论文标题
润滑层中表面复杂性引起的抗性的预测：应用于超吞噬表面
Prediction of resistance induced by surface complexity in lubricating layers: Application to super-hydrophobic surfaces
论文作者
论文摘要
超疏水（SH）涂层被广泛用于减轻各种应用中的阻力。许多研究表明，这些材料产生的有益壁滑效应在层流方向上消失了。被认为是性能下降的主要机制是Marangoni诱导的应力和空气/液体界面变形。在本研究中，提出了一种新的机制来解释层状流动方案中SH曲面的性能丧失。在这里，我们考虑了lone内的空气流以及相关的动量损失，这些元素具有不同的几何特征的粗糙度元素。与均质边界条件方法相结合的等位基因中的空气运动的影响与外流体耦合。为此，在粗糙度元件的尺度上进行的数值模拟是作为孔隙率和域的曲折度的函数进行的，以确定空气液体界面处的滑动速度。 然后，在外流的理论模型中实现了均质的边界条件，以计算以低$ re $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $的sh-spheres上的阻力。层状SH落球的实验表明，高曲折度和低值的孔隙率值会导致在考虑减少阻力时的性能丧失。如预期的那样，一个具有低曲折和类似孔隙率的3D打印球体显示出近乎最佳的阻力减少。预测值和实验之间的比较研究表明，同质模型能够准确预测SH表面上的阻力，以从SH纹理表面的显微镜图像中估算出的孔隙率和曲折度值。
Super Hydrophobic (SH) coatings are widely used to mitigate drag in various applications. Numerous studies have demonstrated that the beneficial wall-slip effect produced by these materials disappears in laminar flow regimes. The main mechanisms considered to be behind the decrease in performance are Marangoni-induced stresses and air/liquid interface deformation. In the present study, a new mechanism is proposed to explain the loss of performances of SH-surfaces in laminar flow regimes. Here we consider the flow of air inside the plastron and the associated momentum loses induced by roughness elements with different geometric characteristics. The effects of air motion within the plastron is coupled to the outer fluid with a homogenised boundary condition approach. To this end, numerical simulations at the scale of the roughness element were conducted as a function of the porosity and the tortuosity of the domain to determine the slip velocity at the air-liquid interface. The homogenised boundary condition is then implemented in a theoretical model for the outer flow to compute drag on SH-spheres at low $Re$ numbers. Experiments of laminar SH falling spheres indicate that high values of the tortuosity and low values of porosity lead to a loss of performances when considering drag reduction. As anticipated, a 3D printed sphere with low tortuosity and similar porosity demonstrated near-optimal drag reductions. A comparative study between the predicted values and experiments shows that the homogenised model is able to accurately predict the drag on SH surfaces for values of the porosity and tortuosity estimated from microscopy images of the SH textured surface.
