Publications

@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}

}

@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}

}

@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}

}

@article{MCNAMEE2019102889,

title = {IAFSS agenda 2030 for a fire safe world},

author = {Margaret McNamee and Brian Meacham and Patrick van Hees and Luke Bisby and W K Chow and Alexis Coppalle and Ritsu Dobashi and Bogdan Dlugogorski and Rita Fahy and Charles Fleischmann and Jason Floyd and Edwin R Galea and Michael Gollner and Tuula Hakkarainen and Anthony Hamins and Longhua Hu and Peter Johnson and Bj\"{o}rn Karlsson and Bart Merci and Yoshifuni Ohmiya and Guillermo Rein and Arnaud Trouv\'{e} and Yi Wang and Beth Weckman},

url = {http://www.sciencedirect.com/science/article/pii/S0379711219303509},

doi = {https://doi.org/10.1016/j.firesaf.2019.102889},

issn = {0379-7112},

year  = {2019},

date = {2019-01-01},

journal = {Fire Safety Journal},

volume = {110},

pages = {102889},

abstract = {The International Association of Fire Safety Science (IAFSS) is comprised of members from some 40 countries. This paper presents the Association's thinking, developed by the Management Committee, concerning pressing research needs for the coming 10 years presented as the IAFSS Agenda 2030 for a Fire Safe World. The research needs are couched in terms of two broad Societal Grand Challenges: (1) climate change, resiliency and sustainability and (2) population growth, urbanization and globalization. The two Societal Grand Challenges include significant fire safety components, that lead both individually and collectively to the need for a number of fire safety and engineering research activities and actions. The IAFSS has identified a list of areas of research and actions in response to these challenges. The list is not exhaustive, and actions within actions could be defined, but this paper does not attempt to cover all future needs.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Zhao2018,

title = {Experimental and theoretical study on downward flame spread over uninhibited PMMA slabs under different pressure environments},

author = {K Zhao and X Zhou and X Liu and W Tang and M Gollner and F Peng and L Yang},

doi = {10.1016/j.applthermaleng.2018.02.059},

issn = {13594311},

year  = {2018},

date = {2018-01-01},

journal = {Applied Thermal Engineering},

volume = {136},

abstract = {textcopyright 2018 Elsevier Ltd This paper presents an experimental and theoretical study of side-edge effects on downward flame spread over two parallel polymethyl methacrylate (PMMA) slabs under different pressure environments. Identical experiments of downward flame spread over thin PMMA slabs with side-edges unrestrained were conducted at different altitudes in Hefei (102 kPa), Geermu (73.2 kPa) and Lhasa (66.3 kPa). Experimental results show that the flame spread rate is controlled by ignition along the side-edge, rather than at the center of the samples, for experiments with both single and two parallel slabs. Based on these results, a thermal model is developed which describes flame spread along the edge and quantitatively agrees with experimental results. In the parallel-slab case, convective heating appears to influence the spread rate only when the separation distance is very small, with radiative heating playing a more important role as separation distance increases. The angle of the pyrolysis front, formed between the faster side-edge spread and slower center-region spread, hardly changes with pressure, but changes significantly with separation distance, due to differing modes of heat transfer between the side-edge and center region. In addition, variations of flame height with pressure and separation distance are reasonably interpreted from diffusion flame theory.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Miller2018,

title = {Boundary layer instabilities in mixed convection and diffusion flames with an unheated starting length},

author = {Colin H Miller and Wei Tang and Evan Sluder and Mark A Finney and Sara S McAllister and Jason M Forthofer and Michael J Gollner},

