Laminar flow drag reduction on soft porous media.
Laminar flow drag reduction on soft porous media.
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DOI：
10.1038/s41598-017-17141-3
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发表时间：
2017-12-08
影响因子：
4.6
通讯作者：
Ahmadi G
中科院分区：
文献类型：
--
作者：
Mirbod P;Wu Z;Ahmadi G
虽然研究重点是各种涂层表面的减阻，例如超疏水结构和聚合物刷，但了解层流皮肤摩擦系数的基本物理原理以及由于在多孔表面形成有限速度而导致的相关减阻的见解仍然相对未知。在这里，我们通过开发一个框架来模拟通道中牛顿流体的流动，其中下表面被各种多孔介质取代，从而定量研究了多孔介质上的流动。我们发现，多孔介质的存在引起的流动阻力减小取决于渗透率参数α = L/(MK)1/2和高度比δ = H/L的值，其中L是自由流动区域的一半厚度，H是厚度，K是纤维层的渗透率，M是多孔介质中流体的有效动力粘度μe与其动力粘度μ之比。我们还检查了 α → 0 和 α → ∞ 极限情况下渗透层上流动的速度和剪切应力分布。将模型预测与特定多孔介质的实验数据进行比较，结果吻合良好。
While researches have focused on drag reduction of various coated surfaces such as superhydrophobic structures and polymer brushes, the insights tso understand the fundamental physics of the laminar skin friction coefficient and the related drag reduction due to the formation of finite velocity at porous surfaces is still relatively unknown. Herein, we quantitatively investigated the flow over a porous medium by developing a framework to model flow of a Newtonian fluid in a channel where the lower surface was replaced by various porous media. We showed that the flow drag reduction induced by the presence of the porous media depends on the values of the permeability parameter α = L/(MK)1/2 and the height ratio δ = H/L, where L is the half thickness of the free flow region, H is the thickness and K is the permeability of the fiber layer, and M is the ratio of the fluid effective dynamic viscosity μe in porous media to its dynamic viscosity μ. We also examined the velocity and shear stress profiles for flow over the permeable layer for the limiting cases of α → 0 and α → ∞. The model predictions were compared with the experimental data for specific porous media and good agreement was found.
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