RESEARCH SUMMARY 



This paper presents formulae tables, and figures that can be used to estimate 

 the ratio of mean windspeed acting on the flame from a spreading wildland fire 

 to the mean windspeed 20 ft (6 m) above the vegetation cover. The formulae are 

 based upon the logarithinic windspeed variation law characteristic of constant 

 shear turbulent flow, and are restricted to flat terrain with uniform, continuous 

 vegetation cover. 



By equating integrated bulk drag due to crown foliage to the shear stress at 

 the top of the crown layer, a model for relating windspeed within and below a 

 uniform forest canopy to windspeed 20 ft (6 m) over the canopy is developed. 

 Important variables in this model include stand height, crown closure, foliar 

 surface/ volume ratio, and crown bulk density. Comparison of model predictions 

 with reported experimental measurements shows good agreement. 



