Wind Tunnel Experiments to Study Chaparral Crown Fires

Cobian-Iñiguez, Jeanette; Aminfar, AmirHessam; Chong, Joey; Burke, Gloria M.; Zuniga, Albertina; Weise, David R.; Princevac, Marko

doi:10.3791/56591

Cited by 3 publications

(2 citation statements)

References 18 publications

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“…branches and foliage harvested locally. Custom instrumentation was developed to measure mass loss from the crown fuel layer; full details of this system can be found in Cobian-Iñiguez et al (2017). Surface fuel mass loss was measured using an electronic scale placed under a portion of the excelsior fuel bed.…”

Section: Methodology Experimentalmentioning

confidence: 99%

On the Use of Semi-empirical Flame Models for Spreading Chaparral Crown Fire

et al. 2019

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Flame geometry plays a key role in shaping fire behavior as it can influence flame spread, radiative heat transfer and fire intensity. For wildland fire, thorough characterizations of flame geometry can help advance the derivation of comprehensive models of wildfire behavior. Within the fire community, a classical flame modeling approach has been to develop semi-empirical models. Many of these models have been derived for surface fuels or for pool fire configurations. However, few have sought to model flame behavior in chaparral crown fires. Thus, the objective of this study is to assess the applicability of semi-empirical models on observed chaparral crown fire behavior. Semi-empirical models of flame tilt, flame height, and flame length from the literature are considered. Comparison with experimental observation of flame height in the crown fuel layer, showed good agreement between the 2/5th power law that relates flame height to heat release rate. Two new power-law correlations relating flame tilt angle to Froude number are proposed. The coefficients for new models are obtained from regression analysis.

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Section: Methodology Experimentalmentioning

confidence: 99%

On the Use of Semi-empirical Flame Models for Spreading Chaparral Crown Fire

et al. 2019

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“…However, for these undisturbed fuel beds, the flame front generated was not homogeneous (litter mass varying from one sample to another and its composition being heterogeneous when collected undisturbed; see Ganteaume et al 2016). The excelsior fuel bed allowed a simplification in both experiments and modelling and is regularly used to model surface fuel in burning experiments (Dickinson et al 2013;Cobian-Iñiguez et al 2017). This fuel is highly flammable and the flame front is more constant during the burning process than with the undisturbed litter bed.…”

Section: Excelsior Fuel Bedmentioning

confidence: 99%

Modelling the fire propagation from the fuel bed to the lower canopy of ornamental species used in wildland–urban interfaces

Terrei¹,

Lamorlette²,

Ganteaume³

2019

Int. J. Wildland Fire

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South-eastern France is strongly affected by wildfires mostly occurring in the wildland–urban interfaces (WUIs). A WUI fire is often initiated in dead surface fuel, then can propagate to shrubs and trees when the lower canopy is close to (or touches) the ground. Whereas a previous study assessed the fire propagation from the fuel bed to the lower canopy of different species used as ornamental vegetation in this region, the objectives of the current work consisted of checking if the modelling of this fire propagation was possible using WFDS (Wildland–Urban Interface Fire Dynamical Simulator) in comparing experimental and modelling results. Experimental and modelling constraints (i.e. branch geometric definition, branch motion due to convection) showed differences in some of the recorded data (such as time to ignition, ignition temperature, mass loss and maximum temperature), but comparisons of variation in mass loss and temperature over time showed that modelling the fire propagation at the scale of a branch was possible if the branch fuel-moisture content remained lower than 25%. For both experiments and modelling, the ranking of species according to their branch flammability highlighted identical groups of species.

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Using Background-Oriented Schlieren to Visualize Convection in a Propagating Wildland Fire

Aminfar

Cobian-Iñiguez

Ghasemian

et al. 2019

Combustion Science and Technology

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Heat and mass transfer are important processes associated with wildland fire. Both radiant and convective heat transfer are important processes with convection often being the dominant mechanism. Unlike radiation, there is no direct method of measuring convection. Since convective heat transfer is governed by the fluid flow, understanding the fluid flow provides good understanding on the convective heat transfer. In fluid mechanics, flow visualization is a common methodology used to understand flow characteristics. Schlieren imagery is a common flow visualization technique which captures changes in fluid density such as the ones occur around a fire. Background-Oriented Schlieren (BOS) is a flow visualization technique that uses a background image with various patterns to visualize the density gradient caused by density fluctuations in a fluid. We applied BOS to measure the flow associated with laboratory-scale line fires. The reproducible fires were spreading in pine needle fuel beds in a wind tunnel with and without imposed wind. This initial application of BOS in a fire environment successfully visualized the flow around the flame. The visualized flow underwent a secondary process to produce the velocity field of the flow. Results indicate that even in conditions where the fire is known to be dominated by radiation, wind carried the thermal plume ahead of the flame front and expanded the thermal plume. In contrast, in the no wind condition, the thermal plume remained vertical above the fire. Using the BOS imagery, a new model for estimation of convective heat transfer was introduced. In addition to estimation of the convective heat transfer ahead of the fire, this new model enables visualization of convective motion.

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Wind Tunnel Experiments to Study Chaparral Crown Fires

Cited by 3 publications

References 18 publications

On the Use of Semi-empirical Flame Models for Spreading Chaparral Crown Fire

On the Use of Semi-empirical Flame Models for Spreading Chaparral Crown Fire

Modelling the fire propagation from the fuel bed to the lower canopy of ornamental species used in wildland–urban interfaces

Using Background-Oriented Schlieren to Visualize Convection in a Propagating Wildland Fire

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