url = {https://doi.org/10.1016/j.ijheatmasstransfer.2017.11.040},

doi = {10.1016/j.ijheatmasstransfer.2017.11.040},

issn = {00179310},

year  = {2018},

date = {2018-01-01},

journal = {International Journal of Heat and Mass Transfer},

volume = {118},

pages = {1243--1256},

publisher = {Elsevier Ltd},

abstract = {The following study examines the role of streaklike coherent structures in mixed convection via a horizontal heated boundary layer possessing an unheated starting length. The three-dimensionality of flows in this configuration, which is regularly encountered in practical scenarios, has been experimentally probed using non-invasive detection methods. Experiments were conducted in a wind tunnel at the Missoula Fire Sciences Lab, and the wind speed was varied from 0.70 to 2.47 m/s. The buoyant source was varied significantly by either manipulating the surface temperature of a downstream hot plate or employing a diffusion flame. Streaks were visualized in the flow by means of infrared imaging or high speed video, and a novel detection algorithm was developed to quantify important properties and to spatially track these structures over time. Lognormal distributions of spacing were observed initially, and gradual deviations from this fit indicated a deviation from streaklike behavior. The onset of streaks was determined to be controlled by the pre-existing disturbances populating the incoming boundary layer. Further downstream, buoyant forces dominated the growth and deformation of these structures, whose length scale increased significantly. The width of structures was observed to asymptote to a stable value downstream, and this was determined to be a consequence of the finite distance over which heating was applied.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Miller2018a,

title = {Boundary layer instabilities in mixed convection and diffusion flames with an unheated starting length},

author = {C H Miller and W Tang and E Sluder and M A Finney and S S McAllister and J M Forthofer and M J Gollner},

doi = {10.1016/j.ijheatmasstransfer.2017.11.040},

issn = {00179310},

year  = {2018},

date = {2018-01-01},

journal = {International Journal of Heat and Mass Transfer},

volume = {118},

abstract = {textcopyright 2017 The following study examines the role of streaklike coherent structures in mixed convection via a horizontal heated boundary layer possessing an unheated starting length. The three-dimensionality of flows in this configuration, which is regularly encountered in practical scenarios, has been experimentally probed using non-invasive detection methods. Experiments were conducted in a wind tunnel at the Missoula Fire Sciences Lab, and the wind speed was varied from 0.70 to 2.47 m/s. The buoyant source was varied significantly by either manipulating the surface temperature of a downstream hot plate or employing a diffusion flame. Streaks were visualized in the flow by means of infrared imaging or high speed video, and a novel detection algorithm was developed to quantify important properties and to spatially track these structures over time. Lognormal distributions of spacing were observed initially, and gradual deviations from this fit indicated a deviation from streaklike behavior. The onset of streaks was determined to be controlled by the pre-existing disturbances populating the incoming boundary layer. Further downstream, buoyant forces dominated the growth and deformation of these structures, whose length scale increased significantly. The width of structures was observed to asymptote to a stable value downstream, and this was determined to be a consequence of the finite distance over which heating was applied.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jiang2018,

title = {Flame spread and burning rates through vertical arrays of wooden dowels},

author = {Lin Jiang and Zhao Zhao and Wei Tang and Colin Miller and Jin Hua Sun and Michael J Gollner},

doi = {10.1016/j.proci.2018.09.008},

issn = {15407489},

year  = {2018},

date = {2018-01-01},

journal = {Proceedings of the Combustion Institute},

volume = {000},

pages = {1--8},

publisher = {Elsevier Inc.},

abstract = {Fuel loads in real-world fire scenarios often feature discrete elements, discontinuities, or inhomogeneities; however, most models for flame spread only assume a continuous, homogeneous fuel. Because discrete fuels represent a realistic scenario not yet well-modeled, it is of interest to find simple methods to model fire growth first in simple, laboratory-scale configurations. A detailed experimental and theoretical study was therefore performed to investigate the controlling mechanisms of flame spread through arrays of wooden dowels, with dowel spacings of 0.75, 0.875, and 1.5 cm. Flames were found to spread vertically for all spacings; however, for the 1.5 cm spacing, the gap was too large for horizontal flame spread to occur. A radiation-controlled model for horizontal flame spread was developed that predicted the horizontal flame spread rate through various arrays of dowels. Combined with an existing convection-based model for vertical flame spread, both horizontal and vertical flame spread was modeled to predict the number of burning wooden dowels as a function of time. Using models for the burning rate of wooden dowels and boundary-layer theory, a global burning rate model was developed that provided reasonable agreement with experimental results.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Manzello2018,

title = {Summary of workshop large outdoor fires and the built environment},

author = {Samuel L Manzello and Raphaele Blanchi and Michael J Gollner and Daniel Gorham and Sara McAllister and Elsa Pastor and Eul{\`{a}}lia Planas and Pedro Reszka and Sayaka Suzuki},

