Effect of riblets on turbulence in the wake of an airfoil

Caram, Jose M.; Ahmed, Anwar

doi:10.2514/3.10802

Cited by 27 publications

(10 citation statements)

References 2 publications

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“…Previous research on rectangular, sinusoidal and continuous sawtooth riblets using CFD tools proved that drag can be reduced between the range 8.89% and 24.6% at various AOA (Caram and Ahmed, 1991; Zhang et al , 2011). Based on the analysis in this research work, it is proven that when the raw riblets are used, viscous drag could be reduced between the range 3.17% and 33.08%, and total drag can be reduced up to 3.68% at 30° AOA.…”

Section: Discussionmentioning

confidence: 99%

Computational analysis to enhance the compressible flow over an aerofoil surface

Marimuthu

Chinnathambi²

2021

AEAT

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Purpose Since the inception of aerospace engineering, reducing drag is of eternal importance. Over the years, researchers have been trying to improve the aerodynamics of National Advisory Committee for Aeronautics (NACA) aerofoils in many ways. It is proved that smooth-surfaced NACA 0012 aerofoil produces more drag in compressible flow. Recent research on shark-skin pattern warrants a feasible solution to many fluid-engineering problems. Several attempts were made by many researchers to implement the idea of shark skin in the form of coatings, texture and more. However, those ideas are at greater risk when it comes to wing maintenance. The purpose of this paper is to implement a relatively larger biomimetic pattern which would make way for easy maintenance of patterned wings with improved performance. Design/methodology/approach In this paper, two biomimetic aerofoils are designed by optimizing the surface pattern of shark skin and are tested at different angles of attack in the computational flow domain. Findings The results of the biomimetic aerofoils prove that viscous and total drag can be reduced up to 33.08% and 3.68%, respectively, at high subsonic speed when validated against a NACA 0012 aerofoil. With the ample effectiveness of patched shark-skin pattern, biomimetic aerofoil generates as high as 10.42% lift than NACA 0012. Originality/value In this study, a feasible shark-skin pattern is constructed for NACA 0012 in a transonic flow regime. Computational results achieved using the theoretical model agree with experimental data.

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Section: Discussionmentioning

confidence: 99%

Computational analysis to enhance the compressible flow over an aerofoil surface

Marimuthu

Chinnathambi²

2021

AEAT

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“…Properties of biological materials and surface structures are resulted from a complicated networking between surface architecture and physical and chemical properties (Bhushan 2009(Bhushan , 2016. Surface microstructures play an important role in modern technology specifically in aviation and marine industries to reduce drag force and fuel consumption (Caram and Ahmed 1991;Jimenez 1994;Sundaram et al 1996;Bechert and Hage 2006;Bhushan 2009;Fu et al 2017;Ibrahim et al 2018;Catalano et al 2020) and in wind engineering field (Leitl et al 2020a,b). Geometry of these microstructures is inspired by nature, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Studies conducted by Walsh (1983), Caram and Ahmed (1991), Bechert et al (1997), Dean and Bhushan (2010), Bixler and Bhushan (2013), Martin and Bhushan (2016b) and Husen et al (2020) on a flat plate and various airfoil shapes at different Reynolds numbers have shown a drag reduction benefit up to 10% using shark-skin inspired riblets.…”

Section: Introductionmentioning

confidence: 99%

Bio-inspired Surface Texture Fluid Drag Reduction using Large Eddy Simulation

2023

JAFM

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Skin friction drag can be reduced through the application of bio-inspired riblet surfaces. Numerical simulations were performed using Large Eddy Simulation (LES) to investigate the effect of using riblets on reducing skin friction drag. In this study, three different riblet configurations were used; scalloped, sawtooth and a new design, hybrid, riblet. To validate the effect of using the proposed hybrid riblet design compared with other riblets used in the literature; before applying to complex geometries, they were initially applied to a flat plate in parallel arrangement. Results showed skin friction coefficient reduction of 14% using the proposed hybrid riblet. This reduction was 9.2 times and 1.2 times more compared to sawtooth and scalloped configurations, respectively. The hybrid riblet was then applied partially and fully to NACA 0012 airfoil. Skin friction coefficient reduction of 34.5% was obtained when the hybrid riblet fully applied on the airfoil surface. Furthermore, the Convergent-Divergent (C-D) arrangement was studied, where the riblets were placed fully on the NACA 0012 and aligned with a yaw angle with respect to the flow direction. The convergent lines are inspired by the sensory part of the shark skin, whereas the divergent lines or herringbone are found on the bird feather. The two different riblet configurations, sawtooth and hybrid were modeled with the C-D arrangement and the hybrid riblet with C-D arrangement contributed to higher skin friction coefficient reduction, 34.5%, than the sawtooth riblet shape, 26.75%. Moreover, the C-D arrangement was compared to the parallel arrangement and shown that the C-D arrangement increased the lift coefficient (cl) of the airfoil, the flow separation was delayed and the overall performance of the airfoil was enhanced.

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“…Therefore, researchers have begun to investigate how riblets affect the fluid and aerodynamic performance of airfoil. A widely tested airfoil with riblets is the standard airfoil designed by the National Advisory Committee for Aeronautics (NACA) called NACA0012 [17]. Han [18], tested riblets on the NACA0012 at a Reynolds number of 36,000 and observed a drag reduction of 16%.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Effect of Sawtooth Riblets on Low-Reynolds-Number Airfoil Flow Characteristic and Aerodynamic Performance

et al. 2021

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Riblets with an appropriate size can effectively restrain turbulent boundary layer thickness and reduce viscous drag, but the effects of riblets strongly depend on the appearance of the fabric that is to be applied and its operating conditions. In this study, in order to improve the aerodynamic performance of a low-pressure fan by using riblet technology, sawtooth riblets on NACA4412 airfoil are examined at the low Reynolds number of 1 × 105, and the airfoil is operated at angles of attack (AOAs) ranging from approximately 0° to 12°. The numerical simulation is carried out by employing the SST k–ω turbulence model through the Ansys Fluent, and the effects of the riblets’ length and height on aerodynamic performance and flow characteristics of the airfoil are investigated. The results indicate that the amount of drag reduction varies greatly with riblet length and height and the AOA of airfoil flow. By contrast, the riblets are detrimental to the airfoil in some cases. The most effective riblet length is found to be a length of 0.8 chord, which increases the lift and reduces the drag under whole AOA conditions, and the maximum improvements in both are 17.46% and 15.04%, respectively. The most effective height for the riblet with the length of 0.5 chord is 0.6 mm. This also improves the aerodynamic performance and achieves a change rate of 12.67% and 14.8% in the lift and drag coefficients, respectively. In addition, the riblets facilitate a greater improvement in airfoil at larger AOAs. The flow fields demonstrate that the riblets with a drag reduction effect form “the antifriction-bearing” structure near the airfoil surface and effectively restrain the trailing separation vortex. The ultimate cause of the riblet drag reduction effect is the velocity gradient at the bottom of the boundary layers being increased by the riblets, which results in a decrease in boundary thickness and energy loss.

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Effect of riblets on turbulence in the wake of an airfoil

Cited by 27 publications

References 2 publications

Computational analysis to enhance the compressible flow over an aerofoil surface

Computational analysis to enhance the compressible flow over an aerofoil surface

Bio-inspired Surface Texture Fluid Drag Reduction using Large Eddy Simulation

Numerical Study of Effect of Sawtooth Riblets on Low-Reynolds-Number Airfoil Flow Characteristic and Aerodynamic Performance

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