Drag Reduction Using Riblet Film Applied to Airfoils for Wind Turbines

Sareen, Agrim; Deters, Robert W.; Henry, Steven P.; Selig, Michael S.

doi:10.1115/1.4024982

Cited by 57 publications

(41 citation statements)

References 10 publications

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“…On the upper wing the lower side is split in two pressure levels and the lowest differential pressure is approximately at the maximum chord thickness. figure 4, below, the leading edge disturbance, on the right, and how far behind the trailing edge where laminar flow returns [11]. These match and support the results of pressure distribution in figure 3.…”

Section: Resultssupporting

confidence: 77%

Take-off characteristics for NACA 4612 aerofoil in a twin-wing configuration with optimum angles of attack

Witcher

McAndrew²,

Vishnevskaya³

2018

MATEC Web Conf.

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Abstract. Unmanned Aerial Vehicles are used generally at low levels and speeds. The research reported in this article investigates the possible use of twin-wing designs for higher altitudes with a focus on the possible lift capable for either short runways or high payloads. The wing aerofoil and unique Angles of Attack, AoA, are set 5 o on the upper wing and 10 o on the lower. There is a positive upper wing stagger of 50% of the chord length at height separation of 1 chord. These parameters have been established from previous research and this research investigates how they generate lift at take-off and what lift and drag properties exist. It also determines if these parameters are in-line with those for high altitude flight.

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Section: Resultssupporting

confidence: 77%

Take-off characteristics for NACA 4612 aerofoil in a twin-wing configuration with optimum angles of attack

Witcher

McAndrew²,

Vishnevskaya³

2018

MATEC Web Conf.

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“…It has been shown that the air drag can be reduced by 4-5% by engineering the surface with riblet structure of 62 µm [24]. Similarly, Stenzel et al proposed a paint based on aliphatic polyurethane resins that shows air-drag reduction of 6% [25].…”

Section: Wenzel Equation Is Written Asmentioning

confidence: 99%

Studies of drag on the nanocomposite superhydrophobic surfaces

Brassard¹,

Sarkar²,

Perron³

2015

Applied Surface Science

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Highlights• The nanocomposite thin films of stearic acid (SA)-functionalized ZnO nanoparticles incorporated in epoxy polymer matrix have been achieved.• SA-functionalization of ZnO nanoparticles in the thin films was confirmed by XRD and FTIR.• The measured rms roughness of the thin film is found to be 12 ± 1 µm with the adhesion of 5B on glass.• The wetting property shows that the surface of the film is superhydrophobic with the CA of 156 ± 4° and CAH of 4 ± 2°.• The drag reduction on the surface of superhydrophobic glass sphere is 16% lower than as-received glass sphere. AbstractThe nanocomposite thin films of stearic acid (SA)-functionalized ZnO nanoparticles incorporated in epoxy polymer matrix have been achieved. The X-ray diffraction (XRD) studies show the formation of zinc stearate on ZnO nanoparticles as the confirmation of SA-functionalization of ZnO nanoparticles in the thin films. Morphological analyses reveal the presence of micro-holes with the presence of irregular nanoparticles. The measured root mean square (rms) roughness of the thin film is found to be 12 ± 1 µm with the adhesion of 5B on both glass and aluminum substrates. The wetting property shows that the surface of the film is superhydrophobic with the contact angle of water of 156 ± 4° having contact angle hysteresis (CAH) of 4 ± 2°. The average terminal velocity in the water of the as-received glass spheres and superhydrophobic spheres were found to be 0.66 ± 0.01 m/s and 0.72 ± 0.01 m/s respectively. Consequently, the calculated average coefficients of the surface drag of the as-received glass sphere and superhydrophobic glass sphere were 2.30 ± 0.01 and 1.93 ± 0.03, respectively. Hence, the drag reduction on the surface of superhydrophobic glass sphere is found to be approximately 16% lower than as-received glass sphere.Graphical abstract

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“…Here, N is the total number of variables and each variable is chosen as, for instance, N = 4, x 1 = M ∞ , x 2 = Re ∞ , x 3 = P ∞ , and x 4 = α. a and b are coefficients for calculating the response surface. It should be noted that each variable would be non-dimensionalized prior to making a fitting curve using Equation (10). The cross terms in Equation (10) appear to introduce the curvature of the response surface since the fitting curve for this case would not be linear.…”

Section: Of 18mentioning

confidence: 99%

“…Among a number of boundary layer controlling devices such as suction [2,3], blowing [4], synthetic jets [5], vortex generators [6], and riblets [1,[7][8][9][10][11][12], riblets are one of the methodologies used to reduce aircraft surface drag [1,[7][8][9][10][11][12]. Riblets are a passive means of turbulent flow control by which skin friction drag is reduced, and were first employed at the NASA Langley Research Center back in the 1970s [8,13] in imitation of the skin structure of a shark that swims long distances at high speed.…”

Section: Introductionmentioning

confidence: 99%

“…To date, numerous studies on riblets have been conducted concerning the mechanism [8,9,13,14] and effectiveness [10][11][12]15] of riblets in reducing skin friction drag, and their industrial applications in wind turbine blades [10], railways [7], and aircraft [16]. Some design criteria such as the height, width and skewness of the peak shape, and detailed shape of riblets to optimize the reduction of skin friction drag for a flowfield of interest have been clarified.…”

Section: Introductionmentioning

confidence: 99%

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Interpolation of Turbulent Boundary Layer Profiles Measured in Flight Using Response Surface Methodology

et al. 2018

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Turbulent boundary layer profiles on the aircraft surface were characterized by pitot-rake measurements conducted in flight experiments at high subsonic Mach number ranges. Due to slight variations in atmospheric air conditions or aircraft attitudes, such as angles of attack and absolute flight speeds at different flights even under the same premised flight conditions, the boundary layer profiles measured at different flights can exhibit different shape and velocity values. This concern leads to difficulty in evaluating the efficiency of using some kind of drag-controlling device such as riblets in the flight test, since the evaluation would be conducted by comparing the profiles measured with and without using riblets at different flights. An approach was implemented to interpolate the boundary layer profile for a flight condition of interest based on the response surface method, in order to eliminate the influence of the flight conditional difference. Results showed that the interpolation with the 3rd-degree response surface model with a combination of two independent variables of flight Mach number and total pressure successfully eliminated the influence of the flight conditional difference, and interpolated the boundary layer profiles measured at different flights within an inaccuracy of 4.1% for the flight Mach number range of 0.5 to 0.78.

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Drag Reduction Using Riblet Film Applied to Airfoils for Wind Turbines

Cited by 57 publications

References 10 publications

Take-off characteristics for NACA 4612 aerofoil in a twin-wing configuration with optimum angles of attack

Take-off characteristics for NACA 4612 aerofoil in a twin-wing configuration with optimum angles of attack

Studies of drag on the nanocomposite superhydrophobic surfaces

Interpolation of Turbulent Boundary Layer Profiles Measured in Flight Using Response Surface Methodology

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