UNS: Robust Superhydrophobic Surfaces for Enhanced Propulsive Performance and Maneuverability at Intermediate Reynolds Number

#1510707 Krueger，Paul S.该提案的目标是通过使用超疏水表面来改善推进力。当水滴滴落在表面上并且水滴与表面之间的角度大于150度时，表面被定义为超疏水的。在这种情况下，可以实现减阻，因为水在超疏水表面上滑动，并且可以在推进中实现节能。 在超疏水表面处使用通过表面的微观纹理捕获在表面附近的气体引入表观滑移可以导致减阻。然而，已知这样的表面具有其自身的挑战，包括在增加的流体静压或动压下气膜的塌陷、通过扩散的气膜的逐渐耗尽以及由微织构特征的间距限制的滑移长度。所提出的努力试图通过对气膜加压来扩展超疏水表面的适用性，这将允许气膜针对压力扰动和扩散的鲁棒稳定。气动稳定具有另外的优点，即改变气膜压力将允许微纹理特征进一步间隔开，增加表观滑移，并且压力的动态变化将允许直接控制表面行为，包括气膜的重新初始化。气动控制表面将使用激光微加工和软光刻技术从聚二甲基硅氧烷构造，并在中间雷诺数（Re）流的扑翼和脉冲喷气推进方法上进行测试。表观滑移引入的超疏水表面上的扑翼和脉冲喷气推进所产生的流场的推进性能的影响将作为Re的函数进行研究。动态致动气膜的能力也将被调查。第二个成果将是提高开发和维持超疏水表面的技术能力，将其应用领域扩大到减阻和自清洁表面的其他情况。提出了通过暑期沉浸进行本科教育的活动，并将开发一个关于机械和生物推进的网上教程，提供给学生和社区。

#1510707Krueger, Paul S.The goal of this proposal is to improve propulsion by using superhydrophobic surfaces. A surface is defined as superhydrophobic when water droplets bead on the surface, and the angle between the drop and the surface is larger than 150 degrees. In cases like this, one can achieve drag reduction, since water slips on the superhydrophobic surface, and energy savings can be realized in propulsion. The introduction of apparent slip at the superhydrophobic surface using gas trapped near the surface by the microtexture of the surface can lead to drag reduction. However, it is known that such surfaces have their own challenges, including collapse of the gas film under increased hydrostatic or dynamic pressure, gradual depletion of the gas film by diffusion, and slip lengths limited by the spacing of the microtexture features. The proposed effort seeks to expand the applicability of superhydrophobic surfaces by pressurizing the gas film, which will allow for robust stabilization of the gas film against pressure disturbances and diffusion. Pneumatic stabilization has the additional advantages that changing the gas film pressure will allow mictotextured features to be spaced further apart, increasing the apparent slip, and dynamic variation of the pressure will allow for direct control of the surface behavior, including re-initialization of the gas film. Pneumatically controlled surfaces will be constructed from polydimethylsiloxane using laser micromachining and soft lithography techniques and tested on flapping-fin and pulsed-jet propulsion methods at intermediate Reynolds number (Re) flows. The effect of apparent slip introduced by the superhydrophobic surfaces on the propulsive performance of flow fields generated by flapping-fin and pulsed-jet propulsion will be investigated as a function of Re. The ability to dynamically actuate the gas film will also be investigated. A secondary outcome would be an improved technical capability in developing and sustaining superhydrophobic surfaces broadening the areas of their application to other cases of drag reduction and self-cleaning surfaces. Activities on undergraduate education through summer immersion were proposed and a web-based tutorial on mechanical and biological propulsion will be developed and made available to students and the community.