partial-Gravity Fires},
author = {Ya-Ting Liao and Luca Carmignani and Justin Niehaus and Michael Gollner and Erica Belmont and Subrata Bhattacharjee and John Ris and Daniel Dietrich and Christian Eigenbrod and Makoto Endo and others},
year = {2021},
date = {2021-01-01},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Gollner, Michael; Wichman, Indrek; Liao, Ya-Ting; Carmignani, Luca; Belmont, Erica; Bhattacharjee, Subrata; Ris, John; Dietrich, Daniel; Eigenbrod, Christian; Endo, Makoto; others,
Topical: Solid Fuel Combustion in Partial and Micro-Gravity Journal Article
In: 2021.
@article{gollner2021topical,
title = {Topical: Solid Fuel Combustion in Partial and Micro-Gravity},
author = {Michael Gollner and Indrek Wichman and Ya-Ting Liao and Luca Carmignani and Erica Belmont and Subrata Bhattacharjee and John Ris and Daniel Dietrich and Christian Eigenbrod and Makoto Endo and others},
year = {2021},
date = {2021-01-01},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Gollner, Michael J; Garg, Priya; Roche, Thomas; Eden, Matthew; Matz, Jacqueline; Oakes, Jessica M; Bellini, Chiara
Effect of moisture content and fuel type on emissions from vegetation using a steady state combustion apparatus Journal Article
In: 2021.
@article{gollner2021effect,
title = {Effect of moisture content and fuel type on emissions from vegetation using a steady state combustion apparatus},
author = {Michael J Gollner and Priya Garg and Thomas Roche and Matthew Eden and Jacqueline Matz and Jessica M Oakes and Chiara Bellini},
year = {2021},
date = {2021-01-01},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Yu Hu Sriram Bharath Hariharan, Michael J. Gollner; Oran, Elaine S.
Effects of circulation and buoyancy on the transition from a fire whirl to a blue whirl Journal Article
In: Physical Review Fluids, vol. 5, no. 103201, 2020.
@article{hariharan2020PRL,
title = {Effects of circulation and buoyancy on the transition from a fire whirl to a blue whirl},
author = {Sriram Bharath Hariharan, Yu Hu, Michael J. Gollner, and Elaine S. Oran},
url = {http://firelab.berkeley.edu/wp-content/uploads/2021/01/2020-PhysRevFluids.5.103201-effects-of-circulation-and-buouyancy-on-the-transition-from-a-fire-whirl-to-a-blue-whirl_PREPRINT.pdf},
doi = {10.1103/PhysRevFluids.5.103201},
year = {2020},
date = {2020-10-14},
journal = {Physical Review Fluids},
volume = {5},
number = {103201},
abstract = {The relative influence of circulation and buoyancy on fire whirls (FWs), blue whirls (BWs), and the transition between these regimes of a whirling flame is investigated using a combination of experimental data and scaling analyses. FWs are whirling, turbulent, cylindrical yellow (sooting) flame structures that form naturally in fires and are here created in laboratory experiments. In contrast, a BW is a laminar, blue flame (nonsooting) with an inverted conical shape. Measurements of the circulation and heat-release rate are combined with measurements of the flame geometry, defined by the flame width and the height, to provide characteristic length scales for these whirling-flame regimes. Using these, a nondimensional circulation (Γ∗f) and a heat-release rate (˙Q∗f) were defined and shown to correspond to azimuthal and axial (buoyancy driven) momenta, respectively. The ratio R∗=Γ∗f/˙Q∗f, a quantity analogous to the swirl number used to characterize swirling jets, was evaluated for FWs and BWs. For FWs, R∗\<1, so that axial momentum is greater than azimuthal momentum and the flame is dominated by buoyant momentum. For BWs, R∗\>1, so that the flame is circulation dominated. This is argued to be consistent with vortex breakdown being an important part of the transition of FWs to BWs. This work presents a basis for predicting when a BW will form and remain a stable regime.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
W. Coenen R.S.P. Hakes, A. L. Sánchez
Stability of laminar flames on upper and lower inclined fuel surfaces Journal Article Forthcoming
In: Proceedings of the Combustion Institute, Forthcoming.
