A large-eddy simulation on a deep-stalled aerofoil with a wavy leading edge

Pérez-Torró, Rafael; Kim, Jae Wook

doi:10.1017/jfm.2016.841

Cited by 72 publications

(23 citation statements)

References 33 publications

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“…The performance improvement is driven by the modified flow field at the leading edge. Previous studies 20,21,[23][24][25] agree that the flow tends to separate at the troughs, while it remains attached at the peaks. Separated flow in the trough area is followed by a reattachment further downstream forming a laminar separation bubble.…”

Section: Introductionmentioning

confidence: 68%

“…In this work, h LE = 0.0125L c and λ LE = 0.05L c (Figure 1c), thus only one wavelength is considered for now. The amplitude is chosen consistent with previous large eddy simulations in low speed flows 20,36 . The amplitude has to be limited using a laminar supercritical aerofoil in order to not loose the benefits of the laminar boundary layer.…”

Section: A Geometry and Discretisation Of The Problemmentioning

confidence: 99%

“…Wavy leading edges can be described as 'smart' vortex generators because they create counter-rotating streamwise vortices at the trough 20,21 , without introducing discontinuity in the aerofoil geometry. It has been observed 22 that streamwise BL streaks can attenuate disturbances and delay the L-T transition.…”

Section: Introductionmentioning

confidence: 99%

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An investigation on a supercritical aerofoil with a wavy leading edge in a transonic flow

Degregori

Kim

2020

Physics of Fluids

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A compressible large-eddy simulation is performed to study the effects of a wavy leading edge (WLE) applied on a supercritical aerofoil in a transonic flow at Re∞ = 5.0 × 105 and M∞ = 0.7. The wavelength and peak-to-trough amplitude of the WLE used in this study are 5% and 2.5%, respectively, of the mean aerofoil chord. The primary aim of this study is to understand the aerodynamic characteristics of the modified aerofoil over a range of incidence angles. For this reason, a slow heaving motion is imposed where the geometric angle of attack is gradually increased from αg = 2° to 7° without a significant dynamic (added mass) effect, i.e., a quasi-linear range. The new transonic flow study shows significantly different findings (with some similar features) to the previous low-speed flow studies. It is observed in the quasi-linear range that the modified aerofoil achieves a performance improvement at low and moderate angles because of a drag reduction in the leading edge region and downstream of the laminar–turbulent (L–T) transition point. The leading edge (LE) analysis shows that the maximum pressure coefficient remains equal to that of the baseline case only at the trough and peak sections. The relative decrease in pressure at the LE results in the drag reduction. The transonic flow at the LE is analyzed in further detail to show a reversed flow region at the trough and its influence on the boundary layer development over the aerofoil. In addition, the spanwise variation of the boundary layer characteristics over the modified aerofoil is evaluated and analyzed. One of the most notable findings in this paper is that the flow at the trough becomes supersonic even at low angles of attack, and this results in an enhanced LE flow acceleration spread across the span, which seems facilitated by using a short WLE wavelength. This flow behavior is qualitatively explained by using an analogy between a channeling effect and a convergent–divergent nozzle in a transonic flow. Another notable observation is that there is an upstream movement of the laminar–turbulent transition point seemingly related to the flow distortion around the WLE. Interestingly, the flow distortion introduces a three dimensionality into the laminar boundary layer, but it keeps the flow laminar, so the benefits of the laminar supercritical aerofoil are not lost. These LE phenomena have a major impact on the shock structure at high incidence angles where the more energetic laminar boundary layer changes the shock structure over the modified aerofoil. This can be crucial to control the shock buffet phenomenon.