url = {https://doi.org/10.1016/j.firesaf.2018.07.002},

doi = {10.1016/j.firesaf.2018.07.002},

issn = {03797112},

year  = {2018},

date = {2018-01-01},

journal = {Fire Safety Journal},

volume = {100},

number = {December 2017},

pages = {76--92},

publisher = {Elsevier Ltd},

abstract = {Large outdoor fires present a risk to the built environment. Wildfires that spread into communities, referred to as Wildland-Urban Interface (WUI) fires, have destroyed communities throughout the world, and are an emerging problem in fire safety science. Other examples are large urban fires including those that have occurred after earthquakes. Research into large outdoor fires, and how to potentially mitigate the loss of structures in such fires, lags other areas of fire safety science research. At the same time, common characteristics between fire spread in WUI fires and urban fires have not been fully exploited. In this paper, an overview of the large outdoor fire risk to the built environment from each region is presented. Critical research needs for this problem in the context of fire safety science are provided. The present paper seeks to develop the foundation for an international research needs roadmap to reduce the risk of large outdoor fires to the built environment.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Tohidi2018,

title = {Fire Whirls},

author = {Ali Tohidi and Michael J Gollner and Huahua Xiao},

doi = {10.1146/annurev-fluid-122316-045209},

issn = {0066-4189},

year  = {2018},

date = {2018-01-01},

journal = {Annual Review of Fluid Mechanics},

volume = {50},

number = {1},

pages = {187--213},

abstract = {Fire whirls present a powerful intensification of combustion, long studied in the fire research community because of the dangers they present during large urban and wildland fires. However, their destructive power has hidden many features of their formation, growth, and propagation. Therefore, most of what is known about fire whirls comes from scale modeling experiments in the laboratory. Both the methods of formation, which are dominated by wind and geometry, and the inner structure of the whirl, including velocity and temperature fields, have been studied at this scale. Quasi-steady fire whirls directly over a fuel source form the bulk of current experimental knowledge, although many other cases exist in nature. The structure of fire whirls has yet to be reliably measured at large scales; however, scaling laws have been relatively successful in modeling the conditions for formation from small to large scales. This review surveys the state of knowledge concerning the fluid dynamics of fire whirls, including the conditions for their formation, their structure, and the mechanisms that control their unique state. We highlight recent discoveries and survey potential avenues for future research, including using the properties of fire whirls for efficient remediation and energy generation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{BROWN20181,

title = {Proceedings of the first workshop organized by the IAFSS Working Group on Measurement and Computation of Fire Phenomena (MaCFP)},

url = {http://www.sciencedirect.com/science/article/pii/S0379711218301814},

doi = {https://doi.org/10.1016/j.firesaf.2018.08.009},

issn = {0379-7112},

year  = {2018},

date = {2018-01-01},

journal = {Fire Safety Journal},

volume = {101},

pages = {1 - 17},

abstract = {This paper provides a report of the discussions held at the first workshop on Measurement and Computation of Fire Phenomena (MaCFP) on June 10\textendash11 2017. The first MaCFP workshop was both a technical meeting for the gas phase subgroup and a planning meeting for the condensed phase subgroup. The gas phase subgroup reported on a first suite of experimental-computational comparisons corresponding to an initial list of target experiments. The initial list of target experiments identifies a series of benchmark configurations with databases deemed suitable for validation of fire models based on a Computational Fluid Dynamics approach. The simulations presented at the first MaCFP workshop feature fine grid resolution at the millimeter- or centimeter-scale: these simulations allow an evaluation of the performance of fire models under high-resolution conditions in which the impact of numerical errors is reduced and many of the discrepancies between experimental data and computational results may be attributed to modeling errors. The experimental-computational comparisons are archived on the MaCFP repository [1]. Furthermore, the condensed phase subgroup presented a review of the main issues associated with measurements and modeling of pyrolysis phenomena. Overall, the first workshop provided an illustration of the potential of MaCFP in providing a response to the general need for greater levels of integration and coordination in fire research, and specifically to the particular needs of model validation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Caton2016a,

title = {Review of Pathways for Building Fire Spread in the Wildland Urban Interface Part I: Exposure Conditions},

