Feasibility of particle image velocimetry in vegetative fire spread experiments

Morandini, Frédéric; Silvani, Xavier; Susset, Arnaud

doi:10.1007/s00348-012-1285-5

Cited by 11 publications

(12 citation statements)

References 16 publications

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“…The term has roots in the meteorological literature (e.g., [ 6 ]) while it is often referred to as convective or advective flux in the engineering literature (e.g., [ 7 , 8 ]). Based on flow velocities and gas temperatures, sensible heat fluxes in wildland fires have been measured using videography [ 9 , 10 ], particle velocimetry [ 11 , 12 ], one-dimensional anemometry [ 13 , 14 ], and two- and three-dimensional anemometry [ 15 , 16 , 17 ]. Sensible heat flux and energy have not been estimated in or just above wildland fire flames because instrumentation has not been sufficiently fire-hardened [ 18 , 19 ].…”

Section: Introductionmentioning

confidence: 99%

The Wildland Fire Heat Budget—Using Bi-Directional Probes to Measure Sensible Heat Flux and Energy in Surface Fires

Dickinson

Wold

Butler

et al. 2021

Sensors

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Sensible energy is the primary mode of heat dissipation from combustion in wildland surface fires. However, despite its importance to fire dynamics, smoke transport, and in determining ecological effects, it is not routinely measured. McCaffrey and Heskestad (A robust bidirectional low-velocity probe for flame and fire application. Combustion and Flame 26:125–127, 1976.) describe measurements of flame velocity from a bi-directional probe which, when combined with gas temperature measurements, can be used to estimate sensible heat fluxes. In this first field application of bi-directional probes, we describe vertical and horizontal sensible heat fluxes during the RxCADRE experimental surface fires in longleaf pine savanna and open ranges at Eglin Air Force Base, Florida. Flame-front sensible energy is the time-integral of heat flux over a residence time, here defined by the rise in gas temperatures above ambient. Horizontal flow velocities and energies were larger than vertical velocities and energies. Sensible heat flux and energy measurements were coordinated with overhead radiometer measurements from which we estimated fire energy (total energy generated by combustion) under the assumption that 17% of fire energy is radiated. In approximation, horizontal, vertical, and resultant sensible energies averaged 75%, 54%, and 64%, respectively, of fire energy. While promising, measurement challenges remain, including obtaining accurate gas and velocity measurements and capturing three-dimensional flow in the field.

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Section: Introductionmentioning

confidence: 99%

The Wildland Fire Heat Budget—Using Bi-Directional Probes to Measure Sensible Heat Flux and Energy in Surface Fires

Dickinson

Wold

Butler

et al. 2021

Sensors

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“…They also provide errors, but they do not provide statistical distributions of their data. Morandini et al [14] implemented particle image velocimetry (PIV) to develop techniques to measure the turbulent wind velocities in and around a fire with video camera mounted on the ground. Their initial results show the dependence of flow within the fire on the buoyancy regime, with transitions from strong vertical to horizontal flow.…”

Section: Introductionmentioning

confidence: 99%

Fine-Scale Fire Spread in Pine Straw

Sagel

Speer

Pokswinski

et al. 2021

Fire

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Most wildland and prescribed fire spread occurs through ground fuels, and the rate of spread (RoS) in such environments is often summarized with empirical models that assume uniform environmental conditions and produce a unique RoS. On the other hand, representing the effects of local, small-scale variations of fuel and wind experienced in the field is challenging and, for landscape-scale models, impractical. Moreover, the level of uncertainty associated with characterizing RoS and flame dynamics in the presence of turbulent flow demonstrates the need for further understanding of fire dynamics at small scales in realistic settings. This work describes adapted computer vision techniques used to form fine-scale measurements of the spatially and temporally varying RoS in a natural setting. These algorithms are applied to infrared and visible images of a small-scale prescribed burn of a quasi-homogeneous pine needle bed under stationary wind conditions. A large number of distinct fire front displacements are then used statistically to analyze the fire spread. We find that the fine-scale forward RoS is characterized by an exponential distribution, suggesting a model for fire spread as a random process at this scale.

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“…Optical methods such as Particle Image Velocimetry (PIV) have been performed to quantify the local velocity field and flow structure of the fire environment (Lozano et al 2010;Maynard and Princevac 2012;Maynard, Princevac, Weise 2016;Morandini, Silvani, Susset 2012;Mungal, Lourenco, Krothpalli 1995). The information provided by PIV is limited to the velocity field so it cannot provide a complete picture of thermal convection because the temperature is not measured.…”

Section: Introductionmentioning

confidence: 99%

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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Feasibility of particle image velocimetry in vegetative fire spread experiments

Cited by 11 publications

References 16 publications

The Wildland Fire Heat Budget—Using Bi-Directional Probes to Measure Sensible Heat Flux and Energy in Surface Fires

The Wildland Fire Heat Budget—Using Bi-Directional Probes to Measure Sensible Heat Flux and Energy in Surface Fires

Fine-Scale Fire Spread in Pine Straw

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

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