Abstract Dust-devil-like fire whirls without an inner core of flame cause considerable damage due to the strong winds during wildfires and urban fires. The purpose of this study is to clarify the effect of the crosswind speed (U) and heat release rate (HRR) on the circulation, size, and velocity of this type of fire whirl. A U of 0.06–0.54 m/s was investigated at HHRs of 0.84 kW and 2.23 kW. The particle image velocimetry measurements clarified the velocity fields of the vortices and complicated flow structures downwind of a long narrow fire source. The absolute value of the circulation of the vortex increases when the wind speed decreases in the range of 0.28 m/s ≤ U ≤ 0.54 m/s. The radius and velocity of the vortex have the identical tendency. This change in absolute value of the circulation with the crosswind speed is determined by the vortex radius and not by the average vorticity in the vortex. The absolute value of the circulation of the vortex increases when the HRR increases. This relationship is determined by the increase in average vorticity in the vortex and not by the radius of the vortex. This relationship does not depend on the crosswind speed.

中文翻译：

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风速和放热速率对无核心火焰火焰漩涡强度和大小的影响

摘要 在野火和城市火灾期间，由于强风，没有核心火焰的尘魔般的火旋涡会造成相当大的破坏。本研究的目的是阐明侧风速度 (U) 和热释放率 (HRR) 对此类火旋风的循环、大小和速度的影响。在 0.84 kW 和 2.23 kW 的 HHR 下研究了 0.06-0.54 m/s 的 AU。粒子图像测速测量阐明了狭长火源下风处的漩涡和复杂流动结构的速度场。当风速在 0.28 m/s ≤ U ≤ 0.54 m/s 范围内减小时，涡旋环流的绝对值增大。涡流的半径和速度具有相同的趋势。环流绝对值随侧风速度的这种变化是由涡流半径决定的，而不是由涡流中的平均涡度决定的。当 HRR 增加时，涡流环流的绝对值增加。这种关系是由涡流中平均涡量的增加决定的，而不是由涡流半径决定的。这种关系不取决于侧风速度。