Spray cone angle (θ) and width (H) have been widely used to characterize morphology of jets. However, to a flashing jet, their capabilities are restrained by two flaws: (a) they are variable as a function of axial distance (θ (H)=f(x)), leading to nonunified θ or H at different axial locations, and (b) fail to precisely capture key characteristics of nonlinear boundary of expansion zone, resulting in their disability to determine the flashing jet regimes. In this work, a power function |y|=kx^0.5, in which x and y are axial and radical directions respectively, characterizing the nonlinear boundary of expansion zone of flashing jet is proposed. A variety of experiments are conducted to validate the proposed method. Experimental results demonstrate that the graphical parameter k unifies a cluster of spray angles (θ=f(x))), and furthermore, owns a good capability to characterize morphological dynamics of flashing jet. These merits allow k to determine the flashing jet regimes. In this work, k<1, 1<k<5, and k>5 are the determining criteria for the external, internal transition, and full flashing jet regimes, respectively.

喷雾锥角（θ）和宽度（H）已被广泛用于表征射流的形态。但是，对于闪光射流而言，它们的能力受到两个缺陷的限制：（a）它们是随轴向距离变化的函数（θ（H）= f（x）），导致在不同的轴向位置出现不统一的θ或H， （b）无法精确地捕捉到膨胀带非线性边界的关键特征，从而导致它们无法确定闪烁的射流状态。在这项工作中，幂函数| y | = kx ^0.5，其中x和y分别给出了轴向和径向两个方向的特征，提出了一种表征急流扩张区非线性边界的特征。进行各种实验以验证所提出的方法。实验结果表明，图形参数k统一了一组喷射角（θ = f（x）），此外，它还具有良好的表征喷流形态动力学的能力。这些优点使k可以确定闪烁的喷射方式。在这项工作中，k <1，1 < k <5和k > 5分别是外部，内部过渡和全闪光射流状态的确定标准。