The effect of sampling rate on interpretation of the temporal characteristics of radiative and convective heating in wildland flames
David Frankman A , Brent W. Webb A , Bret W. Butler B C , Daniel Jimenez B and Michael Harrington BA Brigham Young University, Department of Mechanical Engineering, Provo, UT 84602, USA.
B US Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, 5775 Highway 10 W, Missoula, MT 59808, USA.
C Corresponding author. Email: bwbutler@fs.fed.us
International Journal of Wildland Fire 22(2) 168-173 https://doi.org/10.1071/WF12034
Submitted: 25 February 2012 Accepted: 3 July 2012 Published: 11 September 2012
Abstract
Time-resolved radiative and convective heating measurements were collected on a prescribed burn in coniferous fuels at a sampling frequency of 500 Hz. Evaluation of the data in the time and frequency domain indicate that this sampling rate was sufficient to capture the temporal fluctuations of radiative and convective heating. The convective heating signal contained significantly larger fluctuations in magnitude and frequency than did the radiative heating signal. The data were artificially down-sampled to 100, 50, 10, 5 and 1 Hz to explore the effect of sampling rate on peak heat fluxes, time-averaged heating and integrated heating. Results show that for sampling rates less than 5 Hz the difference between measured and actual peak radiative heating rates can be as great as 24%, and is on the order of 80% for 1-Hz sampling rates. Convective heating showed degradation in the signal for sampling rates less than 100 Hz. Heating rates averaged over a 2-s moving window, as well as integrated radiative and convective heating were insensitive to sampling rate across all ranges explored. The data suggest that peak radiative and convective heating magnitudes cannot be fully temporally resolved for sampling frequencies lower than 20 and 200 Hz.
References
Anderson, HE (1969) Heat transfer and fire spread. USDA Forest Service, Intermountain Forest and Range Experiment Station, Research Paper INT 69, pp. 1–20. (Ogden, UT)Beckwith TG, Buck NL, Marangoni RD (1982) ‘Mechanical Measurements.’ (Addison-Wesley: Reading, MA)
Blackledge JM (2003) ‘Digital Signal Processing: Mathematical and Computational Methods, Software Development, and Applications.’ (Horwood Publishing: Chichester, UK)
Bryant R, Womeldorf C, Johnsson E, Ohlemiller T (2003) Radiative heat flux measurement uncertainty. Fire and Materials 27, 209–222.
| Radiative heat flux measurement uncertainty.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXnvFGrur4%3D&md5=7b10234133dd977c4d99127e29924f88CAS |
Butler BW, Cohen J, Latham DJ, Schuette RD, Sopko P, Shannon KS, Jimenez D, Bradshaw LS (2004) Measurements of radiant emissive power and temperatures in crown fires. Canadian Journal of Forest Research 34, 1577–1587.
| Measurements of radiant emissive power and temperatures in crown fires.Crossref | GoogleScholarGoogle Scholar |
Clark TL, Radke L (1999) Analysis of small-scale convective dynamics in a crown fire using infrared video camera imagery. Journal of Applied Meteorology 38, 1401–1420.
| Analysis of small-scale convective dynamics in a crown fire using infrared video camera imagery.Crossref | GoogleScholarGoogle Scholar |
Frankman D (2009) Radiation and convection heat transfer in wildland fire environments. PhD dissertation, Brigham Young University.
Frankman D, Webb BW, Butler BW, Jimenez D, Forthofer JM, Sopko P, Shannon KS, Hiers JK, Ottmar R (2012) Measurements of convective and radiative heating in wildland fires. International Journal of Wildland Fire.
| Measurements of convective and radiative heating in wildland fires.Crossref | GoogleScholarGoogle Scholar | [Published online early 11 September 2012]
Freeborn PH, Wooster MJ, Hao WM, Ryan CA, Nordgren BL, Baker SP, Ichoku C (2008) Relationships between energy release, fuel mass loss, and trace gas and aerosol emissions during laboratory biomass fires. Journal of Geophysical Research – Atmospheres 113, D01301
| Relationships between energy release, fuel mass loss, and trace gas and aerosol emissions during laboratory biomass fires.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 |
Parent G, Acem Z, Lechene S, Boulet P (2010) Measurement of infrared radiation emitted by the flame of a vegetation fire. International Journal of Thermal Sciences 49, 555–562.
| Measurement of infrared radiation emitted by the flame of a vegetation fire.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXhsFaku7vO&md5=5d48db60705174e09c643c63d34f90d4CAS |
Pitts WM, Murthy AV, de Ris J, Filtz J, Nygard K, Smith D, Wetterlund I (2006) Round robin study of total heat flux gauge calibration at fire laboratories. Fire Safety Journal 41, 459–475.
| Round robin study of total heat flux gauge calibration at fire laboratories.Crossref | GoogleScholarGoogle Scholar |
Sacadura JF (2005) Radiative heat transfer in fire safety science. Journal of Quantitative Spectroscopy & Radiative Transfer 93, 5–24.
| Radiative heat transfer in fire safety science.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2MXpt1eltw%3D%3D&md5=0d233646757486a5a086859dd3f68032CAS |
Scott JH, Burgan RE (2005) Standard fire behavior fuel models: a comprehensive set for use with Rothermel’s Surface Fire Spread Model. USDA Forest Service, Rocky Mountain Research Station, General Technical Report RMRS-GTR-153. (Fort Collins, CO)
Shannon CE (1949) Communication in the presence of noise. Proceedings of the Institute of Radio Engineers 37, 10–21.
| Communication in the presence of noise.Crossref | GoogleScholarGoogle Scholar |
Silvani X, Morandini F (2009) Fire spread experiments in the field: temperature and heat fluxes measurements. Fire Safety Journal 44, 279–285.
| Fire spread experiments in the field: temperature and heat fluxes measurements.Crossref | GoogleScholarGoogle Scholar |
Viskanta R (2008) Overview of some radiative transfer issues in simulation of unwanted fires. International Journal of Thermal Sciences 47, 1563–1570.
| Overview of some radiative transfer issues in simulation of unwanted fires.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1cXhtFOlt7rE&md5=421847c12cff731989060b1b99f20754CAS |
Wooster MJ, Roberts G, Perry GLW, Kaufman YJ (2005) Retrieval of biomass combustion rates and totals from fire radiative power observations: FRP derivation and calibration relationships between biomass consumption and fire radiative energy release. Journal of Geophysical Research 110, D24311
| Retrieval of biomass combustion rates and totals from fire radiative power observations: FRP derivation and calibration relationships between biomass consumption and fire radiative energy release.Crossref | GoogleScholarGoogle Scholar |
