Unsteady aerodynamics of a wing in a novel small-amplitude transverse gust generator

Fernandez, Fidel; Cleaver, David; Gursul, Ismet

doi:10.1007/s00348-020-03100-8

Cited by 15 publications

(27 citation statements)

References 33 publications

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“…It is likely that the spanwise coherence of the oscillating wakes in these gust generators is far from being two-dimensional in this range. In contrast, the blue triangular symbols, which show the results for a standing-wave type of gust generator (Fernandez, Cleaver & Gursul 2021), reveal very good agreement with the corresponding theoretical solution of Theodorsen (1935). This particular standing-wave gust generator relies on the periodic deflection of the free stream rather than oscillating wakes with travelling waves, and is believed to have better two-dimensionality of the gusts generated.…”

Section: Implications Of Spanwise Coherencesupporting

confidence: 72%

Coherence of unsteady wake of periodically plunging airfoil

2022

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We present an experimental investigation of the flow structure in the near wake of a NACA0012 airfoil plunging sinusoidally at a chord Reynolds number of Re = 20 000 and for a wide range of reduced frequency k and Strouhal number based on peak-to-peak amplitude St. Estimated mean thrust coefficients using the mean and fluctuating velocity fields confirm the St2 dependence as well as a significant effect of the reduced frequency for k ≤ 1. Generally, time-averaged flow quantities are better correlated with St than k in the range tested (k ≤ 3.14 and St ≤ 0.24). Analysis of the streamwise flow and cross-flow in the near wake using two-point cross-correlations and proper orthogonal decomposition reveals that the unsteady characteristics are even better correlated with St than the mean flow quantities. The percentage energy of the fundamental wake modes of the streamwise flow and the flapping mode of the cross-flow increases with increasing St, but at different rates in the drag-producing and thrust-producing wakes. There are similarities to the wake synchronisation behind oscillating bodies. The spanwise-averaged cross-correlation coefficient in the measurement domain grows linearly for small St (in drag-producing wakes), and is nearly constant at a high value for larger St (in thrust-producing wakes). Results show that the Strouhal number is the most important parameter that determines the degree of two-dimensionality of the wake, and suggest that spanwise vortices are quasi-two-dimensional for St ≥ 0.05 and x/c ≤ 4. The implications for experimental gust generators using oscillating airfoils are discussed.

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Section: Implications Of Spanwise Coherencesupporting

confidence: 72%

Coherence of unsteady wake of periodically plunging airfoil

2022

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“…In addition to these, the reduced frequency, which can be considered as a measure of unsteadiness introduced by the oscillating wings, and the maximum deflection angle are of importance in the design of gust generators [8]. Yet, it is discussed that gust response is more sensitive to maximum effective angle of attack than the reduced frequency or the reduced pitch rate [9].…”

Section: Introductionmentioning

confidence: 99%

Design of a gust generator and comparison of model wind turbine and porous disc wake flows in a transverse gust

Yigili

Andirin

Akpolat

et al. 2022

J. Phys.: Conf. Ser.

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This paper outlines the similarities and differences between the wake characteristics of a porous disc and model wind turbine under transverse gust loading which is generated via a two-vane wind tunnel gust generator. Phase-locked two-dimensional two-component (2D2C) particle image velocimetry (PIV) measurements show that the capability of a porous disc in representing a wind turbine increases under gust loading. Compared to the uniform inflow case, normalized streamwise velocity plots of the porous disc and model turbine are in a better agreement under gusty inflow condition particularly in the near wake region. Comparison of the wake centerlines reveals a similar wavy wake pattern with no significant phase lag suggesting that the gust dynamics is the dominant factor in the determination of the wake dynamics.

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“…Gust generators have been widely used to study the unsteady aerodynamic effects of atmospheric flows by modeling natural wind turbulence [1,2]. They constitute important instruments in a wide range of applications that range from the experimental exploration of gusts on uncrewed aerial vehicles (UAV's) [3,4], to gust responses of high aspect ratio wings [5,6], to high speed vehicle environmental effects [7], and atmospheric and building related flows [8,9].…”

Section: Introductionmentioning

confidence: 99%

“…Passive methods introduce a type of obstruction into the inlet flow which causes a steady and repeatable turbulence condition. Active methods rely on controllable moving vanes or tabs to produce larger flow structures and impart turbulent energy into the flow [1,12]. For the work presented here, an active gust generation method was chosen in order to maximize the gust velocity and provide a means of adjusting the gusting frequency.…”

Section: Introductionmentioning

confidence: 99%

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Design, Construction and Evaluation of an Oscillating Vane Gust Generator for Atmospheric Flow Simulation

French

Friess

Goupee

et al. 2021

Wind

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The study of unsteady aerodynamic phenomena in wind tunnels is supported by gust-generating devices capable of generating adjustable magnitude and periodicity velocity fluctuations in a flowfield. Gusts are typically generated actively by introducing moving vanes to direct the flow, or passively by tailoring the boundary layer growth and shape in the tunnel. The flow facility used here is a student-built closed-return low-speed wind tunnel, with a test section size of 750 mm × 750 mm and a maximum speed of 25 m/s. A two-vane gust generator utilizing NACA0018 airfoil sections of 150 mm chord length was designed and installed upstream of the test section. The flowfield was mapped with the installed vanes with and without gust actuation, utilizing a hot wire system. The tunnel with gust vanes exhibits a spatially uniform baseline turbulence intensity of 5%, with a steady state velocity deficit of 1 m/s in the vane–wake region. Upon introducing the gusting conditions at vane deflection angles of up to ±45°, velocity differences of up to 4 m/s were attained at 18 m/s freestream velocity at oscillation frequencies ranging between 1 Hz and 2 Hz.

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Unsteady aerodynamics of a wing in a novel small-amplitude transverse gust generator

Cited by 15 publications

References 33 publications

Coherence of unsteady wake of periodically plunging airfoil

Coherence of unsteady wake of periodically plunging airfoil

Design of a gust generator and comparison of model wind turbine and porous disc wake flows in a transverse gust

Design, Construction and Evaluation of an Oscillating Vane Gust Generator for Atmospheric Flow Simulation

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