Negative lift characteristics of NACA 0012 aerofoil at low Reynolds numbers

Pranesh, C; Sivapragasam, M; Deshpande, M. D.; Narahari, H. K.

doi:10.1007/s12046-018-1008-6

Cited by 11 publications

(6 citation statements)

References 11 publications

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“…In this section, we present detailed results of the aerodynamic characteristics of NACA 0008 airfoil in the ultra-low range Re [ [1000, 10000]. In an earlier study [19], we presented elaborate results at Re = 2000 and 6000, and the present data complements our previous work. The pressure distribution on the airfoil at a = 0°and 4°are plotted in figure 5.…”

Section: Aerodynamic Characteristics Of Naca 0008 Airfoilsupporting

confidence: 52%

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Aerodynamic shape optimization of airfoils at ultra-low Reynolds numbers

Ukken

Sivapragasam

2019

Sādhanā

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The flow over NACA 0008 airfoil is studied computationally in the ultra-low Reynolds number regime Re [ [1000, 10000] for various angles of attack a [ [0°, 8°]. The laminar flow separation occurs even at low angles of attack in this Reynolds number regime. The lift curve slope is far reduced from the inviscid thin airfoil theory value of C l,a = 2p. Significant increase in the values of drag coefficient is seen with a decrease in Re. Lift-to-drag ratios are consequently very low. An adjoint-based aerodynamic shape optimization methodology is employed to obtain improved aerodynamic characteristics in the ultra-low Re regime. Three different objective functions are considered, namely, (i) minimization of drag coefficient, C d , (ii) maximization of lift coefficient, C l , and (iii) maximization of lift-to-drag ratio, (C l /C d). Significant improvement in each of the objective functions is obtained.

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Section: Aerodynamic Characteristics Of Naca 0008 Airfoilsupporting

confidence: 52%

“…The computed pressure distribution over the NACA 0008 airfoil at Re = 2000 and a = 2°is compared with the available computations [11,12,19] in figure 4. The agreement is good, indicating a validation of the present computational procedure.…”

Section: Computational Procedures and Validationmentioning

confidence: 99%

Aerodynamic shape optimization of airfoils at ultra-low Reynolds numbers

Ukken

Sivapragasam

2019

Sādhanā

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“…16,18 In summary, so far no negative lift slope can be predicted by all these models or theories. Recently, Pranesh et al 28 found comparable regions of negative lift slope for very low RN in the range from 10 k to 100 k by CFD. As the RN is very much sub-critical, we will not comment on this.…”

Section: Justification Of Kutta-joukovsky Condition From Navier-stomentioning

confidence: 90%

A thick aerodynamic profile with regions of negative lift slope and possible implications on profiles for wind turbine blades

Schaffarczyk

Arakawa

2020

Wind Energy

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In the high pressure wind tunnel (HochDruckkanal Goettingen [HDG]) of Deutsch–Niederländische Windkanäle—German–Dutch Wind Tunnels (DNW) a 47% thick airfoil‐like symmetrical profile was investigated at a high (3 to 12 million) Reynolds number. As an unusual feature, a negative lift slope dcL/dα < 0 close to zero lift has been re‐observed under specific circumstances. We describe the findings and offer some explanations using two‐dimensional (2D) unsteady, transitional computational fluid dynamics. Possible implications for very thick aerodynamic profiles for use on wind turbine blades are discussed.

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“…This phenomenon is not new and is typical at low angles of attack [61]. According to the authors of [62], the shape of the separated region, along with the differential growth of boundary layer displacement thickness on the upper and lower surfaces together, introduces an effective negative camber, resulting in a negative circulation around the aerofoil, thereby generating a negative lift.…”

Section: Lift Coefficient Determinationmentioning

confidence: 99%

Hot-Wire Investigation of Turbulence Topology behind Blades at Different Shape Qualities

et al. 2022

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The scope of this paper is to perform a detailed experimental investigation of the shape error effect on the turbulence evolution behind NACA 64-618 airfoil. This airfoil is 3D-printed with predefined typical shape inaccuracies. A high-precision optical 3D scanner was used to assess the shape and surface quality of the manufactured models. The turbulent flow was studied using hot-wire anemometry. The developed force balance device was provided to measure the aerodynamic characteristics of the airfoil. Experimental studies were carried out for three angles of attack, +10∘, 0∘, −10∘, and different chord-based Reynolds numbers from 5.3×104 to 2.1×105. The obtained results show that the blunt trailing edge and rough surface decline the aerodynamic performance of the blades. In addition, the experimental results revealed a strong sensitivity of the Taylor microscale Reynolds number to the type of shape inaccuracy, especially at Re≈1.7×105. We also discuss the evolution of the Reynolds stress components, the degree of flow anisotropy, and the power spectrum distributions depending on the airfoil inaccuracies.

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Negative lift characteristics of NACA 0012 aerofoil at low Reynolds numbers

Cited by 11 publications

References 11 publications

Aerodynamic shape optimization of airfoils at ultra-low Reynolds numbers

Aerodynamic shape optimization of airfoils at ultra-low Reynolds numbers

A thick aerodynamic profile with regions of negative lift slope and possible implications on profiles for wind turbine blades

Hot-Wire Investigation of Turbulence Topology behind Blades at Different Shape Qualities

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