@article{hakes2020proci,
title = {Stability of laminar flames on upper and lower inclined fuel surfaces},
author = {R.S.P. Hakes, W. Coenen, A.L. S\'{a}nchez, M.J. Gollner, F.A. Williams},
url = {https://doi.org/10.1016/j.proci.2020.06.302},
doi = {10.1016/j.proci.2020.06.302},
year = {2020},
date = {2020-09-01},
journal = {Proceedings of the Combustion Institute},
abstract = {Experiments have found substantial morphological differences between buoyancy-driven flames developing on the upper and lower surfaces of inclined burning plates. These differences cannot be explained on the basis of existing analytical solutions of steady semi-infinite flames, which provide identical descriptions for the top and bottom configurations. To investigate the potential role of flame instabilities in the experimentally observed flow differences, a temporal linear stability analysis is performed here. The problem is formulated in the limit of infinitely fast reaction, taking into account the non-unity Lewis number of the fuel vapor. The stability analysis incorporates non-parallel effects of the base flow and considers separately spanwise traveling waves and G\"{o}rtler-like streamwise vortices. The solution to the stability eigenvalue problem determines the downstream location at which the flow becomes unstable, characterized by a critical value of the relevant Grashof number, whose value varies with the plate inclination angle. The results for the flame formed on the underside of the fuel surface indicate that instabilities emerge farther downstream than they do for a flame developing over the top of the fuel surface, in agreement with experimental observations. Increased buoyancy-induced vorticity production is reasoned to be responsible for the augmented instability tendency of topside flames.
},
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
Bryce Bathras Zhenxiang Tao, Byoungchul Kwon
Effect of firebrand size and geometry on heating from a smoldering pile under wind Journal Article Forthcoming
In: Fire Safety Journal, Forthcoming.
@article{Tao2020,
title = {Effect of firebrand size and geometry on heating from a smoldering pile under wind},
author = {Zhenxiang Tao, Bryce Bathras, Byoungchul Kwon, Ben Biallas, Michael Gollner, Rui Yang},
doi = {https://doi.org/10.1016/j.firesaf.2020.103031},
year = {2020},
date = {2020-05-07},
journal = {Fire Safety Journal},
abstract = {Smoldering firebrands can be lofted over long distances, easily igniting spot fires. This poses a threat to structures in the wildland-urban interface (WUI), where wildland fires spread into and within communities. This study investigates the influence of firebrand size and makeup on heating from a pile to a recipient surface in a small-scale wind tunnel. Two sizes of fluted birch wooden pins and wooden discs, one size of cylindrical birch dowels, two lengths of eucalyptus sticks, and pine bark flakes were used to simulate firebrands; all with 4 g of smoldering brands deposited. The porosity of the different firebrand piles, the heat flux to an inert test surface, spatial measurements of surface temperature, and videos of the experiments were recorded and analyzed. It was found that the realistic fuels, i.e. pine bark and eucalyptus sticks, could achieve higher peak heat fluxes than artificial birch fuels at higher wind speeds …
},
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
Dong Zeng Xingyu Ren, Yi Wang
Temperature measurement of a turbulent buoyant ethylene diffusion flame using a dual-thermocouple technique Journal Article Forthcoming
In: Fire Safety Journal, Forthcoming.
