Airfoil large-eddy breakup devices for turbulent drag reduction

Anders, J. B.; Watson, R. D.

doi:10.2514/6.1985-520

Cited by 26 publications

(8 citation statements)

References 4 publications

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“…1 scaled as indicated in Table 1, Plesniak and Nagib (1985) achieved local skin friction reductions up * A version of this paper was presented at the 12 th Symposium on Turbulence, University of Missouri-Rolla, 24-26 September, 1990 to 35 percent with a net drag reduction of 20 percent, which includes device drag. Anders and Watson (1985) report similar skin friction reductions but with a 7 percent reduction in net drag.…”

Section: Introductionsupporting

confidence: 53%

“…Although no measurements on the device drag were acquired in this investigation, this issue can be examined by looking at previous work. As mentioned in the introduction, Plesniak and Nagib (1985) and Anders and Watson (1985) report net drag reductions but these claims are not based on direct measurements. Sahlin et al (1986 and1988) performed direct drag measurements of a flat plate fitted with LEBU devices in a towing tank.…”

Section: Velocity Profile Datamentioning

confidence: 99%

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Diffusion of slot injected drag-reducing polymer solution in a LEBU modified turbulent boundary layer

Sommer

Petrie

1992

Experiments in Fluids

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The effects of a tandem set of large eddy breakup (LEBU) devices on the diffusion of drag-reducing polymer solution and of water injected into a turbulent boundary layer flow have been studied. Laser Doppler velocimeter measurements were taken in the LEBU modified boundary layer with and without polymer injection. A laser-induced fluorescence technique was used to examine the development of concentration profiles of the injected fluids with increasing distance from the injection slot for a range of injection rates. The diffusion rate of water, a passive contaminant, was diminished by the LEBU devices over a distance of only 10 to 15 boundary layer thicknesses before returning to the case of an unmodified flow; whereas the devices did have a major effect on the diffusion of polymer over the entire streamwise distance studied compared to the case of an unmodified flow. Large reductions of turbulent normal and shear stresses were observed downstream of the devices, especially with polymer injection.

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Section: Introductionsupporting

confidence: 53%

Section: Velocity Profile Datamentioning

confidence: 99%

Diffusion of slot injected drag-reducing polymer solution in a LEBU modified turbulent boundary layer

Sommer

Petrie

1992

Experiments in Fluids

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“…Studies show that turbulence fluctuating velocity is reduced by up to 20% on LEBU device application in comparison to an undisturbed flat plate. LEBU [20][21][22][23] The total net drag reduction, including skin friction C f of the test plate and the LEBU devices, of 10% is reported by Anders [21,22]. Net drag reduction is shown in Figure 10 for the both low and high Reynolds numbers for the thin plate devices.…”

Section: Turbulence Manipulator and Large Eddy Breakup Devicementioning

confidence: 99%

“…The drag reduction for the high Reynolds number (Re c ≈ 7.5×10 4 ) is more than for the low Reynolds number (Re c ≈ 3.1×10 4 ) case Figure 10. NACA 0009 skin friction reduction (right), thin plates net drag reduction (left) [21] throughout the region. Up to a non-dimensionalized distance of 96 boundary layer thicknesses, the net drag reduction is effective for the high Reynolds number.…”

Section: Turbulence Manipulator and Large Eddy Breakup Devicementioning

confidence: 99%

A Conceptual Study of Airfoil Performance Enhancements Using CFD

Ghoddoussi

Miller

2012

AIAA Atmospheric Flight Mechanics Conference

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where the flow reversal normally starts at 86% -chord. A total drag increase of 22% is detected because of the sharp leading-edge of the device, but the main element drag has a reduction of 43%.The maximum lift coefficient does not show a significant change on the same model. The second device (Cylinder) has a negative effect, initiating flow separation and causing a significant decrease in lift-to-drag ratio at a given lift coefficient. The third device (Dimples) demonstrates the potential of lift-to-drag ratio improvement at the higher angle-of-attack. Further investigation is required to verify the results since the improvement is small.

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“…2). The combination of both natural laminar flow over segment^ and turbulent drag-reduction concepts such as riblets 21 and large-eddy-breakup devices 22 over the remainder of the fuselage could reduce viscous fuselage drag by more than 30%. A 30% reduction in fuselage drag of transports has been estimated to lead to an annual savings in fuel cost of as high as 600 million dollars in 1985 for the U.S. civilian transport fleet.…”

Section: Introductionmentioning

confidence: 99%

Effects of compressibility on design of subsonic fuselages for natural laminar flow

Vijgen

Dodbele

Holmes

et al. 1988

Journal of Aircraft

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At high subsonic speeds, density gradients in compressible laminar boundary layers provide increased damping of the two-dimensional and axisymmetric Tollmien-Schlichting instability waves. The favorable influence of flow compressibility provides a unique opportunity to attain natural laminar flow over portions of high-speed subsonic fuselages for drag-reduction purposes. For bodies of moderate fineness ratios (e.g., 5 to 9), the generally destabilizing effect of increasing length-Reynolds number on laminar stability is overpowered by the damping effect of compressibility. Compressible linear stability analyses (based on the e n method) are presented for the laminar boundary layer on axisymmetric body shapes for length-Reynolds numbers up to 86.6 million and Mach numbers up to 0.80. At a fixed Reynolds number, based on body length, it is predicted that the transition-length Reynolds number triples as the Mach number increases from near zero to 0.80. The favorable effects of flow compressibility on laminar stability might be exploited in the design of external fuel tanks, engine nacelles, and fuselages of business or commuter transports. Attainment of natural laminar flow on the forebodies of larger transport fuselages could provide significant reductions in total drag of transport aircraft. NomenclatureA/A 0 = ratio of local disturbance amplitude to amplitude at point of neutral stability for fixed disturbance frequency C D = body drag coefficient (based on frontal area) C Dref = drag coefficient for boundary-layer transition location fixed at x/L = 0.05 at given Mach numberfineness ratio (body length/maximum body diameter) L = body length, ft M = local surface Mach number MO,, = freestream Mach number n = logarithmic exponent of amplitude-growth ratio of unstable Tollmien-Schlichting wave, n = &i(A/A 0 ) R L = Reynolds number based on freestream conditions and body length R TR = Reynolds number based on freestream conditions and transition length T.S. = Tollmien-Schlichting x = axial coordinate starting at nose, ft

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Airfoil large-eddy breakup devices for turbulent drag reduction

Cited by 26 publications

References 4 publications

Diffusion of slot injected drag-reducing polymer solution in a LEBU modified turbulent boundary layer

Diffusion of slot injected drag-reducing polymer solution in a LEBU modified turbulent boundary layer

A Conceptual Study of Airfoil Performance Enhancements Using CFD

Effects of compressibility on design of subsonic fuselages for natural laminar flow

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