Control of flow separation around an airfoil at low Reynolds numbers using periodic surface morphing

Jones, Gareth R.; Santer, Matthew; Debiasi, Marco; Papadakis, George

doi:10.1016/j.jfluidstructs.2017.11.008

Cited by 40 publications

(18 citation statements)

References 50 publications

(72 reference statements)

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“…This behaviour could be due to possible energy transfer to the larger coherant structures by means of the periodic forcing. Similar effects were observed by Jones et al [20,21] where the actuation was found to cause a locked-on phenomenon causing the actuation frequency to dominate the spectra. This reduction could be translated into significant noise level reductions, yet the levels of PSD observed for the current amplitudes/ frequencies seems to be weaker than what is observed in literature.…”

Section: B Harmonically Morphing Tef Resultssupporting

confidence: 82%

“…Lee et al [19] carried out a similar study where a pitching NACA 0015 airfoil with a harmonically deflected flap was experimentally tested; the study showed evidence of a great impact on the CL and CM hysteresis while the leading-edge vortex formation and detachment was found to be unaffected by the flap motion. Jones et al [20,21] investigated both experimentally and numerically the use of periodic surface morphing for flow control purposes where the suction side of an airfoil was periodically morphed at various frequencies. Results showed that the actuation frequency dominated the spectra, causing the large coherent structures to add an extra momentum and effectively reduce the separation region, thereby reducing the drag.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Aerodynamic Analysis of a harmonically Morphing Flap Using a Hybrid Turbulence Model and Dynamic Meshing

Abdessemed

Yao

Bouferrouk

et al. 2018

2018 Applied Aerodynamics Conference

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A numerical study of the NACA 0012 airfoil fitted with a harmonically morphing trailing edge flap (TEF) is performed at an angle of attack of 4º and a Reynolds number Re = 0.62×10 6. The study focuses on high frequency, low amplitude configurations for the morphing flap and their effects on the aerodynamic performance and flow structures in the wake. Dynamic meshing methods implemented in the commercial software Ansys Fluent and driven by an in-house user-defined function (UDF) were used to model the TEF deformation using a modified unsteady parametrization. The Stress Blended Eddy Simulation (SBES) hybrid turbulence model was used for all parametric studies. For a fixed amplitude, a range of morphing frequencies (lower and higher than the natural shedding frequency) was explored. Obtained results show that at certain high frequencies a slight increase in aerodynamic efficiency could be achieved compared with a baseline design. When the morphing frequency was fixed at its shedding value, the range of amplitudes investigated indicated the presence of an optimal morphing amplitude for which up to 3% increased aerodynamic efficiency could be obtained. Some preliminary results for upstroke and downstroke TEF oscillations are briefly presented to illustrate some differences compared with the main morphing strategy adopted in the paper.

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Section: B Harmonically Morphing Tef Resultssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Aerodynamic Analysis of a harmonically Morphing Flap Using a Hybrid Turbulence Model and Dynamic Meshing

Abdessemed

Yao

Bouferrouk

et al. 2018

2018 Applied Aerodynamics Conference

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“…2015; Jones et al. 2018) explained reattachment mechanism as follows. The oscillation amplifies the Kelvin–Helmholtz instability, which leads to the earlier rollup of the vortices and generation of a spanwise large coherent structure (LCS).…”

Section: Discussionmentioning

confidence: 99%

“…With the development of smart materials, surface actuators are becoming practicable as active flow control tools. DeMauro et al (2015) and Jones et al (2018) improved aerodynamic performance by producing a standing-wave oscillation on the suction side of an airfoil. Recently, travelling waves have been created experimentally on flexible structures using multiple piezoelectric actuators (Bani-Hani & Karami 2015).…”

