The flow separation development analysis in subsonic and transonic flow regime of the laminar airfoil

Placek, Robert; Ruchała, Paweł

doi:10.1016/j.trpro.2018.02.029

Cited by 11 publications

(7 citation statements)

References 3 publications

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“…observed. In contrast to experiments of [18] at significantly higher Reynolds numbers, no permanent shock wave is detected. On the pressure side, upstream-travelling shock waves are generated with frequencies (Strouhal numbers) Table 2 Statistical overview of the aerodynamic coefficients for an xy-plane at z = 0.…”

Section: Grid Studycontrasting

confidence: 92%

“…A DNS for the same airfoil by [17] 19] as well as numerical studies [11] [12] in the course of the TFAST project * (part of EU's Horizon 2020 programme). In experiments at considerably higher Reynolds numbers [18], the onset of transonic buffet was observed at similar angels of attack as the one reported in the present contribution. The simulations also potentially provide baseflows for future local and global stability analysis to link the self-sustaining buffet mechanism to a global instability [20].…”

Section: Nomenclaturesupporting

confidence: 88%

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Direct Numerical Simulations of Transonic Flow Around an Airfoil at Moderate Reynolds Numbers

2019

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In order to reduce friction and wave drag on the wings of more efficient next generation aircraft, it is important to understand laminar-turbulent boundary-layer transition and shockwave interactions. In this contribution, fully-resolved direct numerical simulations of Dassault Aviation's V2C profile at transonic conditions and a Reynolds number of half a million are presented. Kelvin-Helmholtz instabilities appear in the shear layers on the pressure-and suction-sides, followed by a self-sustained laminar-turbulent transition process promoted by the stretching of rib vortices between larger co-rotating structures. Multiple acoustic structures interacting with the boundary layer are also observed, together with upstream-propagating shock waves. Regions of flow separation on the suction side exhibit unsteadiness with Strouhal numbers in the range of St ≈ 0.5 − 0.6. This is distinct from a standing wave oscillation in lift at St = 0.12, which agrees well with transonic buffet frequencies, reported for experiments on the same airfoil at higher Reynolds numbers. The insensitivity of the principal results to the chosen grid resolution and spanwise domain size is carefully established.

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Section: Grid Studycontrasting

confidence: 92%

Section: Nomenclaturesupporting

confidence: 88%

Direct Numerical Simulations of Transonic Flow Around an Airfoil at Moderate Reynolds Numbers

2019

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“…All three types have been observed in simulations and experiments. Experimental studies of the same airfoil at higher Reynolds numbers [18] show type A shock motion. The difference between experiments and the present simulations is almost certainly due to Reynolds-number effects [25].…”

Section: Unsteady Flow Structures At α = 4 •mentioning

confidence: 86%

“…In the present contribution direct numerical simulations (DNS) are performed over wingsections at a moderate Reynolds numbers of Re = 500,000 (based on the chord length c) and a Mach number of M = 0.7 considering Dassault Aviation's V2C profile [16]. In the course of the TFAST project, experimental as well as numerical analysis has been carried out on that profile under buffet conditions [17][18][19][20]. There is great interest on global stability analysis of airfoils under buffet conditions (i.e.…”

Section: Introductionmentioning

confidence: 99%

Modal Analysis of a Laminar-Flow Airfoil under Buffet Conditions at Re = 500,000

Zauner

Sandham

2019

Flow Turbulence Combust

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An airfoil undergoing transonic buffet exhibits a complex combination of unsteady shockwave and boundary-layer phenomena, for which prediction models are deficient. Recent approaches applying computational fluid mechanics methods using turbulence models seem promising, but are still unable to answer some fundamental questions on the detailed buffet mechanism. The present contribution is based on direct numerical simulations of a laminar flow airfoil undergoing transonic buffet at Mach number M = 0.7 and a moderate Reynolds number Re = 500,000. At an angle of attack α = 4 • , a significant change of the boundary layer stability depending on the aerodynamic load of the airfoil is observed. Besides Kelvin Helmholtz instabilities, a global mode, showing the coupled acoustic and flow-separation dynamics, can be identified, in agreement with literature. These modes are also present in a dynamic mode decomposition (DMD) of the unsteady direct numerical solution. Furthermore, DMD picks up the buffet mode at a Strouhal number of St = 0.12 that agrees with experiments. The reconstruction of the flow fluctuations was found to be more complete and robust with the DMD analysis, compared to the global stability analysis of the mean flow. Raising the angle of attack from α = 3 • to α = 4 • leads to an increase in strength of DMD modes corresponding to type C shock motion. An important observation is that, in the present example, transonic buffet is not directly coupled with the shock motion.

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“…Incidence fields, at which preceded visible SW instabilities and the flow separation at SW for baseline model configuration, were signed on yellow colour. The flow separation process of the good quality model was described more detailed in [2].…”

Section: Lift Coefficientmentioning

confidence: 99%

Turbulent Triggers and the Model Quality Influence on Aerodynamic Characteristics of the Laminar Aerofoil in Transonic Flow Regime

Placek

Ruchała

2019

Journal of KONES

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The test with a roughness application on the laminar aerofoil has been conducted in the N-3 trisonic wind tunnel of the Institute of Aviation in Warsaw. The main goal of tests was to investigate the influence of the boundary layer transition triggers on a laminar profile aerodynamic characteristic. For baseline configuration, the natural transition was applied. As a local roughness on the upper model surface, the carborundum strips with different heights were applied. These were positioned on the upper model surface in the front of the shock position occurrence. The Mach number during test was equal Ma = 0.7 and Reynolds number was about 2.85·106. Tests have been conducted for different model incidence in range 0°-7°. Current article refers partially to the previous study, where aerofoil model with lower quality of surface had been tested. Investigation results from previous work indicated that some of transition positions improved an aerodynamic characteristic by reducing the drag coefficient value and decreasing shock wave unsteadiness in the transonic regime. However, current article indicates that beneficial effects in respect to the baseline configuration are also strictly dependent on the model quality and turbulent triggers size. Improved surface quality of the laminar aerofoil model affected on aerodynamic characteristics with and without turbulent triggers. Resultant aerodynamic coefficients of all tested cases i.e. drag, lift and lift to drag ratio were compared.

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The flow separation development analysis in subsonic and transonic flow regime of the laminar airfoil

Cited by 11 publications

References 3 publications

Direct Numerical Simulations of Transonic Flow Around an Airfoil at Moderate Reynolds Numbers

Direct Numerical Simulations of Transonic Flow Around an Airfoil at Moderate Reynolds Numbers

Modal Analysis of a Laminar-Flow Airfoil under Buffet Conditions at Re = 500,000

Turbulent Triggers and the Model Quality Influence on Aerodynamic Characteristics of the Laminar Aerofoil in Transonic Flow Regime

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