@article{Ren2020,
title = {Temperature measurement of a turbulent buoyant ethylene diffusion flame using a dual-thermocouple technique},
author = {Xingyu Ren, Dong Zeng, Yi Wang, Gang Xiong, Gaurav Agarwal, Michael Gollner
},
url = {https://doi.org/10.1016/j.firesaf.2020.103061},
doi = {10.1016/j.firesaf.2020.103061},
year = {2020},
date = {2020-05-07},
journal = {Fire Safety Journal},
abstract = {High-frequency temperature measurements were carefully conducted for a 15 kW buoyant turbulent ethylene diffusion flame over a 15.2 cm diameter gas burner with air co-flow. A dual-thermocouple probe, consisting of two fine-wire thermocouples with 25 μm and 50 μm wire diameters, was used to determine a compensated turbulent gas temperature. A sensitivity analysis shows that temperatures resolved using this dual-thermocouple technique are less sensitive to changes in thermocouple bead size, therefore, uncertainty is greatly reduced even when soot deposition on the thermocouple bead occurs in sooty flames. Mean and root-mean square (rms) fluctuations of gas temperature were recorded in a two-dimensional plane across the flame centerline. The mean gas temperature monotonically decreases away from the flame centerline at most flame heights, except for 1 diameter above the burner, where a …
},
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
Gollner, Michael J
Ignition-Resistant Communities Book Section
In: Encyclopedia of Wildfires and Wildland-Urban Interface (WUI) Fires, pp. 1–3, Springer International Publishing, Cham, 2020, ISBN: 9783319517278.
@incollection{Gollner2020,
title = {Ignition-Resistant Communities},
author = {Michael J Gollner},
url = {http://link.springer.com/10.1007/978-3-319-51727-8_227-1},
doi = {10.1007/978-3-319-51727-8_227-1},
isbn = {9783319517278},
year = {2020},
date = {2020-01-01},
booktitle = {Encyclopedia of Wildfires and Wildland-Urban Interface (WUI) Fires},
pages = {1--3},
publisher = {Springer International Publishing},
address = {Cham},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
May, Nathaniel; Gollner, Michael J
Fire Emissions Book Section
In: Manzello, Samuel (Ed.): pp. 1–7, 2020, ISBN: 9783319517278.
@incollection{May2020,
title = {Fire Emissions},
author = {Nathaniel May and Michael J Gollner},
editor = {Samuel Manzello},
doi = {10.1007/978-3-319-51727-8_123-1},
isbn = {9783319517278},
year = {2020},
date = {2020-01-01},
journal = {Encyclopedia of Wildfires and Wildland-Urban Interface (WUI) Fires},
pages = {1--7},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
Manzello, Samuel L; Suzuki, Sayaka; Gollner, Michael J; Fernandez-Pello, Carlos A
Role of firebrand combustion in large outdoor fire spread Journal Article
In: Progress in Energy and Combustion Science, vol. 76, pp. 100801, 2020, ISSN: 0360-1285.
@article{MANZELLO2020100801,
title = {Role of firebrand combustion in large outdoor fire spread},
author = {Samuel L Manzello and Sayaka Suzuki and Michael J Gollner and Carlos A Fernandez-Pello},
url = {http://www.sciencedirect.com/science/article/pii/S0360128519300942},
doi = {https://doi.org/10.1016/j.pecs.2019.100801},
issn = {0360-1285},
year = {2020},
date = {2020-01-01},
journal = {Progress in Energy and Combustion Science},
volume = {76},
pages = {100801},
abstract = {Large outdoor fires are an increasing danger to the built environment. Wildfires that spread into communities, labeled as Wildland-Urban Interface (WUI) fires, are an example of large outdoor fires. Other examples of large outdoor fires are urban fires including those that may occur after earthquakes as well as in informal settlements. When vegetation and structures burn in large outdoor fires, pieces of burning material, known as firebrands, are generated, become lofted, and may be carried by the wind. This results in showers of wind-driven firebrands that may land ahead of the fire front, igniting vegetation and structures, and spreading the fire very fast. Post-fire disaster studies indicate that firebrand showers are a significant factor in the fire spread of multiple large outdoor fires. The present paper provides a comprehensive literature summary on the role of firebrand mechanisms on large outdoor fire spread. Experiments, models, and simulations related to firebrand generation, lofting, burning, transport, deposition, and ignition of materials are reviewed. Japan, a country that has been greatly influenced by ignition induced by firebrands that have resulted in severe large outdoor fires, is also highlighted here as most of this knowledge remains not available in the English language literature. The paper closes with a summary of the key research needs on this globally important problem.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Zhao, Kun; Gollner, Michael J; Liu, Qiong; Gong, Junhui; Yang, Lizhong
Lateral flame spread over PMMA under forced air flow Journal Article
In: Fire Technology, vol. 56, no. 2, pp. 801–820, 2020.
