Aug 21, 2017 - Figure 1. Drag reduction results of direct numeri- cal simulations (DNS) of turbulent channel flow over idealized liquid infused surfaces as a ...
16 TH E UROPEAN T URBULENCE C ONFERENCE , 21-24 AUGUST, 2017, S TOCKHOLM , S WEDEN
TURBULENT DRAG REDUCTION USING LIQUID-INFUSED SURFACES Matthew K. Fu , Isnardo Arenas, Stefano Leonardi & Marcus Hultmark Princeton University, Princeton, NJ, USA University of Texas at Dallas, Dallas, TX, USA
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Superhydrophobic surfaces [SHS] have been shown to reduce viscous drag in turbulent flows[1, 4, 6, 5]. When submerged, air pockets can become trapped in the hydrophobic, microscope roughness elements, 100 resulting in a heterogeneous surface composed of both air-water and 80 solid-water interfaces. The presence of the air-water interfaces generates a localized slip effects, which, when aggregated across the entire 60 surface, manifests itself as an effective slip length and can be associ40 ated with a significant reduction in skin friction drag when exposed to an external flow. 20 Liquid-Infused Surfaces [LIS] present a promising method of ro0 bust, passive drag reduction. Similar to superhydrophobic surfaces, 50 20 40 30 0 10 LIS are heterogeneous surfaces coatings comprised of functionalized, microscale roughness elements that are infused with a chemically b+ = buντ matched fluid. Where SHS rely on trapped air pockets for their properties, LIS utilize any preferentially wetting liquid lubricant. In addition Figure 1. Drag reduction results of direct numerito several beneficial properties including anti-biofouling [2], anti-icing cal simulations (DNS) of turbulent channel flow over + [3], pressure stable omniphobicity and self cleaning [10], LIS have also idealized liquid infused surfaces as a function of b . been experimentally shown to reduce drag in turbulent flows [8]. The Percent drag reduction from various configurations of mechanism by which LIS reduce drag is directly analogous to SHS, idealized liquid infused grooves () compared to a nowhere the localized slipping effect is instead at a liquid-water interface slip wall. (): Drag reduction results from Park et al. [6] using DNS of turbulent channel flow over streaminstead of an air-water interface. Given that LIS have only recently been considered for drag reduction wise shear-free and no-slip stripes. (−): Prediction lined turbuapplications, there is no available framework to relate surface charac- from [7] for drag reduction of slip surface + lent channel flow. Larger values of b correspond to teristics to any resulting drag reduction. Using data from direct numermore drag reduction. ical simulations of turbulent channel flow over grooved configurations of LIS, we demonstrate significant drag reduction achieved. Furthermore, we observe drag reduction even when the viscosity of the lubricant is equal to or exceeds the viscosity of the outer fluid. We show that the drag reduction results are consistent with the existing drag reduction framework and models [7] established for superhydrophobic surfaces (figure 1). Drag reduction is referenced to a no-slip wall and is correlated with the parameter b+ = buτ ν −1 , where b is the effective slip length of the surface, uτ is the friction velocity and ν is the kinematic viscosity. Under the proper conditions, the slip lengths exhibited by the surfaces in turbulent flow are found to agree well with expressions established for Stokes flow [9]. Synthesis of the slip drag reduction framework with these new slip length models can be used to guide the design of LIS for drag reduction applications and experiments. References [1] Robert J. Daniello, Nicholas E. Waterhouse, and Jonathan P. Rothstein. Drag reduction in turbulent flows over superhydrophobic surfaces. Physics of Fluids, 21(8):085103, 2009. [2] A. K. Epstein, T.-S. Wong, R. A. Belisle, E. M. Boggs, and J. Aizenberg. From the Cover: Liquid-infused structured surfaces with exceptional anti-biofouling performance. Proceedings of the National Academy of Sciences, 109(33):13182–13187, 2012. [3] Philseok Kim, Tak Sing Wong, Jack Alvarenga, Michael J. Kreder, Wilmer E. Adorno-Martinez, and Joanna Aizenberg. Liquid-infused nanostructured surfaces with extreme anti-ice and anti-frost performance. ACS Nano, 6(8):6569–6577, 2012. [4] Hangjian Ling, Siddarth Srinivasan, Kevin Golovin, Gareth H Mckinley, Anish Tuteja, and Joseph Katz. High-resolution velocity measurement in the inner part of turbulent boundary layers over super-hydrophobic surfaces. J. Fluid Mech, 801, 2016. [5] Hyungmin Park, Guangyi Sun, and Chang-Jin Kim. Superhydrophobic turbulent drag reduction as a function of surface grating parameters. Journal of Fluid Mechanics, 747:722–734, 2014. [6] Hyunwook Park, Hyungmin Park, and John Kim. A numerical study of the effects of superhydrophobic surface on skin-friction drag in turbulent channel flow. Physics of Fluids, 25(11), 2013. [7] Amirreza Rastegari and Rayhaneh Akhavan. On the mechanism of turbulent drag reduction with super-hydrophobic surfaces. Journal of Fluid Mechanics, 773:R4, 2015. [8] Brian J. Rosenberg, Tyler Van Buren, Matthew K. Fu, and Alexander J. Smits. Turbulent drag reduction over air- and liquid- impregnated surfaces. Physics of Fluids, 28(1):015103, 2016. [9] Clarissa Schönecker, Tobias Baier, and Steffen Hardt. Influence of the enclosed fluid on the flow over a microstructured surface in the Cassie state. Journal of Fluid Mechanics, 740:168–195, 2 2014. [10] Tak-Sing Wong, Sung Hoon Kang, Sindy K. Y. Tang, Elizabeth J. Smythe, Benjamin D. Hatton, Alison Grinthal, and Joanna Aizenberg. Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity. Nature, 477:443–447, 2011.
