Numerical investigation of the effect of wind, slope and fuel moisture on the radiative and convective heating of excelsior fuels

M. S. Sadeghi; Maryam Ghodrat; Duncan Sutherland; Albert Simeoni; Jason Sharples; Harald Kleine

doi:10.1071/WF24115

RESEARCH ARTICLE (Open Access)

Contents Vol 34(4)

Numerical investigation of the effect of wind, slope and fuel moisture on the radiative and convective heating of excelsior fuels

M. S. Sadeghi ^A ^* , Maryam Ghodrat

^A ^* , Duncan Sutherland ^B , Albert Simeoni ^C , Jason Sharples

^B and Harald Kleine ^A

+ Author Affiliations

- Author Affiliations

^A School of Engineering and Technology, University of New South Wales (UNSW), Canberra, Australia.

^B School of Science, UNSW, Canberra, Australia.

^C Department of Fire Protection Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01605, USA.

^* Correspondence to: mohamad.sadeghi@unsw.edu.au, m.ghodrat@unsw.edu.au

International Journal of Wildland Fire 34, WF24115 https://doi.org/10.1071/WF24115

Submitted: 11 July 2024 Accepted: 25 February 2025 Published: 24 March 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of IAWF. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Background

Wind, slope angle and moisture content are the three major parameters that affect fire rate of spread and heat transfer in propagating bushfires.

Aims

This study investigates the effect of the slope angle (0°–40°), wind speed (0–3 m s⁻¹) and fuel moisture content (FMC, 4–12%) on convective heat transfer (cooling and heating) and radiative heat transfer of burning excelsior fuel particles at different locations downstream of a spreading fire.

Methods

The simulations were conducted using Fire Dynamics Simulator (FDS). The zone located downstream of the fire front was divided into two regions: the flame-induced region and the natural convection region.

Key results

For uplifted flames, there is convective cooling of particles downstream of the flame region. However, when the flame attaches to the unburnt fuel, flame depth and fire line intensity both increase, and there is convective heating of the particles ahead of the flames. Radiative heating of the particles also decreases consistently as the distance from the flame increases.

Implications

The results of this analysis reveal the mechanism of local convective and radiative heat transfer to downstream vegetation. Although heat transfer mechanisms are identified from this numerical analysis, these need to be verified through experimental work.

Keywords: convective cooling, convective heating, excelsior, FDS, Fire Dynamics Simulator, flame length, fuel moisture content, Large Eddy Simulation, LES, radiative heat transfer, upslope fire.

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