@article{zhao2020lateral,
title = {Lateral flame spread over PMMA under forced air flow},
author = {Kun Zhao and Michael J Gollner and Qiong Liu and Junhui Gong and Lizhong Yang},
year = {2020},
date = {2020-01-01},
journal = {Fire Technology},
volume = {56},
number = {2},
pages = {801--820},
publisher = {Springer US},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Zhao, Kun; Gollner, Michael J; Liu, Qiong; Gong, Junhui; Yang, Lizhong
Lateral Flame Spread over PMMA Under Forced Air Flow Journal Article
In: Fire Technology, 2019, ISSN: 0015-2684.
@article{Zhao2019,
title = {Lateral Flame Spread over PMMA Under Forced Air Flow},
author = {Kun Zhao and Michael J Gollner and Qiong Liu and Junhui Gong and Lizhong Yang},
url = {https://doi.org/10.1007/s10694-019-00904-x http://link.springer.com/10.1007/s10694-019-00904-x},
doi = {10.1007/s10694-019-00904-x},
issn = {0015-2684},
year = {2019},
date = {2019-09-01},
journal = {Fire Technology},
publisher = {Springer US},
abstract = {In wildland and other flame spread scenarios a spreading fire front often forms an elliptical shape, incorporating both forward and lateral spread. While lateral flame spread is much slower than forward rates of spread, it still contributes to the growth of the overall fire front. In this work, a small-scale experiment is performed to investigate the mechanisms causing this lateral spread in a simple, small-scale configuration. PMMA strips with thicknesses ranging from 1 mm to 3.1 mm and widths of 5 cm and 10 cm were ignited under forced flow in a laminar wind tunnel. Unlike traditional concurrent or opposed flame spread experiments, flames were allowed to progress from one side of the sample to the other, perpendicular to the wind direction. An infrared camera was used to track the progression of the pyrolysis front by estimating the surface temperature of the PMMA. The flame spread rate, depth of the burning region, thermal diffusion length, and radiant heat flux were determined and analyzed. Based on a theory of heat and mass transfer for a laminar diffusion flame, a thermal heat transfer model was developed for the preheating region to predict the lateral flame spread rate. Results show that the thermal diffusion length decreases with wind velocity, ranging from 4.5 mm to 3 mm. Convection dominates the flame-spread rate, accounting for more than 80% of the total heat flux. The theoretical flame spread rate agrees well with experimental data from all but the thinnest samples tested, overpredicting the lateral flame spread rate for 1 mm thick samples. The resulting model for lateral flame spread under concurrent flow works for forced-flow dominated flame spread over thermally-thin fuels and helps provide physical insight into the problem, aiding in future development of two-dimensional, elliptical fire spread models.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hakes, Raquel S P; Salehizadeh, Hamed; Weston-Dawkes, Matthew J; Gollner, Michael J
Thermal characterization of firebrand piles Journal Article
In: Fire Safety Journal, vol. 104, pp. 34–42, 2019, ISSN: 03797112.
