Experimental study on attachment length and radiant characteristics of sidewall flame under coupled crosswind velocity and direction angle

Uncontrollable fires in energy storage and transportation systems pose a significant threat to societal sustainability. To enhance fire safety and promote energy management and utilization, this study investigated the evolution of attachment length and radiant characteristics of the sidewall flame under the coupled effects of crosswind velocity and direction angle. The experimental results show that the flame attachment length increases monotonically with heat release rate and crosswind velocity, but first increases and then decreases with crosswind direction angle. Radiant fraction rises with heat release rate, shows a first increase then decrease trend with crosswind velocity, and fluctuates with crosswind direction angle. The distribution of downstream radiative heat flux exhibits three evolutionary patterns: monotonically decreasing, increasing-decreasing and monotonically increasing. This primarily depends on whether the measurement point is covered by the flame. Within the flame-covered region, the radiative heat flux increases with increasing downstream distance. Conversely, for radiometers exposed to the air, the radiative heat flux decreases. Two critical thresholds were proposed to determine the experimental conditions under which the distribution pattern of radiative heat flux occurs. Further analysis reveals that the distance from the fire source to the peak radiative heat flux position has a linear relationship with the flame attachment length. Based on this, a dimensionless prediction model for radiative heat flux was proposed, with the flame attachment length as the key parameter. These findings provide guidance for scientifically assessing the fire risks in energy storage areas and optimizing the fire protection design of energy facilities.