Abstract In the present study, an experimental study was conducted to characterize the effects of initial ice roughness on the transient behaviors of surface water/ice run-back over a NACA 23012 airfoil model under a glaze icing condition. The experimental study was conducted in the Icing Research Tunnel of Iowa State University (i.e., ISU-IRT). A digital image projection (DIP) technique was applied to provide non-intrusive, temporally-and-spatially-resolved measurements of the thickness distributions of the dynamic water/ice flows over the airfoil surface. Two typical surface morphologies were observed for the surface water runback over the airfoil models: water film flow and water rivulets flow. While the surface water film flow modulated with one primary wave and multiple secondary waves is observed at lower wind speed conditions (i.e., U∞ = 10 m/s), the water rivulets flow is observed at relatively higher wind speed conditions (i.e., U∞ = 15 m/s). The initial ice roughness is found to retard and shorten the primary wave formation in the water film flow. It is also found that the initial ice roughness could trap and decelerate the water flow and decrease the inertia force in the film front, which essentially delays the formation of the rivulets. The water rivulet flow trapped by the initial roughness was found to have a meandering behavior, due to which, the initially formed narrow rivulets merged into wider rivulets as they move downstream. By recognizing the film/rivulets boundary during the dynamic surface water/ice runback process, the quantitative details were extracted, i.e., the formation, transition, and development of the rivulet flows. The initial ice roughness was found to have a significant effect on the rivulet characteristics (e.g., rivulet width, spacing, and height).

中文翻译：

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表征初始冰粗糙度对机翼表面风驱动水回流影响的实验研究

摘要 在本研究中，进行了一项实验研究，以表征初始冰粗糙度对 NACA 23012 机翼模型在釉面结冰条件下地表水/冰回流瞬态行为的影响。实验研究是在爱荷华州立大学结冰研究隧道（即 ISU-IRT）中进行的。应用数字图像投影 (DIP) 技术来提供对机翼表面上动态水/冰流的厚度分布的非侵入式、时间和空间分辨测量。对于翼型模型上的地表水回流，观察到两种典型的表面形态：水膜流和水流。而在较低风速条件下观察到用一个初级波和多个次级波调制的地表水膜流（即 U∞ = 10 m/s），在相对较高的风速条件下（即 U∞ = 15 m/s）观察到水流。发现初始冰粗糙度会延迟和缩短水膜流中的初级波形成。还发现初始冰粗糙度可以捕获和减速水流并降低薄膜前沿的惯性力，这实质上延迟了小溪的形成。发现被初始粗糙度捕获的水流具有蜿蜒的行为，因此，最初形成的狭窄的小溪在向下游移动时合并为更宽的小溪。通过识别动态地表水/冰回流过程中的膜/溪流边界，提取定量细节，即溪流的形成、转变和发展。