@article{Hakes2019,
title = {Thermal characterization of firebrand piles},
author = {Raquel S P Hakes and Hamed Salehizadeh and Matthew J Weston-Dawkes and Michael J Gollner},
url = {https://linkinghub.elsevier.com/retrieve/pii/S0379711218302698},
doi = {10.1016/j.firesaf.2018.10.002},
issn = {03797112},
year = {2019},
date = {2019-03-01},
journal = {Fire Safety Journal},
volume = {104},
pages = {34--42},
publisher = {Elsevier Ltd},
abstract = {The cause of the majority of structure losses in wildland-urban interface fires is ignition via firebrands, small pieces of burning material generated from burning vegetation and structures. To understand the mechanism of these losses, small-scale experiments designed to capture heating from firebrand piles and to describe the process of ignition were conducted using laboratory-fabricated cylindrical wooden firebrands. Two heat flux measurement methods were compared, and the influences of firebrand diameter, pile mass, and wind on heating from firebrand piles were explored. Diameter had little effect on heating, pile mass a moderate effect, and wind a large effect. Peak heat fluxes showed distinct differences between heat fluxes produced by firebrand piles as opposed to individual firebrands, which have been studied exclusively on the small-scale in the past. Above a critical mass, piles did not produce higher heat fluxes; however, they heated fuels for an increasingly longer duration and over a larger area. Water-cooled heat flux gauges provided reliable heat flux measurements for large firebrand piles and an array of thin-skin calorimeters indicated significant spatial variation in heat flux. A recipient fuel transitioned from smoldering to flaming under an adequate wind speed soon after a firebrand pile was deposited on its surface.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
May, Nathaniel; Ellicott, Evan; Gollner, Michael
An examination of fuel moisture, energy release and emissions during laboratory burning of live wildland fuels Journal Article
In: International Journal of Wildland Fire, vol. 28, no. 3, pp. 187–197, 2019, ISSN: 10498001.
@article{May2019,
title = {An examination of fuel moisture, energy release and emissions during laboratory burning of live wildland fuels},
author = {Nathaniel May and Evan Ellicott and Michael Gollner},
doi = {10.1071/WF18084},
issn = {10498001},
year = {2019},
date = {2019-01-01},
journal = {International Journal of Wildland Fire},
volume = {28},
number = {3},
pages = {187--197},
abstract = {A series of small-scale laboratory fires were conducted to study the relationship between fuel type, moisture content, energy released and emissions during the combustion process of live wildland fuels. The experimental design sought to understand the effects that varying moisture content of different fire-promoting plant species had on the release of total energy, gaseous emissions (CO, CO2), particulate matter less than 2.5µm in diameter (PM2.5) and fire radiative energy (FRE). Instantaneous FRE, or fire radiative power (FRP), is an important parameter used in remote sensing to relate the emitted energy to the biomass fuel consumption. Currently, remote sensing techniques rely on empirically based linear relationships between emitted FRE and biomass consumed. However, this relationship is based on the assumption that all fuels emit the same amount of energy per unit mass, regardless of fuel conditions (type, moisture, packing, orientation, etc.). In this study, we revisited these assumptions under the influence of moisture content for species that are adapted to fire, containing volatile oils. Results show that, in terms of the total energy released, this assumption holds fairly well regardless of fuel type and moisture content. However, FRE was found to be slightly dependent on the fuel type and very dependent on the moisture content of the fuel. Most of this variation was attributed to changes in the behaviour of the combustion process for different fuels, similarly observed in emissions measurements. These results highlight a need to further examine the role of fuel moisture and combustion state when determining emissions from remotely sensed measurements.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hariharan, Sriram Bharath; Sluder, Evan T; Gollner, Michael J; Oran, Elaine S
Thermal structure of the blue whirl Journal Article
In: Proceedings of the Combustion Institute, vol. 37, no. 3, pp. 4285–4293, 2019, ISSN: 15407489.
@article{Hariharan2019,
title = {Thermal structure of the blue whirl},
author = {Sriram Bharath Hariharan and Evan T Sluder and Michael J Gollner and Elaine S Oran},
url = {https://linkinghub.elsevier.com/retrieve/pii/S1540748918301160},
doi = {10.1016/j.proci.2018.05.115},
issn = {15407489},
year = {2019},
date = {2019-01-01},
journal = {Proceedings of the Combustion Institute},
volume = {37},
number = {3},
pages = {4285--4293},
abstract = {textcopyright 2018 Elsevier Ltd. The blue whirl is a recently discovered regime of the fire whirl that burns without any visible soot, even while burning liquid fuels directly. This flame evolves naturally from a traditional fire whirl in a fixed-frame self-entraining fire whirl experimental setup. Here, detailed thermal measurements of the flame structure performed using thermocouples and thin-filament pyrometry are presented. Thermocouple measurements reveal a peak temperature of ~2000 K, and 2-D temperature distributions from pyrometry measurements suggest that most of the combustion occurs in the relatively small, visibly bright, blue vortex ring. Different liquid hydrocarbon fuels such as heptane, iso-octane and cyclohexane consistently formed the blue whirl with similar thermal structures, indicating that blue whirl formation is independent of fuel type, and also that the transition from a fire whirl to a blue whirl may be influenced by vortex breakdown.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Caton-Kerr, Sara E; Tohidi, Ali; Gollner, Michael J
Firebrand Generation From Thermally-Degraded Cylindrical Wooden Dowels Journal Article
In: Frontiers in Mechanical Engineering, vol. 5, no. June, pp. 1–12, 2019, ISSN: 2297-3079.