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Section: Introductionmentioning

confidence: 68%

Section: A Geometry and Discretisation Of The Problemmentioning

confidence: 99%

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An investigation on a supercritical aerofoil with a wavy leading edge in a transonic flow

Degregori

Kim

2020

Physics of Fluids

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“…7b show a tubercled formation at the leading edge of the model (see the zoom in the circle). The streamwise actuation seems to recreates a virtual tubercled leading edge surface which its beneficial effect on stalled aerofoils are studied, among others, in [26][27][28]. The energy of the flow necessary to win the adverse pressure gradient, created by the front curvature, can be measured by looking at the streamwise velocity profiles collected along the rounded edge of the model.…”

Section: Best Vertical Slot Vs Streamwise Slot Actuationmentioning

confidence: 99%

Active Aerodynamic Control of a Separated Flow Using Streamwise Synthetic Jets

Minelli

Tokarev

Zhang

et al. 2019

Flow Turbulence Combust

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LES simulations at Re = 1 × 10 5 and wind tunnel experiments at Re = 5 × 10 5 were conducted to investigate the beneficial effect of an active flow control (AFC) technique on the aerodynamic performance of a simplified truck geometry. The paper involves the investigation of a synthetic jet actuator characterized by periodic blowing and suction that defines a zero net mass flux flow control mechanism. The actuation aims to suppress the flow separation occurring at the A-pillar (front rounded corner) of a truck cabin. The work flow is defined as it follows. First, LES at low Reynolds number are conducted for different disposition of the actuation slots. The results show a beneficial effect when the actuation slots are positioned in streamwise direction compared to spanwise (vertical) direction. Second, based on the previous considerations, wind tunnel experiments are conducted to verify and support the numerical findings. Both numerical solutions and experimental data show the same trend and the superiority of the streamwise slots actuation when compared to traditional vertical slot actuation. In particular, this work shows the weakness of a vertical slot actuation, when its location is not optimized. A small change in its positioning greatly worsen the efficacy of the separation control in terms of drag reduction and separation bubble length. The slot location directly affects the length of the separated flow region which its reduction can vary between 40-70% based on the positioning. Conversely, a streamwise actuation, spanning a larger portion of the curvature of a rounded A-pillar, is not affected by this behaviour and contributes up to 80% of the recirculation bubble reduction measured in the unactuated case. The effect of the location change and the orientation of a zero net mass flux jet slot is therefore investigated and discussed in this work.

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“…For airfoils with a blunt leading and/or trailing edges, wavy or serrated shapes are usually effective to suppress the formation of vortex shedding. Pérez-Torró and Kim [19] performed a large-eddy simulation on a deep-stalled airfoil with a wavy leading edge, revealing that an increased lift and a decreased drag were achieved by using the wavy leading edge compared to the straight leading edge. Additionally, the wavy leading edge significantly reduced the fluctuating component of aerodynamic forces at the frequency of the periodic vortex shedding.…”

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confidence: 99%

Control of cylinder wake flow and noise through a downstream porous treatment

Mao

2019

Aerospace Science and Technology

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Various passive and active methods have been developed to control flow separation from bluff bodies. However, these methods require adjusting features of the solid surface, such as modifying its geometry or porosity, or applying external force or momentum. This paper develops an off-body-based method, without adjusting any features of the solid surface, for controlling the unsteady flow separation by fixing porous materials downstream of bluff bodies. Numerical study on flow past a circular cylinder at a subcritical Reynolds number is performed, and the result indicates that the added downstream porous material changes flow in the wake and re-laminarizes the turbulent flow around the curved cylinder surface, reducing the wall pressure fluctuation around the cylinder. therefore, the associated aerodynamic noise is reduced greatly.

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A large-eddy simulation on a deep-stalled aerofoil with a wavy leading edge

Cited by 72 publications

References 33 publications

An investigation on a supercritical aerofoil with a wavy leading edge in a transonic flow

An investigation on a supercritical aerofoil with a wavy leading edge in a transonic flow

Active Aerodynamic Control of a Separated Flow Using Streamwise Synthetic Jets

Control of cylinder wake flow and noise through a downstream porous treatment

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