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{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{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{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{GOLLNER201768,

title = {The effect of flow and geometry on concurrent flame spread},

author = {Michael J Gollner and Colin H Miller and Wei Tang and Ajay V Singh},

url = {http://www.sciencedirect.com/science/article/pii/S0379711217303454},

doi = {https://doi.org/10.1016/j.firesaf.2017.05.007},

issn = {0379-7112},

year  = {2017},

date = {2017-01-01},

journal = {Fire Safety Journal},

volume = {91},

pages = {68 - 78},

abstract = {Flame spread is an important parameter used in the evaluation of hazards for fire safety applications. The problem of understanding and modeling flame spread has been approached before, however new developments continue to challenge our current view of the subject, necessitating future research efforts in the field. In this review, the problem of flame spread will be revisited, with a particular emphasis on the effect of flow and geometry on concurrent flame spread over solid fuels. The majority of this research is based on that of the senior author, who has worked on wind-driven flame spread, inclined fire spread, flame spread through discrete fuels and the particular problem of wildland fires, where all of the above scenarios play an important role. Recent developments in these areas have improved our understanding of flame-spread processes and will be reviewed, and areas for future research will be highlighted.},

note = {Fire Safety Science: Proceedings of the 12th International Symposium},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Singh2015b,

title = {A methodology for estimation of local heat fluxes in steady laminar boundary layer diffusion flames},

author = {Ajay V Singh and Michael J Gollner},

doi = {10.1016/j.proci.2014.05.040},

issn = {15407489},

year  = {2015},

date = {2015-01-01},

journal = {Combustion and Flame},

volume = {162},

number = {5},

pages = {2214--2230},

abstract = {A thorough numerical and experimental investigation of laminar boundary-layer diffusion flames established over the surface of a condensed fuel is presented. By extension of the Reynold's Analogy, it is hypothesized that the non-dimensional temperature gradient at the surface of a condensed fuel is related to the local mass-burning rate through some constant of proportionality. First, this proportionality is tested by using a validated numerical model for a steady flame established over a condensed fuel surface, under free and forced convective conditions. Second, the relationship is tested by conducting experiments in a free-convective environment (vertical wall) using methanol and ethanol as liquid fuels and PMMA as a solid fuel, where a detailed temperature profile is mapped during steady burning using fine-wire thermocouples mounted to a precision two-axis traverse mechanism. The results from the present study suggests that there is indeed a unique correlation between the mass burning rates of liquid/solid fuels and the temperature gradients at the fuel surface. The correlating factor depends upon the Spalding mass transfer number and gas-phase thermo-physical properties and works in the prediction of both integrated as well as local variations of the mass burning rate as a function of non-dimensional temperature gradient. Additional results from precise measurements of the thermal field are also presented. ?? 2014 The Combustion Institute.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{GOLLNER20132531,

title = {Experimental study of upward flame spread of an inclined fuel surface},

author = {M J Gollner and X Huang and J Cobian and A S Rangwala and F A Williams},

url = {http://www.sciencedirect.com/science/article/pii/S154074891200171X},

doi = {https://doi.org/10.1016/j.proci.2012.06.063},

issn = {1540-7489},

year  = {2013},

date = {2013-01-01},

journal = {Proceedings of the Combustion Institute},

volume = {34},

number = {2},

pages = {2531 - 2538},

keywords = {},

pubstate = {published},

tppubtype = {article}

}