@article{Caton-Kerr2019,
title = {Firebrand Generation From Thermally-Degraded Cylindrical Wooden Dowels},
author = {Sara E Caton-Kerr and Ali Tohidi and Michael J Gollner},
doi = {10.3389/fmech.2019.00032},
issn = {2297-3079},
year = {2019},
date = {2019-01-01},
journal = {Frontiers in Mechanical Engineering},
volume = {5},
number = {June},
pages = {1--12},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hariharan, Sriram Bharath; Anderson, Paul M; Xiao, Huahua; Gollner, Michael J; Oran, Elaine S
The blue whirl: Boundary layer effects, temperature and OH* measurements Journal Article
In: Combustion and Flame, vol. 203, pp. 352–361, 2019, ISSN: 15562921.
@article{Hariharan2019a,
title = {The blue whirl: Boundary layer effects, temperature and OH* measurements},
author = {Sriram Bharath Hariharan and Paul M Anderson and Huahua Xiao and Michael J Gollner and Elaine S Oran},
url = {https://doi.org/10.1016/j.combustflame.2019.02.018},
doi = {10.1016/j.combustflame.2019.02.018},
issn = {15562921},
year = {2019},
date = {2019-01-01},
journal = {Combustion and Flame},
volume = {203},
pages = {352--361},
publisher = {Elsevier Inc.},
abstract = {The blue whirl is a small flame with an inverted conical shape, first observed as it developed from fire whirls formed using liquid fuels burning on a water surface. Here, it is shown that the water surface is not critical for a transition from a fire whirl to a blue whirl, but that the surface over which the whirl is formed must be flat without any obstructions to the incoming flow. This observation highlights the importance of the radial boundary layer formed at the base of the whirl. The transition therefore also occurs over a flat metal plate, over which temperature maps of blue whirls are obtained using thin-filament pyrometry. Visualization of the reaction front, by imaging spontaneous OH* chemiluminescence, shows that a significant fraction of the combustion occurs in the small, visibly bright, blue ring. The temperature maps are consistent with the burning structure seen with chemiluminescence, and they are qualitatively similar for blue whirls formed over both water and metal plates. High frame-rate images of the transition process show the presence of a recirculation zone within the flame. Together, these observations distinguish the blue whirl as a flame structure unique from the fire whirl and present a basis for understanding the physical processes which control blue whirl formation and its structure.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Tang, Wei; Finney, Mark; McAllister, Sara; Gollner, Michael
An Experimental Study of Intermittent Heating Frequencies From Wind-Driven Flames Journal Article
In: Frontiers in Mechanical Engineering, vol. 5, no. June, pp. 1–9, 2019, ISSN: 2297-3079.
