Re-analysis of wind and slope effects on flame characteristics of Mediterranean shrub fires
Ralph M. NelsonUSDA Forest Service, 206 Morning View Way, Leland, NC 28451, USA. [Retired] Email: nelsonsally42@gmail.com
International Journal of Wildland Fire 24(7) 1001-1007 https://doi.org/10.1071/WF14155
Submitted: 4 September 2014 Accepted: 25 June 2015 Published: 25 August 2015
Abstract
During the past 20 years, study of wind–slope-aided wildland fire behaviour with experimental burns and physical modelling methods has increased. As part of their continuing study of fires in Mediterranean shrub, F. Morandini and X. Silvani reported experimental temperatures, heat fluxes, flame characteristics and other fire behaviour variables measured on five wind–slope-aided fires. Calculating convection numbers and several convective Froude numbers, the authors concluded that these dimensionless variables for their two wind-dominated fires did not satisfy criteria identified in previous studies for determining mechanisms of heat transfer during fuel preheating. The present paper describes a re-analysis of the data based on a triangular flame model and alternative definitions of flame tilt angle and height. This new analysis has shown that the influence of slope on the fire behaviour was not accounted for; thus, the conclusion of Morandini and Silvani is questionable. Of the five dimensionless variables studied using criteria in the literature, the squared flame height convective Froude number best describes modes of heat transfer to unburned fuels during the experimental fires. Though these results come indirectly from field measurements, they confirm the need to include slope effects in descriptions of wind–slope-aided fire behaviour.
Additional keywords: buoyant and inertial forces, convection number, flame height, length and tilt angle, Froude and convective Froude numbers, radiative and convective heat transfer, triangular flame model.
References
Anderson W, Pastor E, Butler B, Catchpole E, Dupuy JL, Fernandes P, Guijarro M, Mendes-Lopes JM, Ventura J (2006) Evaluating models to estimate flame characteristics for free-burning fires using laboratory and field data. In ‘Proceedings, V international conference on forest fire research’, 27–30 November 2006, Figueira da Foz, Portugal. (Ed. DX Viegas). (CD-ROM) (Elsevier BV: Amsterdam)Balbi JH, Rossi JL, Marcelli T, Santoni PA (2007) A 3D physical real-time model of surface fire across fuel beds. Combustion Science and Technology 179, 2511–2537.
| A 3D physical real-time model of surface fire across fuel beds.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2sXht1ShtbrI&md5=7ba93d397aab4c260073dda17b7d1054CAS |
Balbi JH, Rossi JL, Thierry M, Chatelon FJ (2010) Physical modeling of surface fire under non-parallel wind and slope conditions. Combustion Science and Technology 182, 922–939.
| Physical modeling of surface fire under non-parallel wind and slope conditions.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXosFCrtrs%3D&md5=13ef339a458aa60ec8a7b2b66ac57808CAS |
Boboulos M, Purvis MRI (2009) Wind and slope effects on ROS during the fire propagation in east-Mediterranean pine forest litter. Fire Safety Journal 44, 764–769.
| Wind and slope effects on ROS during the fire propagation in east-Mediterranean pine forest litter.Crossref | GoogleScholarGoogle Scholar |
Clark TL, Jenkins MA, Coen J, Packham DR (1996) A coupled atmospheric–fire model: role of the convective Froude number and dynamic fingering at the fire line. International Journal of Wildland Fire 6, 177–190.
| A coupled atmospheric–fire model: role of the convective Froude number and dynamic fingering at the fire line.Crossref | GoogleScholarGoogle Scholar |
Fernandes PM, Botelho HS, Rego FC, Loureiro C (2009) Empirical modeling of surface fire behavior in maritime pine stands. International Journal of Wildland Fire 18, 698–710.
| Empirical modeling of surface fire behavior in maritime pine stands.Crossref | GoogleScholarGoogle Scholar |
Frankman D, Webb BW, Butler BW, Jimenez D, Forthofer JM, Sopko P, Shannon KS, Hiers JK, Ottmar RD (2013) Measurements of convective and radiative heating in wildland fires. International Journal of Wildland Fire 22, 157–167.
