The safety during prescribed burnings could be achieved by conducting these operations under marginal conditions of fire propagation. This type of fire can or cannot propagate on account of small deviations of the burning conditions, mainly the wind speed, the fuel load, and the fuel moisture-content. In this context, numerical simulations of grassland fires were conducted under marginal conditions in order to relate the moisture-content threshold of propagation success to the wind speed and the fuel load. The simulations were conducted using FireStar2D, a complete physical 2D fire simulator based on a multiphase modelling approach. The 10 m-open wind speed ranged from 0 to 10 m/s and the fuel load varied from 0.1 kg/m² to 0.7 kg/m². The effects of wind speed and fuel moisture-content on the fire behaviour and on the flame parameters are discussed. The results show that the moisture threshold increases with the fuel load until it reaches a value beyond which there is no dependence. A similar dependence of the moisture threshold on the wind speed is also observed. Finally, empirical formulae were constructed to relate the fuel moisture content threshold to the wind speed and the fuel loading implicitly through Byram's convective number.

规定的燃烧过程中的安全性可以通过在火势蔓延的边缘条件下进行这些操作来实现。由于燃烧条件的微小偏差（主要是风速，燃料负载和燃料水分含量），这种火灾可能会或不会蔓延。在这种情况下，在边际条件下进行了草原火灾的数值模拟，以便将传播成功的水分阈值与风速和燃料负荷相关联。仿真是使用FireStar2D进行的，FireStar2D是基于多相建模方法的完整的物理2D火灾模拟器。10 m的开放风速范围从0到10 m / s，燃料负载从0.1 kg / m ²到0.7 kg / m ²不等。讨论了风速和燃料水分含量对着火行为和火焰参数的影响。结果表明，水分阈值随燃料负荷的增加而增加，直到达到一个没有依赖性的值为止。还观察到湿度阈值对风速的类似依赖性。最后，建立了经验公式，将燃料水分含量阈值与风速和通过Byram对流数隐含的燃料负荷相关联。