@article{Tang2019,
title = {An Experimental Study of Intermittent Heating Frequencies From Wind-Driven Flames},
author = {Wei Tang and Mark Finney and Sara McAllister and Michael Gollner},
doi = {10.3389/fmech.2019.00034},
issn = {2297-3079},
year = {2019},
date = {2019-01-01},
journal = {Frontiers in Mechanical Engineering},
volume = {5},
number = {June},
pages = {1--9},
abstract = {An experimental study was conducted to understand the intermittent heating behavior downstream of a gaseous line burner under forced flow conditions. While previous studies have addressed time-averaged properties, here measurements of the flame location and intermittent heat flux profile help to give a time-dependent picture of downstream heating from the flame, useful for understanding wind-driven flame spread. Two frequencies are extracted from experiments, the maximum flame forward pulsation frequency in the direction of the wind, which helps describe the motion of the flame, and the local flame-fuel contact frequency in the flame region, which is useful in calculating the actual heat flux that can be received by the unburnt fuel via direct flame contact. The forward pulsation frequency is obtained through video analysis using a variable interval time average (VITA) method. Scaling analysis indicates that the flame forward pulsation frequency varies as a power-law function of the Froude number and fire heat-release rate, . For the local flame-fuel contact frequency, it is found that the non-dimensional flame-fuel contact frequency remains approximately constant before the local Rix reaches 1, e.g., attached flames. When Rixtextgreater1, decreases with local as Rix flames lift up. A piece-wise function was proposed to predict the local flame-fuel contact frequency including the two Rix scenarios. Information from this study helps to shed light on the intermittent behavior of flames under wind, which may be a critical factor in explaining the mechanisms of forward flame spread in wildland and other similar wind-driven fires.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hu, Yu; Hariharan, Sriram Bharath; Qi, Haiying; Gollner, Michael J; Oran, Elaine S
Conditions for formation of the blue whirl Journal Article
In: Combustion and Flame, vol. 205, pp. 147–153, 2019, ISSN: 15562921.
@article{Hu2019,
title = {Conditions for formation of the blue whirl},
author = {Yu Hu and Sriram Bharath Hariharan and Haiying Qi and Michael J Gollner and Elaine S Oran},
doi = {10.1016/j.combustflame.2019.03.043},
issn = {15562921},
year = {2019},
date = {2019-01-01},
journal = {Combustion and Flame},
volume = {205},
pages = {147--153},
abstract = {This paper presents a laboratory study of the relation between blue whirls and fire whirls in terms of circulation (swirl) and energy-release rate. The blue whirl is a small, completely blue, soot-free flame that was originally seen when it evolved from more traditional fire whirls burning liquid hydrocarbons on water. The experimental apparatus consists of two offset quartz half-cylinders suspended over a water surface, with fuel injected onto the water surface from below. The flow circulation is calculated using the diameter of the enclosure and hot-wire velocity measurements made at the inlet gap between the half-cylinders. The heat-release rate was varied by adjusting the volumetric supply rate of liquid n-heptane, and is calculated assuming complete combustion. Results show that stable blue whirls form in a narrow range of circulation and energy-release rate close to a previously cited extinction limit. A scaling law derived from the data, based on the length scale of the enclosure, shows that the transition to a blue whirl depends on the gap size between the half-cylinders of the enclosure.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Ju, Xiaoyu; Gollner, Michael J; Wang, Yiren; Tang, Wei; Zhao, Kun; Ren, Xingyu; Yang, Lizhong
Downstream radiative and convective heating from methane and propane fires with cross wind Journal Article
In: Combustion and Flame, vol. 204, pp. 1 - 12, 2019, ISSN: 0010-2180.
