Vortex development over flat plate riblets in a transitioning boundary layer

Rothenflue, James A.; King, Paul I.

doi:10.2514/3.12579

Cited by 7 publications

(5 citation statements)

References 2 publications

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“…Ehrenstein (1996) considered riblets with a scalloped cross-section and concluded that they always destabilize the flow. Rothenflue & King (1995) observed riblet-induced formation of a streamwise pair of vortices during boundary-layer transition. The same riblets amplify the growth of two-dimensional travelling waves but delay the transformation of Λ-vortices into turbulent spots (Grek, Kozlov & Titarenko 1996).…”

Section: Introductionmentioning

confidence: 91%

Stability of flow in a channel with longitudinal grooves

Moradi

Floryan

2014

J. Fluid Mech.

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The travelling wave instability in a channel with small-amplitude longitudinal grooves of arbitrary shape has been studied. The disturbance velocity field is always three-dimensional with disturbances which connect to the two-dimensional waves in the limit of zero groove amplitude playing the critical role. The presence of grooves destabilizes the flow if the groove wavenumber β is larger than β tran ≈ 4.22, but stabilizes the flow for smaller β. It has been found that β tran does not depend on the groove amplitude. The dependence of the critical Reynolds number on the groove amplitude and wavenumber has been determined. Special attention has been paid to the drag-reducing long-wavelength grooves, including the optimal grooves. It has been demonstrated that such grooves slightly increase the critical Reynolds number, i.e. such grooves do not cause an early breakdown into turbulence.

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Section: Introductionmentioning

confidence: 91%

Stability of flow in a channel with longitudinal grooves

Moradi

Floryan

2014

J. Fluid Mech.

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“…As it can be noticed, the flow topology is very similar to what is observed in Figs. 17 and 18 with the 2 mm plain backward-facing step (3). A second vortex is visible at the footstep in both cases.…”

Section: Resultsmentioning

confidence: 89%

“…On the other hand, the pressure drag variation when considering all the geometries is substantial. For several of them (3,7,9), the pressure component is even stronger than the friction one. Figure 26 presents the global experimental and CFD results obtained in supersonic conditions.…”

Section: Resultsmentioning

confidence: 95%

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Drag Induced by Flat-Plate Imperfections in Compressible Turbulent Flow Regimes

Molton

Hue

Bur

2015

Journal of Aircraft

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This paper presents the results of a coupled experimental and numerical study aimed at evaluating the influence of typical aircraft surface imperfections on the flat-plate drag production in fully turbulent conditions. A test campaign involving high-level measurement techniques, such as microdrag evaluation, near-wall laser Doppler veloeimetry, and oil-film interferometry, has been carried out at several Mach numbers from 0.5 to 1.3 to quantify the impact of a large range of flat-plate imperfections. Forward-facing and backw ard-facing plain and chamfered steps of different heights have been studied. A whole numerical study, based on Reynolds-averaged Navier-Stokes computations, has been completed and used for validation purposes. Given the very small order of magnitude of the forces to be measured and calculated, the relative comparison between experimental and numerical outcomes is satisfactory. Even if some local discrepancies exist, results show an overall good agreement in the positioning of the different imperfection drag productions. Such investigations are of prime interest to determine industrialization tolerances or excrescence geometries offering the best compromises between manufacturing costs and aerodynamic performances.freestream Mach number Palm = atmospheric pressure P, = stagnation pressure Re = freestream Reynolds number T; = stagnation temperature U = velocity U+ = normalized velocity Ur = friction velocity X = longitudinal coordinate z = vertical coordinate Z+ = normalized vertical coordinate < 5 = boundary-layer physical thickness V = kinematic viscosity Subscript O O -freestream state value

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“…Laser velocimetry measurements have shown the principal flow structures resulting from riblets to be a system of longitudinal vortices 44 . The observation that riblets continue to function in the presence of turbulence indicated that the longitudinal vortices could be an effective mechanism for reattachment of separated turbulent LPT flows, which are typically high turbulence environments.…”

Section: Separation Of Low Pressure Turbines At Low Reynolds Numbersmentioning

confidence: 99%

Ultra High Work, High Efficiency Turbines For UAVs

Sondergaard¹

2006

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Vortex development over flat plate riblets in a transitioning boundary layer

Cited by 7 publications

References 2 publications

Stability of flow in a channel with longitudinal grooves

Stability of flow in a channel with longitudinal grooves

Drag Induced by Flat-Plate Imperfections in Compressible Turbulent Flow Regimes

Ultra High Work, High Efficiency Turbines For UAVs

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