author = {Sara E Caton and Raquel S P Hakes and Daniel J Gorham and Aixi Zhou and Michael J Gollner},

url = {http://link.springer.com/10.1007/s10694-016-0589-z},

doi = {10.1007/s10694-016-0589-z},

issn = {0015-2684},

year  = {2017},

date = {2017-03-01},

journal = {Fire Technology},

volume = {53},

number = {2},

pages = {429--473},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Tang2017,

title = {An experimental study on the intermittent extension of flames in wind-driven fires},

author = {W Tang and D J Gorham and M A Finney and S Mcallister and J Cohen and J Forthofer and M J Gollner},

doi = {10.1016/j.firesaf.2017.03.030},

issn = {03797112},

year  = {2017},

date = {2017-01-01},

journal = {Fire Safety Journal},

volume = {91},

abstract = {textcopyright 2017 Elsevier Ltd Experiments were conducted to study the intermittent extension of flames from wind-driven line fires using stationary burners. These fires are thought to share similar features with propagating wildland fires, where forward pulsations of flame have been observed to quickly ignite material far ahead of the mean flame front. However, stationary burners offer the ability to study the movement of the flame and its heating processes in greater detail than a spreading fire. In these stationary experiments, propane gas was used as a fuel with different burner sizes, 25\textendash30 cm wide and 5\textendash25 cm long in the direction of the flow. A specially-built wind tunnel was used to provide a well-characterized laminar flow for the experimental area. The free-stream flow velocity, measured by a hot-wire anemometer, ranged in the experiments from 0.2 to 2.7 m/s. The shape of the flame was measured using a high-speed video camera mounted perpendicular to the apparatus. A method was developed to track the extension of the flame close to the surface, simulating flame contact with unburnt fuel downstream of the fire. This extension length was then measured frame by frame and frequencies of flame presence/absence determined as a function of downstream distance. The location of maximum pulsation frequency, x max , for each burner/wind configuration, was obtained using a level-crossing approach (essentially the variable-interval time-average (VITA) method). Further study indicates that x max can be well estimated using mean flame properties. Probability distributions describing the location of the flame over time also showed that, the probability the flame extends far beyond the mean flame front is sensitive to increasing ambient winds and fire size.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jiang2017,

title = {Sample width and thickness effects on horizontal flame spread over a thin PMMA surface},

author = {L Jiang and C H Miller and M J Gollner and J -H Sun},

doi = {10.1016/j.proci.2016.06.157},

issn = {15407489},

year  = {2017},

date = {2017-01-01},

journal = {Proceedings of the Combustion Institute},

volume = {36},

number = {2},

abstract = {textcopyright 2016 Elsevier Ltd. In previous studies, it was found that there exists a minimum flame spread rate under a certain range of sample widths for steady burning horizontal flame spread. While this was hypothesized to occur due to a transition between convectively-dominated to radiation-dominated flame spread, no measurements were performed to quantify this process. This paper presents a detailed experimental study investigating sample width and thickness effects on steady horizontal flame spread, including detailed measurements of the components of radiation, convection, and conduction. Water-cooled heat flux gauges, R-type micro-thermocouples traversed through the gas phase, and K-type thermocouples embedded in the solid phase were all used to deduce these heat transfer components. Results show that convective heat transfer decreases with increasing sample width as the shape of the flame front is on average farther from the fuel surface, while radiation increases as the view factor from the fire to unignited fuel increases with larger sample size. Conduction measured within the fuel sample is, as expected, confirmed to be negligible. Comparing a combination of these components, the total heat flux first decreases as the competition between radiation and convection changes, followed by steadily increasing heat fluxes as the width of the sample increases. Heat feedback also influences the sample pyrolysis rate, so there was a coupled response following this trend. The apparent dip followed by an increase in total heat flux can now explain why a period of minimum flame spread rate exists. Modification of an existing theory also matches experimental results very closely. Finally, a dimensionless heat-release rate for different sample configurations is used to scale the dimensionless flame heights with a power-law correlation having exponents 0.39 for Q∗ textgreater 1 and 0.6 for Q∗ textless 1, closely resembling the 2/5 and 2/3 predicted by Zukoski's model.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Tang2017a,

