论文标题
用微根型各向异性超疏水壁的通道流量的线性稳定性
Linear stability of channel flow with microgroove-type anisotropic superhydrophobic walls
论文作者
论文摘要
我们研究了经受紧张的滑动边界条件的通道流动的时间线性不稳定性，该条件模拟了由微瘤型超超吞噬表面引起的滑动效应。小菜射植物不一定与驱动压力梯度对齐。 Pralits等。物理。流体2，013901（2017）研究了同样的问题，并报告说，在驾驶压力梯度上的微层面的适当倾斜角可以减少关键的雷诺数，并且单个超嗜熟壁的流量比两个超级氢化物壁更不稳定/更稳定。相比之下，我们表明，最低的临界雷诺数总是用两个超疏水壁实现，并且我们获得的临界雷诺数明显低于所报道的。此外，我们表明，可以通过增加滑动长度的各向异性来进一步降低临界雷诺数。随着倾斜角的变化，不稳定性的强度与倾斜角度产生的基本流量的跨流量分量的大小之间似乎存在很强的相关性。如果微层面的倾斜角在两个壁上有所不同，则随着倾斜角的差异的增加，临界雷诺数会增加，即，两个具有平行微胶根的超疏水壁给出了最低的临界雷诺数。结果对于设计微根型壁纹理而言是有益的，以在低雷诺数通道流动下引入不稳定性，这可能是在无法触发湍流的小流量系统中增强混合或热传递的感兴趣。
We study the temporal linear instability of channel flow subject to a tensorial slip boundary condition that models the slip effect induced by microgroove-type super-hydrophobic surfaces. The microgrooves are not necessarily aligned with the driving pressure gradient. Pralits et al. Phys. Rev. Fluids 2, 013901 (2017) investigated the same problem and reported that a proper tilt angle of the microgrooves about the driving pressure gradient can reduce the critical Reynolds number and that the flow with a single superhydrophobic wall is much more unstable/less stable than that with two superhydrophobic walls. In contrast, we show that the lowest critical Reynolds number is always realized with two superhydrophobic walls, and we obtain critical Reynolds numbers significantly lower than the reported. Besides, we show that the critical Reynolds number can be further reduced by increasing the anisotropy in the slip length. As the tilt angle changes, there appears to be a strong correlation between the strength of the instability and the magnitude of the cross-flow component of the base flow incurred by the tilt angle. In case the tilt angles of the microgrooves differ on the two walls, the critical Reynolds number increases as the difference in the tilt angles increases, i.e. two superhydrophobic walls with parallel microgrooves give the lowest critical Reynolds number. The results are informative for designing the microgroove-type wall texture to introduce instability at low Reynolds number channel flow, which may be of interest for enhancing mixing or heat transfer in small flow systems where turbulence cannot be triggered.
