Analysis of transitional separation bubbles on infinite swept wings

Davis, Robert L.; Carter, J. E.; Reshotko, Eli

doi:10.2514/3.9640

Cited by 50 publications

(3 citation statements)

References 13 publications

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“…Comparison with existing correlations to predict the onset of transition for a separated shear layer indicate a good agreement with all the correlations except for the one proposed by Davis, 56 while the end of transition agrees well with transition length correlations given by Mayle 44 and Hatman and Wang. 54 …”

Section: Discussionsupporting

confidence: 73%

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An experimental investigation of a laminar separation bubble on the leading-edge of a modelled aerofoil for different Reynolds numbers

Samson

Sarkar

2015

Proceedings of the Institution of Mechanical Engineers, Part C:

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This paper describes the dynamics of a laminar separation bubble formed on the semi-circular leading edge of constant thickness aerofoil model. Detailed experimental studies are carried out in a low-speed wind tunnel, where surface pressure and time-averaged velocity in the separated region and as well as in the downstream are presented along with flow field visualisations through PIV for various Reynolds numbers ranging from 25,000 to 75,000 (based on the leading edge diameter). The results illustrate that the separated shear layer is laminar up to 20% of separation length and then the perturbations are amplified in the second half attributing to breakdown and reattachment. The bubble length is highly susceptible to change in Reynolds number and plays an important role in outer layer activities. Further, the transition of a separated shear layer is studied through variation of intermittency factor and comparing with existing correlations available in the literature for attached flow and as well as separated flow. Transition of the separated shear layer occurs through formation of K-H rolls, where the intermittency following spot propagation theory appears valid. The predominant shedding frequency when normalised with respect to the momentum thickness at separation remains almost constant with change in Reynolds number. The relaxation is slow after reattachment and the flow takes about five bubble lengths to approach a canonical layer.

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Section: Discussionsupporting

confidence: 73%

“…To predict the onset of transition based on flow conditions at separation, Mayle,44 Hatman and Wang, 54 Praisner and Clark 55 and Davis et al 56 Figure 19. Variation of Clauser parameter after reattachment.…”

Section: Comparison With Correlationsmentioning

confidence: 99%

An experimental investigation of a laminar separation bubble on the leading-edge of a modelled aerofoil for different Reynolds numbers

Samson

Sarkar

2015

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…12 In the region between the start and end of transition, the intermittency function is determined using the model developed by Dhawan and Narasimha. 13 For cases involving separation bubbles the model developed by Roberts 14 and modi ed by Davis et al, 15 is used. Instantaneoustransitionis assumed using the bubble model.…”

Section: Turbulence and Transition Modelsmentioning

confidence: 99%

Study of Boundary-Layer Development in a Two-Stage Low-Pressure Turbine

Dorney

Ashpis

Halstead

et al. 2000

Journal of Propulsion and Power

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Convergence properties of high‐Reynolds‐number separated flow calculations

Rubin

Himansu

1989

Numerical Methods in Fluids

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The convergence properties of an iterative solution technique for the Reduced Navier-Stokes equations are examined for two-dimensional steady subsonic flow over bump and trough geometries. Techniques for decreasing the sensitivity to the initial pressure approximation, for fine meshes in particular, are investigated. They are shown to improve the robustness of the relaxation process and to decrease the computational work required to obtain a converged solution. A semi-coarsening multigrid technique that has previously been found to be particularly advantageous for high-Reynolds-number (Re) flows with flow separation and with highly stretched surface-normal grids is applied herein to further accelerate convergence. Solutions are obtained for the laminar flow over a trough that is more severe than has been considered to date. Sufficient axial grid refinement in this case leads to a shock-like reattachment and, for sufficiently large Re, to a local 'divergence' of the numerical computations. This 'laminar flow breakdown' appears to be related to an instability associated with high-frequency fine-grid modes that are not resolvable with the present modelling. This behaviour may be indicative of dynamic stall or of incipient transition. The breakdown or instability is shown to be controllable by suitable introduction of transition turbulence models or by laminar flow control, i.e. small amounts of wall suction. This lends further support to the hypothesis that the instability is of a physical rather than numerical character and suggests that full three-dimensional analysis is required to properly capture the flow behaviour. Another inference drawn from this investigation is that there is a need for careful grid refinement studies in high-Re flow computations, since coarser grids may yield oscillation-free solutions that cannot be obtained on finer grids.

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Analysis of transitional separation bubbles on infinite swept wings

Cited by 50 publications

References 13 publications

An experimental investigation of a laminar separation bubble on the leading-edge of a modelled aerofoil for different Reynolds numbers

An experimental investigation of a laminar separation bubble on the leading-edge of a modelled aerofoil for different Reynolds numbers

Study of Boundary-Layer Development in a Two-Stage Low-Pressure Turbine

Convergence properties of high‐Reynolds‐number separated flow calculations

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