The relative influence of circulation and buoyancy on fire whirls (FW), blue whirls (BW), and the transition between these regimes of a whirling flame is investigated using a combination of experimental data and scaling analyses. FWs are whirling, turbulent, cylindrical yellow (sooting) flame structures that form naturally in fires and are here created in laboratory experiments. In contrast, a BW is a laminar, blue flame (non-sooting) with an inverted conical shape. Prior measurements of the circulation and heat-release rate are now combined with additional measurements of the flame geometry, particularly the width and height, to provide characteristic length scales for these flames. Using these, a nondimensional circulation (${\Gamma }_f^{*}$) and heat-release rate (${\dot{Q}}_f^{*}$) were defined and shown to correspond to azimuthal (buoyancy driven) and axial momenta, respectively. The ratio ${ℛ}^{*}={\Gamma }_f^{*}/{\dot{Q}}_f^{*}$, a quantity analogous to the swirl number used to characterize swirling jets, was evaluated for FWs and BWs. For FWs, ${ℛ}^{*}1$, so that the flame is circulation dominated. This is argued to be consistent with vortex breakdown being an important part of the transition of FWs to BWs. This work presents a basis for predicting when a BW will form and remain a stable regime. [Keywords] \emph{blue whirl; fire whirl; scaling; vortex breakdown …

中文翻译：

---

循环和浮力对从火旋风向蓝色旋风过渡的影响

结合实验数据和定标分析，研究了循环和浮力对旋涡（FW），蓝涡（BW）以及这些状态之间的过渡的相对影响。FW是在燃烧中自然形成的旋转，湍流，圆柱形黄色（发汗）火焰结构，在此处是通过实验室实验创建的。相反，BW是层状蓝色火焰（不发火），圆锥形倒置。现在将循环和放热率的先前测量值与火焰几何形状（尤其是宽度和高度）的其他测量值结合起来，以提供这些火焰的特征长度标度。使用这些，无量纲循环（${\Gamma }_F^{*}$）和放热率（${\dot{问}}_F^{*}$定义并显示为分别对应于方位角（浮力驱动）和轴向动量。比例${ℛ}^{*}={\Gamma }_F^{*}/{\dot{问}}_F^{*}$评估了FW和BW的量，该量类似于用于表征旋流喷嘴的旋流数。对于固件，${ℛ}^{*}\mathrm{1个}$，使火焰以循环为主。认为这与涡流破裂是一致的，这是FW向BW过渡的重要部分。这项工作为预测BW何时形成并保持稳定状态提供了基础。[关键字] \ emph {blue whirl; 火旋风 缩放 涡旋破坏……