Experimental and Theoretical Analysis of Natural Transition on “Infinite” Swept Wing

Arnal, D.; Casalis, Grégoire; Juillen, J. C.

doi:10.1007/978-3-642-84103-3_28

Cited by 47 publications

(18 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In an experimental and theoretical study, Arnal et al 5 compared various parameters from their experiments with results from calculations. The agreement was good, although only a few experimental data points were shown.…”

Section: Transition Predictionmentioning

confidence: 98%

“…Earlier experiments by Arnal et al, 5 Poll, 6 Bippes and NitschkeKowsky, 7 Miiller and Bippes, 8 Dagenhart et al, 9 and Dagenhart and Saric 10 have shown that both stationary and traveling crossflow vortices are present within the three-dimensional boundary layers of swept-wing flows. These instabilities are spawned from inflections in the mean velocity profile and are prevalent in regions of favorable pressure gradients (i.e., near the leading edge).…”

Section: Introductionmentioning

confidence: 96%

See 1 more Smart Citation

Evolution of stationary crossflow vortices in boundary layers on swept wings

Joslin

1995

AIAA Journal

View full text Add to dashboard Cite

The spatial evolution of crossflow-vortex disturbances in a laminar boundary layer on a swept wing is computed by the direct numerical simulation of the incompressible Navier-Stokes equations. A wall-normal velocity distribution of steady suction and blowing at the wing surface is used to generate a strip of equally spaced and periodic disturbances along the span. Three simulations are conducted to study the effect of initial amplitude on both the disturbance evolution and to provide a database for transition-onset prediction methods. As an example application, a theory for a transition model is compared with the direct numerical simulations data. In each simulation, the vortex disturbances first enter a chordwise region that can be described as linear growth; then, the individual disturbances coalesce downsteam and either superpose linearly or interact nonlinearly with adjacent modes; finally, the crossflow vortices enter a region that contains strong nonlinear interactions sufficient to generate inflectional velocity profiles. As the initial amplitude of the disturbance increases (roughness size increases), the length of the evolution to breakdown decreases. In the example application, the three simulations collapse onto a single curve, which is an intermittency correlation for a transition model.

show abstract

Section: Transition Predictionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 96%

Evolution of stationary crossflow vortices in boundary layers on swept wings

Joslin

1995

AIAA Journal

View full text Add to dashboard Cite

show abstract

“…Basic research conducted throughout the last century (e.g., [2][3][4][5][6][7][8][9][10]) has led to a good knowledge about the physics of these phenomena and provided principle ideas how to control them. By continuous research work, the German Aerospace Center (DLR) has built up the capabilities for transition prediction as well as for design and testing of wings and empennages following the NLF (Natural Laminar Flow) and HLFC (Hybrid Laminar Flow Control) concepts.…”

Section: Review Of Recent Research On Laminar Flow Technology In Europementioning

confidence: 99%

Drag Reduction by Laminar Flow Control

et al. 2018

View full text Add to dashboard Cite

Abstract:The Energy System Transition in Aviation research project of the Aeronautics Research Center Niedersachsen (NFL) searches for potentially game-changing technologies to reduce the carbon footprint of aviation by promoting and enabling new propulsion and drag reduction technologies. The greatest potential for aerodynamic drag reduction is seen in laminar flow control by boundary layer suction. While most of the research so far has been on partial laminarization by application of Natural Laminar Flow (NLF) and Hybrid Laminar Flow Control (HLFC) to wings, complete laminarization of wings, tails and fuselages promises much higher gains. The potential drag reduction and suction requirements, including the necessary compressor power, are calculated on component level using a flow solver with viscid/inviscid coupling and a 3D Reynolds-Averaged Navier-Stokes (RANS) solver. The effect on total aircraft drag is estimated for a state-of-the-art mid-range aircraft configuration using preliminary aircraft design methods, showing that total cruise drag can be halved compared to today's turbulent aircraft.

show abstract

“…from the fuselage-wing junction. Later, it was demonstrated that the SHBL as such can be subcritically unstable (Arnal, Perraud & Séraudie 2009) and that transition along the leading edge may occur independently of the spanwise position along the wing (Gray 1952;Arnal, Coustols & Juillen 1984;Kachanov & Moreau 1995). Obviously, a linear stability analysis of the SHBL cannot explain this subcritical transition.…”

mentioning

confidence: 94%

Secondary instability and subcritical transition of the leading-edge boundary layer

2016

View full text Add to dashboard Cite

The leading-edge boundary layer (LEBL) in the front part of swept airplane wings is prone to three-dimensional subcritical instability, which may lead to bypass transition. The resulting increase of airplane drag and fuel consumption implies a negative environmental impact. In the present paper, we present a temporal biglobal secondary stability analysis (SSA) and direct numerical simulations (DNS) of this flow to investigate a subcritical transition mechanism. The LEBL is modelled by the swept Hiemenz boundary layer (SHBL), with and without wall suction. We introduce a pair of steady, counter-rotating, streamwise vortices next to the attachment line as a generic primary disturbance. This generates a high-speed streak, which evolves slowly in the streamwise direction. The SSA predicts that this flow is unstable to secondary, time-dependent perturbations. We report the upper branch of the secondary neutral curve and describe numerous eigenmodes located inside the shear layers surrounding the primary high-speed streak and the vortices. We find secondary flow instability at Reynolds numbers as low as Re ≈ 175, i.e. far below the linear critical Reynolds number Re crit ≈ 583 of the SHBL. This secondary modal instability is confirmed by our three-dimensional DNS. Furthermore, these simulations show that the modes may grow until nonlinear processes lead to breakdown to turbulent flow for Reynolds numbers above Re tr ≈ 250. The three-dimensional mode shapes, growth rates, and the frequency dependence of the secondary eigenmodes found by SSA and the DNS results are in close agreement with each other. The transition Reynolds number Re tr ≈ 250 at zero suction and its increase with wall suction closely coincide with experimental and numerical results from the literature. We conclude that the secondary instability and the transition scenario presented in this paper may serve as a possible explanation for the well-known subcritical transition observed in the leading-edge boundary layer.

show abstract

Experimental and Theoretical Analysis of Natural Transition on “Infinite” Swept Wing

Cited by 47 publications

References 3 publications

Evolution of stationary crossflow vortices in boundary layers on swept wings

Evolution of stationary crossflow vortices in boundary layers on swept wings

Drag Reduction by Laminar Flow Control

Secondary instability and subcritical transition of the leading-edge boundary layer

Contact Info

Product

Resources

About