Phil's Page

This section reflects the insights gained by Phil Cheney, former senior principal research scientist, CSIRO during forty years of research into all aspects of fire science. Phil was awarded the CSIRO medal for outstanding research achievement in the application of fire science for safer firefighting and safer communities, and the International Association of Wildland Fire Ember Award for Excellence in Wildland fire Science.

Studies of Fire Growth and Convection

A fire has no mass. Therefore, it cannot accelerate but rather it reacts directly to the force driving it – the wind.  As the fire spreads, we say it grows as it gets larger. It produces hot combustion gasses that rise and interact with the wind field above and around all parts of the fire perimeter. This interaction determines the strength and direction of the air movement that impacts the flames at specific parts of the fire perimeter.  In places the wind on the flames will be very different to the strength and direction of the prevailing wind in the open.
As a fire grows its size, shape and speed determines the amount energy released from combustion. About 75% of the total energy is transferred as convective energy and the size and strength of the convection column and its interaction with the windfield around the fire and the resultant wind speed and direction will determine the potential rate of spread for the prevailing conditions, which differ for grassfires and forests. It is critical to understand the growth phase of the fire to ensure the safety of firefighters, including during initial attack.
These topics will be explored in the following sections.
Grass fires 100 seconds after ignition

Fire growth in Grassfires

The factors determining their potential rate of spread.

Initial Attack

Firefighters must make every effort to prevent small fires escaping to threaten people who have absolutely no understanding or experience of bushfires whatsoever.

An image of burnt bush in Australia.
Fire Plume 2003 Alpine Fire

Bushfire convection and the wind field

An insight to the convective structure of both the atmosphere and a bushfire and how they interact.

Prescribed fire for safely securing a wildfire

The first time aerial ignition was used to burn-out a substantial area during summer was on the Myrtleford fire in 1968.

Aerial Flame and Plume
Scroll to Top