An approach to estimating the range of wild fire firebrands transportation by wind

Abstract

Forest wild fire prevention that is carried out to minimize of wild fires number and possible damage from them, is inconceivable without the development of fire-prevention procedures, which are based on data from wild fire monitoring. One of the areas of wild fires monitoring is the evaluation of forest wild fires spreading ability to transportation of firebrands by the wind. This way observed at crown-type of forest wild fires, which are formed from ground ones by transferring the flame to the trees crowns when the wind reaches a certain speed. A mathematical model has been developed for the firebrands transportation by the wind. Mathematical model adequacy was evaluated by inclusion of transfer coefficient as a ratio of firebrand speed to wind speed. The modeling of the horizontal firebrands transportation (sphere, cylinder and disc) has been carried out. Experimental conditions are firebrands have various sizes, fall off from a height of 5-20 m, at a wind speed of 1-5 m⋅s-1. Spherical and discshaped particles have the best transportation ability. The adequacy of the model of horizontal firebrands transportation has been experimentally proved by conducting our own experiments and analyzing information obtained from the literature on similar studies. The results of the experiments showed that with an increase in the air flow speed up to 10 m⋅s-1, the speed of the burning particle does not exceed the speed of the air flow that stimulates it. Thus, it is shown that within the air flow velocity of 1-10 m⋅s-1, the value of the transfer coefficient does not exceed one.