逆向涡对超疏水壁面减阻影响的TRPIV实验研究

发布时间：2018-05-23 15:10

  本文选题：超疏水壁面 + 逆向涡　； 参考：《力学学报》2016年05期

【摘要】：超疏水壁面由于具有减阻和自清洁功能而成为国内外减阻和海洋防污等研究领域的热点之一,而20世纪湍流中相干结构的发现为湍流的控制指出新的方向,尤其近壁区涡结构对摩擦阻力贡献很大.利用高时间分辨率粒子图像测速技术,研究了超疏水壁面(SH)以及亲水壁面(PH)湍流边界层中正负展向涡的空间分布特征,研究逆向涡对超疏水壁面近壁区流动结构的影响和超疏水壁面的减阻机理.首先利用空间多尺度局部平均涡量的概念提取壁湍流发卡涡展向涡头(顺向涡)和逆向涡,实现了准确识别涡心并排除小尺度涡的干扰;然后根据检测到的顺向涡和逆向涡流线分布图,发现逆向涡始终处于正向涡的上游和下方,并且对正向涡的进一步发展起抑制作用;最后对两种壁面边界层中逆向涡数量以及出现概率进行对比,发现具有减阻效果的超疏水壁面边界层中出现更多逆向涡.说明逆向涡可抑制上方顺向涡与壁面的强烈剪切,并使靠近壁面的流体加速,从而产生减阻效果;超疏水壁面中涡结构具有更大的β角,使其更好地阻碍了发卡涡头附近强烈的喷射和扫略;超疏水壁面逆向涡出现概率明显大于亲水壁面.这些结果表明:超疏水壁面表现出的减阻特性(Reδ≈13 500,减阻5.8%)与两板产生逆向涡的差异有关.
[Abstract]:Superhydrophobic wall has become one of the hot research fields in the field of drag reduction and marine antifouling because of its drag reduction and self-cleaning function. The discovery of coherent structures in turbulence in the 20th century points out a new direction for turbulence control. In particular, vortex structures near the wall contribute greatly to friction resistance. Using high time resolution particle image velocimetry technique, the spatial distribution characteristics of positive and negative spanwise vortices in the turbulent boundary layer of superhydrophobic wall (SHV) and hydrophilic wall (PH2) are studied. The effect of reverse vortex on the flow structure near the wall of superhydrophobic wall and the drag reduction mechanism of superhydrophobic wall are studied. Firstly, the concept of multi-scale local average vorticity is used to extract the vortex head (forward vortex) and reverse vortex (backward vortex) from wall turbulence, so that the vortex center can be accurately identified and the interference of small-scale vortex can be eliminated. Then according to the detected distributions of the forward vortex and the reverse vortex line, it is found that the reverse vortex is always in the upstream and the lower part of the forward vortex, and it can inhibit the further development of the forward vortex. Finally, by comparing the number and probability of reverse vortices in the two kinds of wall boundary layer, it is found that there are more reverse vortices in the super-hydrophobic boundary layer with drag reduction effect. The results show that the reverse vortex can restrain the strong shear between the upstream vortex and the wall surface, and accelerate the fluid near the wall, thus the drag reduction effect is produced, and the vortex structure in the superhydrophobic wall has a larger 尾 angle. The results show that the strong jet and sweep near the hairpin vortex head are better hindered and the probability of the reverse vortex on the superhydrophobic wall is obviously higher than that on the hydrophilic wall. These results show that the drag reduction characteristics of the superhydrophobic wall are re 未 鈮，

本文编号：1925276