An experimental study on the transient runback characteristics of wind-driven film/rivulet flows
An experimental study on the transient runback characteristics of wind-driven film/rivulet flows
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DOI：
10.1063/5.0067672
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发表时间：
2021-11
影响因子：
4.6
通讯作者：
Kai Zhang;Hui Hu
中科院分区：
文献类型：
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作者：
Kai Zhang;Hui Hu
为了更好地了解与飞机结冰现象有关的瞬时地表水输送过程，开展了一项全面的实验活动，以表征风生水film/RiveretflOWS的动态Runback过程。试验研究采用开路风洞产生不同自由流风速的层流边界层空气fl水煤浆，在试验板上驱动薄水film/小河fl水煤浆。利用数字图像投影(DIP)技术实现了film厚度分布的非侵入性、时间和空间分辨率测量，以表征不同试验条件下film/flow的动态Runback过程。基于倾角测量，清楚和定量地揭示了风生水回流过程的重要特征，如在空气/水界面上产生组织良好的二维(即2D)和更复杂的三维(即3D)表面波，film/小溪头部在“加减速”循环中的蹒跚Runback运动，打破前沿接触线形成多条小溪flOw，小溪flOw的曲折和合并。还进行了全面的力平衡分析，以检查相关作用力的变化(即film/riusetflows内部建立的超压力、作用于溪流头部的空气动力阻力以及由于沿液体接触线的表面张力而产生的抑制力)，并评估它们在中断停滞的film/沟渠头部以重新启动风力驱动的film/riusetflows的Runback过程中的重要性。
A comprehensive experimental campaign was conducted to characterize the dynamic runback process of wind-driven water film/rivulet flows for a better understanding of the transient surface water transport process pertinent to aircraft icing phenomena. The experimental study was conducted by using an open-circuit wind tunnel to generate laminar boundary layer airflows with different freestream wind speeds to drive thin water film/rivulet flows over a flat test plate. A digital image projection (DIP) technique was used to achieve non-intrusive, temporally and spatially resolved measurements of the film thickness distributions to characterize the dynamic runback process of the wind-driven film/rivulet flow under different test conditions. Important characteristics of the wind-driven water runback process—such as the generation of well-organized two-dimensional (i.e., 2D) and more complicated three-dimensional (i.e., 3D) surface waves at air/water interfaces, stum-bling runback motion of the film/rivulet heads in “acceleration-and-deceleration” cycles, breaking up the front contact lines to form multiple rivulet flows, meandering and merging of the rivulet flows—were revealed clearly and quantitatively based on the DIP measurements. A comprehensive force balance analysis was also performed to examine the variations of the relevant forces (i.e., the excess pressure forces built inside the film/rivulet flows, aerodynamic drag forces acting on the rivulet heads, and the restraining forces due to the surface tension along the liquid contact lines) and evaluate their importance in the breakoff of the stagnated film/rivulet heads to re-start the runback process of the wind-driven film/rivulet flows