Study of Reynolds number effects on the aerodynamics of a moderately thick airfoil using a high-pressure wind tunnel

Brunner, Claudia; Kiefer, Janik; Hansen, Martin Otto Lavér; Hultmark, Marcus

doi:10.1007/s00348-021-03267-8

Cited by 22 publications

(21 citation statements)

References 11 publications

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“…To reduce end effects, the model was equipped with elliptical endplates, as shown in figure 2. As detailed in Brunner et al (2021), the low aspect ratio delays stall to higher angles of attack in this experimental set-up. Furthermore, Angulo & Ansell (2019) found that a decrease in aspect ratio can lead to less severe dynamic stall.…”

Section: Airfoil Modelmentioning

confidence: 82%

“…While the motion profiles in the mean angle series (figure 8 a – d ) incrementally exceed the constant static stall angle at , the motion profile in the Reynolds-number series (figure 8 e – h ) is geometrically constant, but instead the static stall angles increase with Reynolds number () (see Brunner et al. 2021).…”

Section: Significance Of the Static Stall Anglementioning

confidence: 95%

“…2016; Brunner et al. 2021). This can also explain why the two lowest-Reynolds-number test cases do not fall on the otherwise convincing trend in figure 9, as the static stall process is smeared out over a range of angles due to a gradual TE separation.…”

Section: Stall Delaymentioning

confidence: 99%

“…The airfoil surface was untripped to promote free transition of the airfoil boundary layer. A thorough description of the set-up can be found in Brunner et al (2021).…”

Section: Airfoil Modelmentioning

confidence: 99%

“…Since the high Reynolds numbers are achieved by increasing the density, the velocities can be kept low (<4.5 m s −1 for all test cases), enabling tests at very low Mach numbers Ma = U/a ≤ 0.013, where a is the speed of sound. Compressibility effects, which have a considerable impact on the dynamic stall process as elucidated by Carr (1988), can thus be neglected. Furthermore, the low velocity implies that the time scales can be kept relatively large, enabling highly dynamic events to be studied at high Reynolds numbers, something that is extremely challenging in conventional facilities.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic stall at high Reynolds numbers induced by ramp-type pitching motions

et al. 2022

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The transient pressure field around a moderately thick airfoil is studied as it undergoes ramp-type pitching motions at high Reynolds numbers and low Mach numbers. A unique set of laboratory experiments were performed in a high-pressure wind tunnel to investigate dynamic stall at chord Reynolds numbers in the range of $0.5\times 10^6\leq Re _c\leq 5.5\times 10^6$ in the absence of compressibility effects. In addition to variations of mean angle and amplitude, pitching manoeuvres at reduced frequencies in the range of $0.01\leq k\leq 0.40$ were studied by means of surface-pressure measurements. Independently of the parameter variations, all test cases exhibit a nearly identical stall behaviour characterized by a gradual trailing-edge stall, in which the dynamic stall vortex forms approximately at mid-chord. The location of the pitching window with respect to the Reynolds-number-dependent static stall angle is found to define the temporal development of the stall process. The time until stall onset is characterized by a power law, where a small excess of the static stall angle results in a drastically prolonged stall delay. The reduced frequency exhibits a decrease in impact on the stall development in the case of angle-limited pitching manoeuvres. Beyond a critical reduced frequency, both load magnitudes and vortex evolution become reduced frequency independent and instead depend on the geometry of the motion and the convective time scale, respectively. Overall, the characteristics of vortex evolution induced by dynamic stall show remarkable similarities to the framework of optimal vortex formation reported in Gharib et al. (J. Fluid Mech., vol. 360, 1998, pp. 121–140). The data from this study are publicly available at https://doi.org/10.34770/b3vq-sw14.

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Section: Airfoil Modelmentioning

confidence: 82%

Section: Significance Of the Static Stall Anglementioning

confidence: 95%

Section: Stall Delaymentioning

confidence: 99%

“…The airfoil surface was untripped to promote free transition of the airfoil boundary layer. A thorough description of the set-up can be found in Brunner et al (2021).…”

Section: Airfoil Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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