Aerodynamic Load Alleviation Using Minitabs

Heathcote, Daniel; Gursul, Ismet; Cleaver, David

doi:10.2514/1.c034574

Cited by 14 publications

(21 citation statements)

References 37 publications

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“…A wire of diameter 0.3 mm was sized using the methods of Pankhurst & Holder [21] and was placed at a chord-wise location, x/c = 0.10. The lift curve (cl -⍺) produced by this set up was previously [1,3] compared to data in literature [22], with similar results obtained for a comparable Reynolds number. The interference and blockage effects were quantified using the methods of Pankhurst & Holder [21], and were determined to have minimal effect [1].…”

Section: Experimental Set-upsupporting

confidence: 80%

“…Placement on the upper surface produces lift decrease: the aim of this study. A comparison [3] of literature for static mini-tab measurements indicates that around the airfoil's zero lift angle the mini-tab's effect on the flow is symmetrically similar for upper and lower surface placement. As such, the effect of periodically deployed mini-tabs on the upper and lower surfaces will be considered concurrently.…”

Section: Periodic Mini-tab Deploymentmentioning

confidence: 93%

“…The mini-tab, a small span-wise strip placed normal to the upper surface of the airfoil, has been proposed as a possible solution. Previous results [2,3] indicate that the mini-tab is effective at reducing lift in a static configuration. The mini-tab separates the flow over a portion of the airfoil surface, providing an effect which is highly dependent on mini-tab height, h/c, chordwise location, xf/c and the airfoil's angle of attack, ⍺.…”

Section: Introductionmentioning

confidence: 92%

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Dynamic Deployment of a Minitab for Aerodynamic Load Control

Heathcote

Gursul

Cleaver

2020

Journal of Aircraft

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Load control is the reduction of extreme aerodynamic forces produced by gusts, maneuvers and turbulence, to enable lighter, more efficient aircraft. To design an effective control system the actuator's response, in terms of amplitude and phase lag, must be known. Current load control technologies are limited to low frequency disturbances due to their large inertia. This paper evaluates a potential high frequency alternative: the mini-tab using periodic and transient deployments on a NACA0012 airfoil in wind tunnel experiments. Periodic deployment for reduced frequencies, k ≤ 0.79 exhibits a normalized lift response amplitude which decays with increasing k comparable to Theodorsen's circulation function, but with substantially higher lag. Transient deployment, at rates as low as τdeploy = U∞tdeploy/c = 1, illustrated a delay in aerodynamic response. The delay is larger for outward mini-tab motion than inward, τ ≈ 6 and 4 respectively for α = 0° and increases with α. The flowfields show that the delay in response and reduction in effectiveness for dynamic mini-tab deployment is due to delayed growth of the separated region behind the mini-tab. The aerodynamic response due to mini-tab deployment was approximated as the response of a first order system, pertinent to control system design. This simple characterization for amplitude reduction and delay in response makes it well suited to loads control.

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Section: Experimental Set-upsupporting

confidence: 80%

Section: Periodic Mini-tab Deploymentmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 92%

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Dynamic Deployment of a Minitab for Aerodynamic Load Control

Heathcote

Gursul

Cleaver

2020

Journal of Aircraft

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“…Microtabs mounted close to the trailing edge become ineffective near stall angles as they get drowned in the separated flow. The load-control effectiveness of microtabs mounted in the fore and mid sections, explored in [131], demonstrate superb load alleviation at both locations, with a slight increment in unsteady forces in the fore section.…”

Section: Microtabsmentioning

confidence: 97%

Review of Flow-Control Devices for Wind-Turbine Performance Enhancement

Akhter

Omar

2021

Energies

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It is projected that, in the following years, the wind‐energy industry will maintain its rapid growth over the last few decades. Such growth in the industry has been accompanied by the desirability and demand for larger wind turbines aimed at harnessing more power. However, the fact that massive turbine blades inherently experience increased fatigue and ultimate loads is no secret, which compromise their structural lifecycle. Accordingly, this demands higher overhaul‐and‐maintenance (O&M) costs, leading to higher cost of energy (COE). Introduction of flow‐control devices on the wind turbine is a plausible solution to this issue. Flow‐control mechanisms feature the ability to effectively enhance/suppress turbulence, advance/delay flow transition, and prevent/promote separation, leading to enhancement in aerodynamic and aeroacoustics performance, load alleviation and fluctuation suppression, and eventually wind turbine power augmentation. These flow‐control devices are operated primarily under two schemes: passive and active control. Development and optimization of flow‐control devices present the potential for reduction in the COE, which is a major challenge against traditional power sources. This review performs a comprehensive and up‐to‐date literature survey of selected flow‐control devices, from their time of development up to the present. It contains a discussion on the current prospects and challenges faced by these devices, along with a comparative analysis centered on their aerodynamic controllability. General considerations and conclusive remarks are presented after the discussion.

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“…Although they tend to be more two-dimensional near the leading-edge, they deform much faster due to the induced velocity field of the tip vortices. Reduced frequencies less than 0.2 are generally more relevant to helicopter rotor blades (McCroskey 1982); however, reduced frequencies up to k ≈ 1 may be important for gust and turbulence response of large civil transport aircraft (Heathcote, Gursul & Cleaver 2018). The relevant reduced frequency range may further increase for manoeuvring aircraft and for small aircraft encountering small-scale gusts.…”

Section: Introductionmentioning

confidence: 99%

Leading-edge vortex dynamics on plunging airfoils and wings

et al. 2022

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The vortex dynamics of leading-edge vortices on plunging high-aspect-ratio (AR = 10) wings and airfoils were investigated by means of volumetric velocity measurements, numerical simulations and stability analysis to understand the deformation of the leading-edge vortex filament and spanwise instabilities. The vortex filaments on both the wing and airfoil exhibit spanwise waves, but with different origins. The presence of a wing-tip causes the leg of the vortex to remain attached to the wing upper surface, while the initial deformation of the filament near the wing tip resembles a helical vortex. The essential features can be modelled as the deformation of an initially L-shaped semi-infinite vortex column. In contrast, the instability of the vortices is well captured by the instability of counter-rotating vortex pairs, which are formed either by the trailing-edge vortices or the secondary vortices rolled-up from the wing surface. The wavelengths observed in the experiments and simulations are in agreement with the stability analysis of counter-rotating vortex pairs of unequal strength.

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Aerodynamic Load Alleviation Using Minitabs

Cited by 14 publications

References 37 publications

Dynamic Deployment of a Minitab for Aerodynamic Load Control

Dynamic Deployment of a Minitab for Aerodynamic Load Control

Review of Flow-Control Devices for Wind-Turbine Performance Enhancement

Leading-edge vortex dynamics on plunging airfoils and wings

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