@article{JU20191,
title = {Downstream radiative and convective heating from methane and propane fires with cross wind},
author = {Xiaoyu Ju and Michael J Gollner and Yiren Wang and Wei Tang and Kun Zhao and Xingyu Ren and Lizhong Yang},
url = {http://www.sciencedirect.com/science/article/pii/S0010218019300951},
doi = {https://doi.org/10.1016/j.combustflame.2019.03.001},
issn = {0010-2180},
year = {2019},
date = {2019-01-01},
journal = {Combustion and Flame},
volume = {204},
pages = {1 - 12},
abstract = {Experiments were conducted to elucidate the radiative and convective heating occurring downstream of wind-driven fires produced by a gaseous burner. These flames model, at reduced scale, some of the dynamics observed in wind-driven fire spread through wildlands, buildings, mines or tunnels. Methane and propane were used to create fires ranging from 5 to 25 kW with ambient velocities ranging from 0.6 to 2.2 m/s. The total and incident radiative heat flux to a nearly-adiabatic downstream surface were measured by a water-cooled total heat flux gauge and a radiometer, respectively. The interaction between the buoyancy induced by the flame and momentum from the free stream was represented by a mixed-convection parameter, ξ=Grx2/Rex1n, where n = 3/2, 2 or 5/2. ξ was evaluated with two length scales in order to capture effects of both the boundary layer development length (x1) and heated distance downstream of the burner (x2). Results showed that the propane flame (high luminosity) exhibited slightly higher radiative heat fluxes than methane flames (low luminosity) under the same external conditions, while the convective heat flux followed an opposite trend. The downstream local radiative heat flux was quantified using a dimensionless flame thickness δx*, which showed a good relationship with ξ for n = 5/2 but not 3/2 or 2. The local convective heat transfer coefficient was expressed in the form of a local Nusselt number, Nux2Rex1−1/2, and correlated well as a piecewise function with ξ for n = 5/2. It was found that both δx* and Nux2Rex1−1/2 have a turning point at ξ ≈ 0.005, which was visually shown to denote the location where transition between an attachment and plume-like flame occurs. By separately describing both radiative and convective downstream heating, the mechanisms controlling heating which drives flame spread in wind-driven fires can be further understood.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Pathways for Building Fire Spread in the Wildland Urban Interface
Gollner, M.J., Society of Fire Protection Engineers’ Emerging Trends Newsletter, Issue 101. 2015
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Gollner, M.J., SFPE Emerging Trends Newsletter, Society of Fire Protection Engineers, August, 2015.
The Flammability of a Storage Commodity
Gollner, M.J., Fire Protection Engineering Magazine, Society of Fire Protection Engineers, April 2014.
Effect of Microgravity on the Development and Structure of Fire Whirls
Jones, Michael, M.S. Thesis, University of Maryland College Park, 2020
A STUDY OF INTERMITTENT CONVECTIVE HEATING OF FINE LIVE WILDLAND FUELS
Orcurto, Ashlynne R, M.S. Thesis, Univeristy of Maryland, College Park, 2020
Laboratory Studies on the Generation of Firebrands from Cylindrical Wooden Dowels
Caton, Sara, M.S. Thesis, University of Maryland, College Park, 2017
Thermal Characterization of Firebrand Piles
Hakes, Raquel Sara Pilar, M.S. Thesis, University of Maryland, College Park, 2017
The Structure of the Blue Whirl: A Soot-Free Reacting Vortex Phenomenon
Sriram Bharath Hariharan, M.S. Thesis, University of Maryland, College Park, 2017
Moisture Content Effects on Energy and Emissions Released During Combustion of Pyrophytic Vegetation
Nathaniel Andrew May, M.S. Thesis, University of Maryland, College Park, 2017
A Fundamental Study of Boundary Layer Diffusion Flames
Singh, Ajay. Ph.D. Thesis, University of Maryland, College Park, 2015.
In Situ Burning Alternatives
Cohen, Brian, M.S. Thesis, University of Maryland, College Park, 2014.
Flame Spread Through Wooden Dowels
Zhao, Zhao, M.S. Thesis, University of Maryland, College Park, 2014.
Upward Flame Spread over Discreet Fuels
Miller, Colin, M.S. Thesis, University of Maryland, College Park, 2014
Studying Wildland Fire Spread Using Stationary Burners
Gorham, D.J., M.S. Thesis, University of Maryland, College Park, 2014.
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Towards Data-Driven Operational Wildfire Spread Modeling: A REPORT OF THE NSF-FUNDED WIFIRE WORKSHOP
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Pathways for Building Fire Spread at the Wildland Urban Interface (NFPA Site)
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Literature Review on Hybrid Fire Suppression Systems
Raia, P. and Gollner, M.J., Fire Protection Research Foundation, National Fire Protection Association, May 2014.
Fire Safety Design and Sustainable Buildings: Challenges and Opportunities: Report of a National Symposium
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