Design optimization of the aerodynamic passive flow control on NACA 4415 airfoil using vortex generators

Fouatih, Omar Madani; Médale, Marc; Imine, Omar; Imine, Bachir

doi:10.1016/j.euromechflu.2015.11.006

Cited by 84 publications

(50 citation statements)

References 19 publications

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“…Notwithstanding, the observed influence of spacing is relatively low compared with other parameters, in agreement with previous observations on CoR and CtR arrays. ()…”

Section: Resultsmentioning

confidence: 99%

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Experimental parameter study for passive vortex generators on a 30% thick airfoil

et al. 2018

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Passive vane–type vortex generators (VGs) are commonly used on wind turbine blades to mitigate the effects of flow separation. However, significant uncertainty surrounds VG design guidelines. Understanding the influence of VG parameters on airfoil performance requires a systematic approach targeting wind energy‐specific airfoils. Thus, the 30%‐thick DU97‐W‐300 airfoil was equipped with numerous VG designs, and its performance was evaluated in the Delft University Low Turbulence Wind Tunnel at a chord‐based Reynolds number of 2×106. Oil‐flow visualizations confirmed the suppression of separation as a result of the vortex‐induced mixing. Further investigation of the oil streaks demonstrated a method to determine the vortex strength. The airfoil performance sensitivity to 41 different VG designs was explored by analysing model and wake pressures. The chordwise positioning, array configuration, and vane height were of prime importance. The sensitivity to vane length, inclination angle, vane shape, and array packing density proved secondary. The VGs were also able to delay stall with simulated airfoil surface roughness. The use of the VG mounting strip was detrimental to the airfoil's performance, highlighting the aerodynamic cost of the commonly used mounting technique. Time‐averaged pressure distributions and the lift standard deviation revealed that the presence of VGs increases load fluctuations in the stalling regime, compared with the uncontrolled case.

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“…Notwithstanding, the observed influence of spacing is relatively low compared with other parameters, in agreement with previous observations on CoR and CtR arrays. ()…”

Section: Resultsmentioning

confidence: 99%

“…However, applied parametric studies of airfoils equipped with VGs are uncommon. Fouatih et al recently conducted a parametric study on a slender 15 % ‐thick NACA4415 airfoil with delta vane devices at a chord‐based Reynolds number Re c =2×10 5 . The authors observed low sensitivity to the VG packing density ( d and D ).…”

Section: Introductionmentioning

confidence: 96%

Experimental parameter study for passive vortex generators on a 30% thick airfoil

et al. 2018

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“…(5) ( 6 ) ( 7 ) hts is the test section height, K1 is the wind tunnel correction constant for solid blockage (0.74 for airfoils), Mv is the model volume, and Aa is the test section area.…”

Section: Data Correctionsmentioning

confidence: 99%

“…Yaw angle is the angle of the VG with respect to the freestream flow as depicted in Fig. 1 where the optimum angle is potentially around 11 o [7]. Active VGs, on the other hand, requires energy throughout its operation such as the blowing jet VG.…”

Section: Introductionmentioning

confidence: 99%

“…In order to minimise drag, micro-VGs having height less than half the boundary layer thickness were designed which performed better by generating weaker vortices just adequately strong to transfer momentum and overcome flow separation more efficiently without inducing parasitic drag [6]. In [7] claimed up to 15% increase in maximum lift coefficient and 3 o delay in stall angle for a NACA 4415 airfoil implemented with counter rotating passive VGs.…”

Section: Introductionmentioning

confidence: 99%

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The potential of hybrid micro-vortex generators to control flow separation of NACA 4415 airfoil in subsonic flow

Jumahadi¹,

Saad²,

Idris³

et al. 2018

AIP Conference Proceedings

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Abstract. Boundary layer separation is detrimental to the lift and drag of most aeronautical applications. Many vortex generators (VG), both passive and active have been designed to reduce these drawbacks. This study targets to investigate the effectiveness of hybrid micro-VGs, which combine both active and passive micro-VGs in controlling separation under subsonic conditions. NACA 4415 airfoils installed with passive, active and hybrid micro-VGs each are designed, 3D printed, and tested in a wind tunnel at 26.19 m/s under Re = 2.5x10 5 . The lift and drag measurements from a 3-component force balance prove that hybrid micro-VGs increase lift by up to 21.2%, increase drag by more than 11.3% and improve lift-to-drag ratio by at least 8.6% until up to 33.7%. From this research, it is believed that hybrid micro-VGs are competitive to the performance of active VGs and a better configuration is to be considered to reduce parasitic drag and outstand active VGs.

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An integral boundary layer engineering model for vortex generators implemented in XFOIL

2018

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To assess and optimize vortex generators (VGs) for flow separation control, the effect of these devices should be modelled in a cost and time efficient way. Therefore, it is of interest to extend integral boundary layer models to analyse the effect of VGs on airfoil performance. In this work, the turbulent boundary layer formulation is modified using a source term approach. An additional term is added to the shear-lag equation, to account for the increased dissipation due to streamwise vortex action in the boundary layer, forcing transition at the VG leading edge where applicable. The source term is calibrated and a semi-empirical relation is set up and implemented in XFOIL. The modified code is capable of addressing the effect of the VG height, length, inflow angle, and chordwise position on the airfoil's aerodynamic properties. The predicted polars for airfoils with VGs show a good agreement with reference data, and the code robustness is demonstrated by assessing different airfoil families at a wide range of Reynolds numbers. KEYWORDSintegral boundary layer, separation control, source term, vortex generator, Xfoil INTRODUCTIONFor the next generation of wind turbines, manufacturers aim to design multimegawatt rotors to improve the competitiveness of wind energy technology. To up-scale wind turbines, novel technologies are required and new design challenges will appear. One such aerodynamic challenge is the management of separated flow. Preventing or at least delaying separation over the blades can positively affect the annual energy production (AEP).On top of that, the magnitude and severe variations of the aerodynamic loads associated with separating flows can be reduced, mitigating structural fatigue issues. In the wind energy industry, separation control is often realized by using passive vortex generators (VGs).Vortex generators improve the resistance of a boundary layer against flow separation by re-energizing the flow close to the surface. The streamwise vortices shed from the free tips of the VGs enhance mixing between the high-energy flow in the outer part of the boundary layer with the low-energy regions near the walls (see Schubauer and Spangenberg. 1 ) The physics involved is nontrivial and poses a number of modelling challenges.To achieve a cost-effective scale up of current turbines, it will become necessary to evolve towards a multidisciplinary design process where VGs are already incorporated early in the design phase. To assess and optimize the use of VGs, there will be a need to effectively model these devices in a cost and time efficient manner. BackgroundNumerous VG modelling techniques have been explored in literature, most of which use computational fluid dynamics (CFD). The most direct and intuitive approach is to model the effect of VGs by including them as a local geometrical protrusion in the domain. This approach requires a fully . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...

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Design optimization of the aerodynamic passive flow control on NACA 4415 airfoil using vortex generators

Cited by 84 publications

References 19 publications

Experimental parameter study for passive vortex generators on a 30% thick airfoil

Experimental parameter study for passive vortex generators on a 30% thick airfoil

The potential of hybrid micro-vortex generators to control flow separation of NACA 4415 airfoil in subsonic flow

An integral boundary layer engineering model for vortex generators implemented in XFOIL

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