title = {Local flame attachment and heat fluxes in wind-driven line fires},

author = {W Tang and C H Miller and M J Gollner},

doi = {10.1016/j.proci.2016.06.064},

issn = {15407489},

year  = {2017},

date = {2017-01-01},

journal = {Proceedings of the Combustion Institute},

volume = {36},

number = {2},

abstract = {textcopyright 2016 by The Combustion Institute. Published by Elsevier Inc. A detailed experimental investigation of turbulent diffusion flames under forced flow was conducted to study local heat fluxes to a nearly adiabatic surface downstream of a gaseous line burner. A variety of ambient wind velocities and fuel flow rates were employed to study different fire scenarios modeling the dynamics of wind-driven fire spread as found in wildland, mine or tunnel fires. The downstream heat flux distribution was correlated as a piecewise function with the Richardson number in two regimes, the first with higher heat fluxes, where the flame remained attached the downstream surface (attached region) and the second with a steeper decay of heat fluxes (plume region). Analysis of the heat flux distribution revealed that local heat fluxes roughly reach a maximum where the Richardson number equaled unity. This was thought to be a good marker of the regime where the flame detaches from the surface, e.g. where buoyancy from the flame overcomes inertial forces from the oncoming flow. This observation was further corroborated by analysis of side-view images of the flame, which showed the attachment location was linearly correlated with the location where the Richardson number equaled unity. The results from this study suggest that local heat flux values reach a maximum at the transition between a momentum-dominated (attached, wind-driven) to buoyancy-dominated (plume or fire) regime in forced flow scenarios. The results have interesting implications to the problem of flame attachment, which is known to accelerate fire spread in both inclined and wind-driven fire scenarios.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Miller2017,

title = {Investigating coherent streaks in wildfires via heated plates in crosswind},

author = {C Miller and M A Finney and S McAllister and E Sluder and M J Gollner},

doi = {10.1016/j.firesaf.2017.03.035},

issn = {03797112},

year  = {2017},

date = {2017-01-01},

journal = {Fire Safety Journal},

volume = {91},

abstract = {textcopyright 2017 Elsevier Ltd Streaklike coherent structures are consistently observed in boundary layer flames, but their role in modifying heat and mass transfer remains unknown. In the following experiment, a non-reactive thermal plume was employed to study analogous streaks in an environment where the local source of buoyancy could be directly modified. A horizontal hot plate was exposed to crossflow, and infrared thermography was successfully employed to capture thermal traces of streaks on the surface. Post-processing of surface temperature data enabled the quantification of important properties of streaks, such as location, spacing, width, and strength. The distribution of streak spacing was found to have a lognormal distribution. Mean streak spacing and width increased with downstream distance, indicating the amplification and aggregation of coherent structures. Streak spacing decreased when either the hot plate temperature increased from 150 °C to 300 °C or the wind speed increased from 0.5 to 1.2 m/s. Streaks were seen to modify the spanwise distribution of heat transfer to the surface, most notably when the hot plate temperature was increased from 150 °C to 300 °C.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Singh2017,

title = {Steady and transient pyrolysis of a non-charring solid fuel under forced flow},

author = {A V Singh and M J Gollner},

doi = {10.1016/j.proci.2016.07.043},

issn = {15407489},

year  = {2017},

date = {2017-01-01},

journal = {Proceedings of the Combustion Institute},

volume = {36},

number = {2},

abstract = {textcopyright 2016 by The Combustion Institute. Published by Elsevier Inc. In previous work, the Reynolds analogy was used to develop a theoretical expression that allowed for the estimation of local mass burning rates in steady laminar boundary layer diffusion flames established over liquid and solid fuels. This technique was used to elucidate the mechanisms responsible for pyrolysis of both solid and liquid fuels in forced and free convective environments. These previous studies, however, focused on steady results that occur early in the combustion process, before regression of the fuel surface begins to influence results. In this work, a thorough experimental investigation of steady and transient pyrolysis of clear cast Poly Methyl Methacrylate (PMMA) is presented using both local pyrolysis rates and heat feedback to the condensed fuel surface measured at different streamwise locations in a bench-scale wind tunnel. A functional form of the Nusselt number is derived that can be readily used to identify these steady and transient regimes of PMMA burning in the form of local convective heat transfer coefficients. At early times ( textless 150 s), a steady burning regime is identified where heat feedback properties are constant and the gas phase can be assumed to be in a steady state. At later times, a transient burning regime dominated by solid-phase effects occurs. Heat feedback from the flame and hence local mass loss rates measured at later times are transient in nature and do not correspond well with the steady state theoretical solution. Investigation under different forced-flow wind conditions reveals this transient phenomena most likely occurs due to both deformation of the surface of PMMA and solid-phase conduction into the fuel, which eventually influences the gas phase. The results presented will be useful for future modeling of transient solid-phase combustion, especially as it is applied to studies of flame spread.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hariharan2017,

