The Effect of Ground Roughness on Generation and Flow Patterns of Moving Fire Swirl

移动的火灾漩涡是由火区向上的气流与火区周围的风相互作用而产生的。本研究的目的是在室内实验中阐明地面粗糙度对运动火旋流的流型和流场的影响。首先，建立了实验方法，实现水槽实验中出现的移动火旋等现象，即从底部向水槽流动注入稳定的向上流动。用染料将流动模式可视化。流场测量采用电磁风速仪或图像处理。本研究的主要结果如下：1)移动的火灾漩涡只有在火区向上的气流相对于一般风足够强的情况下才会产生。根据雷诺数、一般风速和火区宽度将流型分为固定涡型和收缩涡型。地面粗糙度的作用是削弱一般风的强度。2)在固定涡型中，火区后方会产生较强的上游和向上流，也会产生强烈的湍流。(3)在收缩涡型中，每个涡旋都是随着涡旋声的减小和上升电流的增大而向下运动。

Moving fire swirl is to be generated by interaction of the upward flow from fire region and general wind around the fire region. The purpose of this research is to clarify, in laboratory experiments, the effect of ground roughness on the flow patterns and flow field of the moving fire swirl. At first, experimental method was established to realize those phenomenon like moving fire swirl in the water flume experiment, that is, we injected steady upward flow into the flume flow from the bottom. The flow patterns were visualized with dye. The flow field was measured with electro-magnetic anemometer or image processing. The main result of this research is as follows.1)Moving fire swirl is generated only when the upward flow from the fire region is strong enough compared to the general wind. The flow patterns are divided into the fixed vortex type and shrunk vortex type by the Reynolds number with general wind velocity and fire region width. The effect of the ground roughness is to weaken the strength of the general wind.2)In the Fixed vortex type, strong currents toward upstream and upward are generated behind the fire region, which also generated intense turbulence.3) In the shrunk vortex type, each vortex moves down with decrease its votice and increase of an upward current.