Laminar flow - The past, present, and prospects

Wagner, R. D.; Bartlett, D. W.; Collier, F. S.

doi:10.2514/6.1989-989

Cited by 17 publications

(6 citation statements)

References 3 publications

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“…Natural Laminar Flow (NLF) technology has been demonstrated to be a powerful tool for drag reduction on aircraft surfaces with zero to moderate sweep angles, where the amplification of streamwise instabilities is the predominant mechanism leading to transitionsee Holmes and Obara (1983), Wagner et al (1989) and Arnal (1992). The drag reduction capability of NLF technology has been verified for a wide range of aircraft classes, from sailplanes to business jets and transport aircraft, as reported in, e.g., Holmes and Obara (1983), Wagner et al (1989) and Hansen (2010). One of the major concerns about the practicability of NLF technology for aircraft drag reduction is related to the achievability of surface smoothness compatible with NLF requirements.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of bump effects on boundary-layer transition in compressible high Reynolds number flow

Costantini¹,

Risius²,

Koch³

et al. 2019

Experimental Thermal and Fluid Science

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The influence of surface bumps on boundary-layer transition was experimentally investigated in the present work. The experiments were conducted in a (quasi-) two-dimensional flow at low to high subsonic Mach numbers and chord Reynolds numbers up to 10 million in the low-turbulence Cryogenic Ludwieg-Tube Göttingen. Various streamwise pressure gradients relevant for natural laminar flow surfaces were examined. Quasi-two-dimensional bumps, with a sinusoidal shape in the streamwise direction, fixed length and three different heights, were installed on a two-dimensional flat-plate model. The model was equipped with temperature-sensitive paint for non-intrusive transition detection and with pressure taps for the measurement of the surface pressure distributions. Boundary-layer transition was shown to occur at a more upstream location with increasing bump height-to-length ratio. This was mainly due to the local adverse pressure gradient on the downstream side of the bump, which was particularly pronounced in the case of the bump with the largest height-to-length ratio, thereby inducing boundary-layer separation (as verified via oil-film visualizations). In the case of the bump with the smallest height-to-length ratio, bumpinduced transition was found to be dependent on global pressure gradient, Mach number and Reynolds number; however, the influence of these parameters on transition induced by bumps with larger height-tolength ratios was significantly reduced. The sensitivity of boundary-layer transition to the effect of the bumps was shown to be more pronounced with stronger global flow acceleration and at smaller Mach numbers.

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Section: Introductionmentioning

confidence: 99%

Experimental study of bump effects on boundary-layer transition in compressible high Reynolds number flow

Costantini¹,

Risius²,

Koch³

et al. 2019

Experimental Thermal and Fluid Science

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“…The dashed curve designated as TF 0 (technology factor of 0) is for natural laminar flow on standard wings [27]. The solid curve, designated as TF 1, refers to natural-laminar-flow airfoils [28].…”

Section: B Aerodynamic Analysis Modulementioning

confidence: 99%

Aerodynamic Considerations in the Design of Truss-Braced-Wing Aircraft

Gur

Schetz

Mason

2011

Journal of Aircraft

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This paper describes a study of the effects of several key aerodynamic considerations on the conceptual design of minimum-fuel/emissions, long-range transport, transonic, truss-braced-wing aircraft configurations. This unconventional configuration has a large benefit over conventional cantilever wing configurations. The truss system enables an increased aspect ratio with lower sweep, thickness ratio, and chords, thus exploiting natural laminar flow. The design problem is solved by a multidisciplinary optimization process, which takes into account both aerodynamic and structural considerations. This paper contains several studies, each of which investigates the dependency of the design space on a specific aerodynamic parameter such as the extent of laminar flow on the wing, cruise Mach number, maximum cruise two-dimensional lift coefficient, supercritical characteristics of the airfoil, winglet influence, and intersection fairing design. In addition, various fuselage drag-reduction technologies are investigated: fuselage relaminarization, surface riblets, tailless arrangements, and Goldschmied propulsion apparatus. All of these studies illustrate the large potential of the truss-braced wing along with additional dragreduction technologies, which may substantially decrease the fuel weight and vehicle emissions.

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“…There has been much activity in laminar flow control approaches over the years with numerous references, 16,17,18,19 and many flight experiments. 20,21 Although much progress has been made to apply laminar flow on wings engine nacelles (B787 has NLF on the engine nacelles 22 ) and tails (B787-9, a stretched version will have hybrid LFC on the horizontal and vertical tails 23 ) significant questions as to optimized design and integration processes, streamlined manufacturing approaches, and long term operational viability have delayed adoption to the subsonic transport fleet.…”

Section: A Technologies Targeted At Viscous Drag Reductionmentioning

confidence: 99%

Fuel Efficiencies Through Airframe Improvements

Bezos‐O'Connor

Mangelsdorf

Nickol

et al. 2011

3rd AIAA Atmospheric Space Environments Conference

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The factors of continuing strong growth in air traffic volume, the vital role of the air transport system on the economy, and concerns about the environmental impact of aviation have added focus to the National Aeronautics Research Policy. To address these concerns in the context of the National Policy, NASA has set aggressive goals in noise reduction, emissions, and energy consumption. With respect to the goal of reducing energy consumption in the fleet, the development of promising airframe technologies is required to realize the significant improvements that are desired. Furthermore, the combination of advances in materials and structures with aerodynamic technologies may lead to a paradigm shift in terms of potential configurations for the future. Some of these promising airframe technologies targeted at improved efficiency are highlighted.

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Laminar flow - The past, present, and prospects

Cited by 17 publications

References 3 publications

Experimental study of bump effects on boundary-layer transition in compressible high Reynolds number flow

Experimental study of bump effects on boundary-layer transition in compressible high Reynolds number flow

Aerodynamic Considerations in the Design of Truss-Braced-Wing Aircraft

Fuel Efficiencies Through Airframe Improvements

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