title = {The Structure of the Blue Whirl},

author = {S B Hariharan and Y Hu and H Xiao and M J Gollner and Elaine S Oran},

url = {http://meetings.aps.org/link/BAPS.2017.DFD.D35.3},

doi = {10.1016/j.proci.2018.05.115},

issn = {1540-7489},

year  = {2017},

date = {2017-01-01},

journal = {70th Annual Meeting of the APS Division of Fluid Dynamics},

volume = {000},

pages = {1--9},

abstract = {Recent experiments have led to the discovery of the blue whirl, a small, stable regime of the fire whirl that burns typically sooty liquid hydrocarbons without producing soot. The physical structure consists of three regions -- the blue cone, the vortex rim and the purple haze. The physical nature of the flame was further investigated through digital imaging techniques, which suggest that the transition (from the fire whirl to the blue whirl) and shape of the flame may be influenced by vortex breakdown. The flame was found to develop over a variety of surfaces, which indicates that the formation of the blue whirl is strongly influenced by the flow structure over the incoming boundary layer. The thermal structure was investigated using micro-thermocouples, thin-filament pyrometry and OH* spectroscopy. These revealed a peak temperature around 2000 K, and that most of the combustion occurs in the relatively small, visibly bright vortex rim. The results of these investigations provide a platform to develop a theory on the structure of the blue whirl, a deeper understanding of which may affirm potential for applications in the energy industry. *This work was supported by an NSF EAGER award and Minta Martin Endowment Funds in the Department of Aerospace Engineering at the University of Maryland.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hall2017,

title = {A Survey of Transient Fire Load on Passenger Ferry Vessels},

author = {Brian M Hall and Michael J Gollner},

doi = {10.1007/s10694-016-0629-8},

issn = {15728099},

year  = {2017},

date = {2017-01-01},

journal = {Fire Technology},

volume = {53},

number = {3},

pages = {1471--1478},

publisher = {Springer US},

abstract = {Aluminum ferries in the United States are unique in that they have policy requirements limiting the weight of luggage carried per fixed passenger seat, which is accomplished by controlling the weight of baggage per passenger, but no means to enforce this requirement. A survey of passenger ferry vessels was performed to determine the type of baggage loading present in these passenger compartments. The type, carriage rate, and weight were recorded to determine the transient fire load as well as the average weight of luggage brought on board. The average baggage weight for the commuter vs. non-commuter ferries surveyed in this study were found to be 2.8 and 3.7 kg per person, respectively. These numbers are in close agreement with the average weight per person calculated for carriage on trains. Survey data indicates that the current average baggage weight of 3.7 kg exceeds that allowed by Coast Guard policy for 93% of vessels, with the remaining 7% falling within the policy requirements due to unusually low seat density in the main passenger compartment. This highlights a potential pitfall in current regulatory standards that may present a mismatch for performance and prescriptive based requirements. As few baggage surveys have been conducted on commuter vessels, this data which includes both number and weight distributions per baggage type may also be useful for transient fire load calculations in the future.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{caton2017review,

title = {Review of pathways for building fire spread in the wildland urban interface part I: exposure conditions},

author = {Sara E Caton and Raquel SP Hakes and Daniel J Gorham and Aixi Zhou and Michael J Gollner},

year  = {2017},

date = {2017-01-01},

journal = {Fire technology},

volume = {53},

number = {2},

pages = {429--473},

publisher = {Springer},

keywords = {},

pubstate = {published},

tppubtype = {article}

}