Optimal Microstructures Drag Reducing Mechanism of Riblets

Friedmann, Elfriede; Richter, Thomas

doi:10.1007/s00021-010-0033-y

Cited by 12 publications

(6 citation statements)

References 11 publications

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“…Alternatively, much work has been done on shark-skin inspired surfaces, known as riblets [19,62,[71][72][73][74][75]. These bioinspired surfaces modify the near-wall vorticity during turbulent flow, reducing skin friction in the fully wetted Wenzel state.…”

Section: Discussionmentioning

confidence: 99%

Bioinspired surfaces for turbulent drag reduction

Golovin

Gose

Perlin

et al. 2016

Phil. Trans. R. Soc. A.

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In this review, we discuss how superhydrophobic surfaces (SHSs) can provide friction drag reduction in turbulent flow. Whereas biomimetic SHSs are known to reduce drag in laminar flow, turbulence adds many new challenges. We first provide an overview on designing SHSs, and how these surfaces can cause slip in the laminar regime. We then discuss recent studies evaluating drag on SHSs in turbulent flow, both computationally and experimentally. The effects of streamwise and spanwise slip for canonical, structured surfaces are well characterized by direct numerical simulations, and several experimental studies have validated these results. However, the complex and hierarchical textures of scalable SHSs that can be applied over large areas generate additional complications. Many studies on such surfaces have measured no drag reduction, or even a drag increase in turbulent flow. We discuss how surface wettability, roughness effects and some newly found scaling laws can help explain these varied results. Overall, we discuss how, to effectively reduce drag in turbulent flow, an SHS should have: preferentially streamwise-aligned features to enhance favourable slip, a capillary resistance of the order of megapascals, and a roughness no larger than 0.5, when non-dimensionalized by the viscous length scale.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'.

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Section: Discussionmentioning

confidence: 99%

Bioinspired surfaces for turbulent drag reduction

Golovin

Gose

Perlin

et al. 2016

Phil. Trans. R. Soc. A.

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“…However, in many applications, obstacles may have rough boundaries. This is the case, for instance, for the skin of sharks ( [22,23]) or golf balls. Another application of interest can also be found for instance in aerodynamics in drag control of aircraft wings.…”

Section: Introductionmentioning

confidence: 99%

Weighted Hilbert spaces for the stationary exterior Stokes problem with Navier slip boundary conditions

Dhifaoui

Meslameni

Razafison

2019

Journal of Mathematical Analysis and Applications

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In this paper, we analyse the three-dimensional exterior Stokes problem with the Navier slip boundary conditions, describing the flow of a viscous and incompressible fluid past an obstacle where it is assumed that the fluid may slip at the boundary. Because the flow domain is unbounded, we set the problem in weighted spaces in order to control the behavior at infinity of the solutions. This functional framework also allows to prescribe various behaviors at infinity of the solutions (growth or decay). Existence and uniqueness of solutions are shown in a Hilbert setting which gives the tools for a possible numerical analysis of the problem. Weighted Korn's inequalities are the key point in order to study the variational problem.

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“…A refinement was later done in the context of shape optimization [7], [9] and [8]. We consider the Navier-Stokes equations rescaled to viscous wall units [19] with a Couette profile defined by the no-slip boundary condition on the rough surface and the prescribed velocity on the top which can have an arbitrary direction due to the turbulences in the above regions.…”

Section: Near-wall Models For Drag Calculationmentioning

confidence: 99%

Drag Evaluations on Rough Surfaces From Near-Wall Models

Friedmann¹,

Kim²,

Ri³

2017

Topical Problems of Fluid Mechanics 2017

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In this paper we evaluate the drag of periodic rough microstructures from near-wall models. With near-wall models we denote Coutte flows which describe the viscous boundary layer of turbulent flows. The structures inside this layer are not the optimal ones but can be used for a deeper understanding of the drag reducing mechanism of riblets due to a valid mathematical theory for viscous flows. Here, the numerical calculations can be validated and the developed calculation strategies can later be extended to the turbulent boundary layer. The focus of this paper is the evaluation of the drag of several microstructures for a better understanding of their action to the turbulent overflow. The influence of the structures will be visible trough a shift in the mean velocity profile which will be quantified. Due to the fixed calculation domain and thus an altered sublayer thickness, the obtained drag values can not be easily compared. We will as well present a theory for the comparison of the drag of rough surfaces calculated from our near-wall models as one for the comparison of rough versus smooth surface.

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Optimal Microstructures Drag Reducing Mechanism of Riblets

Cited by 12 publications

References 11 publications

Bioinspired surfaces for turbulent drag reduction

Bioinspired surfaces for turbulent drag reduction

Weighted Hilbert spaces for the stationary exterior Stokes problem with Navier slip boundary conditions

Drag Evaluations on Rough Surfaces From Near-Wall Models

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