Section: Introductionmentioning

confidence: 99%

Reducing flow separation of an inclined plate via travelling waves

Akbarzadeh

Borazjani

2019

J. Fluid Mech.

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Many aquatic animals propel themselves by generating backward traveling waves over their body, which is thought to reattach the flow when the wave speed ($C=\unicode[STIX]{x1D706}f$, where $\unicode[STIX]{x1D706}$ is wavelength and $f$ is frequency) is larger than the swimming speed ($U$). This has inspired the use of travelling waves, which have recently been generated at low amplitudes using smart materials, to reduce flow separation on an inclined plate. To see if low-amplitude travelling waves (amplitude approximately 0.01 of chord length $L$) can reduce the separation on an inclined plate, large-eddy simulations are performed. The simulations are carried out for Reynolds number ($Re$) 20 000 and an angle of attack of $10^{\circ }$ with different wavelengths and frequencies. The travelling waves at a low reduced frequency ($f^{\ast }=fL/U=6$ and $\unicode[STIX]{x1D706}^{\ast }=\unicode[STIX]{x1D706}/L=0.2$, where $U$ is free-stream velocity) do not affect the flow separation and aerodynamic performance compared to the flat inclined plate. Nevertheless, increasing the wave speed by increasing the reduced frequency to 20 and 30 reduces flow separation. However, increasing the wave speed by increasing the wavelength, in contrast to the common belief, does not monotonically reduce the flow separation. In fact, increasing the wave speed by increasing the wavelength from 0.15 to 0.5 at constant frequency $f^{\ast }=20$ increases the separation, but increasing from 0.5 to 1.0 and 2.0, interestingly, reduces flow separation. These observations indicate that the wave speed is not the only parameter for flow reattachment, but both wavelength and frequency individually impact flow separation by affecting two competing but interconnected mechanisms: the axial momentum, imparted onto the fluid by the undulations, tends to reattach the flow but the lateral velocity tends to detach it. In fact, increasing $f^{\ast }$ and $\unicode[STIX]{x1D706}^{\ast }$ increases both the axial momentum and the lateral velocity, which are competing to attach and detach the flow, respectively.

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“…Meanwhile, the efforts for advancement in aerodynamics has been focusing in shape optimization, where the key criteria are to reduce total drags with significant improvement in lift to drag ratio. Numerous studies have also been conducted by using boundary layer control like plasma actuator [3,4] and surface morphing [5] to delay the flow separation. Apart from that, an innovative design concept in morphing technology has gain much interest through the shape-changing ability for acquiring the best possible aerodynamic shape given the flight condition [6,7].…”

Section: Introductionmentioning

confidence: 99%

Parametric study of varying ribs orientation and sweep angle of un-tapered wing box model

Chan¹,

Harmin²,

Othman³

2018

IJET

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A simple un-tapered wing box model was considered to illustrate an aeroelastic tailoring of varying ribs orientation with respect to a range of sweep angles. This approach allows the bending-torsional modes characteristic to be altered hence offering possibility for improvement in aeroelastic performance without having to compromise its overall weight. Two cases of ribs orientation were considered for a range of sweep angles. The first case was by allowing one individual ribs to be orientated at a time and the second case considering all possible combination of ribs orientation. The finding shows that the torsional modes are greatly influenced by the rib orientation while the bending modes are not significantly affected. Therefore, this enable the frequency gap between the flutter modes to be altered; hence resulting into significant impact to aeroelastic performances. It has been found that for all the considered sweep angles, the varying ribs orientation can lead into an improvement of nearly 80-90% when compared to its corresponding baseline configuration. Therefore, this provides a leverage for an advancement in aeroelastic performance without having to penalize the total weight of the wing structure.

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Control of flow separation around an airfoil at low Reynolds numbers using periodic surface morphing

Cited by 40 publications

References 50 publications

Aerodynamic Analysis of a harmonically Morphing Flap Using a Hybrid Turbulence Model and Dynamic Meshing

Aerodynamic Analysis of a harmonically Morphing Flap Using a Hybrid Turbulence Model and Dynamic Meshing

Reducing flow separation of an inclined plate via travelling waves

Parametric study of varying ribs orientation and sweep angle of un-tapered wing box model

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