Effect of 3D stall-cells on the pressure distribution of a laminar NACA64-418 wing

Ragni, Daniele; Ferreira, Carlos

doi:10.1007/s00348-016-2215-8

Cited by 21 publications

(10 citation statements)

References 32 publications

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“…The lift increases linearly in the range À7°to 17°and then it curves, maximizing at 17°beyond which c L drops. A similar behavior has been recorded in a recent work by Ragni and Ferreira (2016) for a rectangular wing of the same airfoil and a 4.8 aspect ratio.…”

Section: Steady Casesupporting

confidence: 87%

Experimental study of a pitching and plunging wing

Gkiolas

Yiasemides

Mathioulakis

2018

AEAT

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Purpose The complex flow behavior over an oscillating aerodynamic body, e.g. a helicopter rotor blade, a rotating wind turbine blade or the wing of a maneuvering airplane involves combinations of pitching and plunging motions. As the parameters of the problem (Re, St and phase difference between these two motions) vary, a quasi-steady analysis fails to provide realistic results for the aerodynamic response of the moving body, whereas this study aims to provide reliable experimental data. Design/methodology/approach In the present study, a pitching and plunging mechanism was designed and built in a subsonic closed-circuit wind tunnel as well as a rectangular aluminum wing of a 2:1 aspect-ratio with a NACA64-418 airfoil, used in wind turbine blades. To measure the pressure distribution along the wing chord, a number of fast responding transducers were embedded into the mid span wing surface. Simultaneous pressure measurements were conducted along the wing chord for the Reynolds number of 0.85 × 106 for both steady and unsteady cases (pitching and plunging). A flow visualization technique was used to detect the flow separation line under steady conditions. Findings Elevated pressure fluctuations coincide with the flow separation line having been detected through surface flow visualization and flattened pressure distributions appear downstream of the flow separation line. Closed hysteresis loops of the lift coefficient versus angle of attack were measured for combined pitching and plunging motions. Practical implications The experimental data can be used for improvement of unsteady fluid mechanics problem solvers. Originality/value In the present study, a new installation was built allowing the aerodynamic study of oscillating wings performing pitching and plunging motions with prescribed frequencies and phase lags between the two motions. The experimental data can be used for improvement of computational fluid dynamics codes in case that the examined aerodynamic body is oscillating.

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Section: Steady Casesupporting

confidence: 87%

Experimental study of a pitching and plunging wing

Gkiolas

Yiasemides

Mathioulakis

2018

AEAT

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“…Their statement was supported by the experimental work of Elimelech et al [12] and Dell'Orso et al [13]. Recent experiments conducted by Ragni and Ferreira [14] observed the formation process of stall cells and that once they were generated, they remained stationary.…”

Section: Influential Factors Of Stall Cell Formationmentioning

confidence: 82%

Numerical analysis on the oscillation of stall cells over a NACA 0012 aerofoil

Liu

Nishino

2018

Computers & Fluids

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A series of three-dimensional unsteady Reynolds-averaged Navier-Stokes (RANS) simulations are conducted to investigate the formation and oscillation of stall cells over a NACA 0012 aerofoil. The simulations are conducted with various physical and numerical conditions, such as the Reynolds number, angle of attack, chord-to-span ratio and span-wise mesh resolution. Results show a clear relationship between the oscillation of stall cells and the fluctuation of lift (observed between 17 and 19.5 degrees angle of attack at a high chord Reynolds number of one million). This unsteadiness shows some dependency on the span-wise mesh resolution; it is significant with a medium span-wise mesh resolution (corresponding to 10% of the chord) and moderate with finer resolutions (corresponding to 5% and 2.5% of the chord, respectively). In addition, a proper orthogonal decomposition (POD) method is adopted to further analyse the oscillatory characteristics of stall cells. In particular, it is shown that the first few POD modes have clear spatial patterns corresponding to the profile of stall cells and their time coefficients are correlated with the fluctuation of lift, further confirming the correlation between the stall cell oscillations and the lift fluctuation.

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“…This arrangement prevents flow interference between consecutive pressure taps. 54 Pressure measurements are carried out at a sampling rate of 100 Hz for 10 s. The angle of attack is determined by comparing the measured differential static surface pressure ΔCp = (pss − pps)/(1/2ρU 2 ∞ ) distribution against XFOIL results, 55 shown in Fig. 6(a).…”

Section: Symmetry Of the Setup And Validation Of The Flow Field Measurementsmentioning

confidence: 99%