| Measurements of convective and radiative heating in wildland fires.Crossref | GoogleScholarGoogle Scholar |
Linn R, Wintercamp J, Edminster C, Colman JJ, Smith WS (2007) Coupled influences of topography and wind on wildland fire behaviour. International Journal of Wildland Fire 16, 183–195.
| Coupled influences of topography and wind on wildland fire behaviour.Crossref | GoogleScholarGoogle Scholar |
Morandini F, Silvani X (2010) Experimental investigation of the physical mechanisms governing the spread of wildfires. International Journal of Wildland Fire 19, 570–582.
| Experimental investigation of the physical mechanisms governing the spread of wildfires.Crossref | GoogleScholarGoogle Scholar |
Morandini F, Santoni PA, Balbi JH (2001) The contribution of radiant heat transfer to laboratory-scale fire spread under the influences of wind and slope. Fire Safety Journal 36, 519–543.
| The contribution of radiant heat transfer to laboratory-scale fire spread under the influences of wind and slope.Crossref | GoogleScholarGoogle Scholar |
Morandini F, Simeoni A, Santoni PA, Balbi JH (2005) A model for the spread of fire across a fuel bed incorporating the effect of wind and slope. Combustion Science and Technology 177, 1381–1418.
| A model for the spread of fire across a fuel bed incorporating the effect of wind and slope.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2MXlvVSmsrc%3D&md5=fb18f35c60d0897595e4c9eec51ad44fCAS |
Morvan D, Dupuy JL (2004) Modeling the propagation of a wildfire through a Mediterranean shrub using a multiphase formulation. Combustion and Flame 138, 199–210.
| Modeling the propagation of a wildfire through a Mediterranean shrub using a multiphase formulation.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXmtlOrurc%3D&md5=3fa78e615863390fdbb0e20cddcd372dCAS |
Nelson RM (2002) An effective wind speed for models of fire spread. International Journal of Wildland Fire 11, 153–161.
| An effective wind speed for models of fire spread.Crossref | GoogleScholarGoogle Scholar |
Nelson RM, Butler BW, Weise DR (2012) Entrainment regimes and flame characteristics of wildland fires. International Journal of Wildland Fire 21, 127–140.
| Entrainment regimes and flame characteristics of wildland fires.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38XktFWmt7c%3D&md5=c2d858d16f884c60a8a784bf3b93e135CAS |
Pagni PJ, Peterson TG (1973) Flame spread through porous fuels. In ‘Proceedings of the fourteenth symposium (international) on combustion’, 20–25 August 1972, University Park, PA. pp. 1099–1107. (The Combustion Institute: Pittsburgh, PA)
Pimont F, Dupuy J-L, Linn RR (2012) Coupled slope and wind effects on fire spread with influences of fire size: a numerical study using FIRETEC. International Journal of Wildland Fire 21, 828–842.
| Coupled slope and wind effects on fire spread with influences of fire size: a numerical study using FIRETEC.Crossref | GoogleScholarGoogle Scholar |
Vega JA, Fernandes P, Cuiñas P, Fontúrbel MT, Pérez JR, Loureiro C (2006) Fire spread analysis of early summer field experiments in shrubland fuel types of north-western Iberia. In ‘Proceedings of the 5th international conference on forest fire research’, 2006, Luso, Portugal. (Ed. DX Viegas) (CD-ROM) (ADAI: Coimbra, Portugal).
Viegas DX (2004) On the existence of a steady-state regime for slope and wind driven fires. International Journal of Wildland Fire 13, 101–117.
| On the existence of a steady-state regime for slope and wind driven fires.Crossref | GoogleScholarGoogle Scholar |
Weise DR (1993) Modelling wind and slope-induced wildland fire behavior. PhD thesis, University of California, Berkeley, CA.
Weise DR, Biging GS (1996) Effects of wind velocity and slope on flame properties. Canadian Journal of Forest Research 26, 1849–1858.
| Effects of wind velocity and slope on flame properties.Crossref | GoogleScholarGoogle Scholar |
Zhou X, Mahalingham S, Weise D (2005) Modeling of marginal state of fire spread in live chaparral fuel bed. Combustion and Flame 143, 183–198.
| Modeling of marginal state of fire spread in live chaparral fuel bed.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2MXhtFarsr7E&md5=b7afef7b8d1ea4d6dd2f2950d1fd830dCAS |
