本文選題：超疏水壁面 + 逆向渦��； 參考：《力學(xué)學(xué)報(bào)》2016年05期

【摘要】：超疏水壁面由于具有減阻和自清潔功能而成為國(guó)內(nèi)外減阻和海洋防污等研究領(lǐng)域的熱點(diǎn)之一,而20世紀(jì)湍流中相干結(jié)構(gòu)的發(fā)現(xiàn)為湍流的控制指出新的方向,尤其近壁區(qū)渦結(jié)構(gòu)對(duì)摩擦阻力貢獻(xiàn)很大.利用高時(shí)間分辨率粒子圖像測(cè)速技術(shù),研究了超疏水壁面(SH)以及親水壁面(PH)湍流邊界層中正負(fù)展向渦的空間分布特征,研究逆向渦對(duì)超疏水壁面近壁區(qū)流動(dòng)結(jié)構(gòu)的影響和超疏水壁面的減阻機(jī)理.首先利用空間多尺度局部平均渦量的概念提取壁湍流發(fā)卡渦展向渦頭(順向渦)和逆向渦,實(shí)現(xiàn)了準(zhǔn)確識(shí)別渦心并排除小尺度渦的干擾;然后根據(jù)檢測(cè)到的順向渦和逆向渦流線分布圖,發(fā)現(xiàn)逆向渦始終處于正向渦的上游和下方,并且對(duì)正向渦的進(jìn)一步發(fā)展起抑制作用;最后對(duì)兩種壁面邊界層中逆向渦數(shù)量以及出現(xiàn)概率進(jìn)行對(duì)比,發(fā)現(xiàn)具有減阻效果的超疏水壁面邊界層中出現(xiàn)更多逆向渦.說(shuō)明逆向渦可抑制上方順向渦與壁面的強(qiáng)烈剪切,并使靠近壁面的流體加速,從而產(chǎn)生減阻效果;超疏水壁面中渦結(jié)構(gòu)具有更大的β角,使其更好地阻礙了發(fā)卡渦頭附近強(qiáng)烈的噴射和掃略;超疏水壁面逆向渦出現(xiàn)概率明顯大于親水壁面.這些結(jié)果表明:超疏水壁面表現(xiàn)出的減阻特性(Reδ≈13 500,減阻5.8%)與兩板產(chǎn)生逆向渦的差異有關(guān).
[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，

本文編號(hào)：1925276