The behavior of the disturbance waves is studied in downward adiabatic air-water annular flow in a vertical pipe with an inner diameter of 11.7 mm. The range of liquid wetting densities is 2.5–4.6 cm²/s and the range of superficial gas velocities is 22–57 m/s. The paper is focused on the downstream evolution of the main properties of individual disturbance waves at the stage of flow development along with the process of coalescence of disturbance waves. Brightness-based laser-induced fluorescence technique enabled us to obtain spatiotemporal matrices of the local instantaneous thickness of liquid film along one longitudinal section of the pipe with a length of 400 mm. Dependencies of the main characteristics of the flow on the downstream distance are analyzed. Local shear stress, base film thickness, and longitudinal size of the disturbance waves are stabilized at the distance of 150–200 mm below the inlet. Disturbance wave velocity increases strongly up to this point; further downstream, the acceleration is reduced significantly. Disturbance wave amplitude grows approximately as the square root of distance within the whole region of interrogation. Entrained fraction grows linearly within this region. Disturbance wave frequency decreases exponentially due to the coalescence. It is found that an average disturbance wave surviving through the development stage absorbs two other waves. Individual acts of coalescence of disturbance waves are analyzed quantitatively to investigate their contribution to the change of disturbance wave properties. On average, when a disturbance wave absorbs another one, its speed increases by 2%, its amplitude – by 5–6% and its longitudinal size remains the same. Thus, the disturbance wave properties change downstream mainly due to their individual evolution, not due to coalescence.

在内径为11.7 mm的垂直管中，在绝热的向下空气-水环形流动中研究了扰动波的行为。液体润湿密度范围为2.5–4.6 cm ²/ s，表观气体速度范围为22–57 m / s。本文着眼于流动发展阶段各个扰动波主要特性的下游演变以及扰动波的合并过程。基于亮度的激光诱导荧光技术使我们能够沿长度为400 mm的管道的纵向部分获得液膜局部瞬时厚度的时空矩阵。分析了流动的主要特征对下游距离的依赖性。局部剪切应力，基膜厚度和干扰波的纵向尺寸在入口下方150–200 mm的距离处稳定。到这一点为止，干扰波的速度都会大大增加。在更下游，加速度显着降低。在整个询问区域内，扰动波的振幅大约随着距离的平方根而增加。夹带分数在该区域内线性增长。由于合并，干扰波频率呈指数下降。结果发现，在整个发育阶段幸存下来的平均扰动波会吸收另外两个波。定量分析了干扰波合并的各个行为，以研究它们对干扰波特性变化的贡献。平均而言，当干扰波吸收了另一个干扰波时，其速度会增加2％，其振幅会增加5–6％，并且其纵向大小保持不变。因此，干扰波特性的下游变化主要是由于它们的个体演化，而不是由于聚结。