Investigation of Blowing and Suction for Turbulent Flow Control on Airfoils

Fahland, Georg; Stroh, Alexander; Atzori, Marco; Vinuesa, Ricardo; Schlatter, Philipp; Gatti, Davide

doi:10.2514/1.j060211

Cited by 21 publications

(28 citation statements)

References 39 publications

(64 reference statements)

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“…The incompressible RANS of the flow around the same NACA4412 airfoil is carried out based on the setup of Fahland et al [25]. This employs the simpleFoam solver from OpenFOAM simulation framework [37].…”

Section: Drag Assessment For Flows Around Airfoilsmentioning

confidence: 99%

“…The compressible RANS simulations also consider the NACA4412 airfoil and are performed with the density-based steady-state solver from the open source CFD software SU2 [39]. As for the incompressible case, the Menter k-ω-SST model is employed, whereas the grid generation system, size and resolution for a given Reynolds number are the same as in Fahland et al [25], as well as the forced transition strategy, which imposes transition at x/c = 0.1. The fluid is modeled as standard air treated as an ideal gas with constant viscosity.…”

Section: Drag Assessment For Flows Around Airfoilsmentioning

confidence: 99%

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Drag Assessment for Boundary Layer Control Schemes with Mass Injection

Fahland

Atzori

Frede

et al. 2023

Preprint

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The present study considers uniform blowing in turbulent boundary layers as active flow control scheme for drag reduction on airfoils. The focus lies on the important question of how to quantify the drag reduction potential of this control scheme correctly. It is demonstrated that mass injection causes the body drag (the drag resulting from the stresses on the body) to differ from the wake survey drag (the momentum deficit in the wake of an airfoil), which is classically used in experiments as a surrogate for the former. This difference is related to the boundary layer control (BLC) penalty, an unavoidable drag portion which reflects the effort of a mass-injecting boundary layer control scheme. This is independent of how the control is implemented. With an integral momentum budget, we show that for the present control scheme, the wake survey drag contains the BLC penalty and is thus a measure for the inclusive drag of the airfoil, i.e. the one required to determine net drag reduction. The concept of the inclusive drag is extended also to boundary layers using the von Kàrmàn equation. This means that with mass injection the friction drag only is not sufficient to assess drag reduction also in canonical flows. Large Eddy Simulations and Reynolds-averaged Navier-Stokes simulations of the flow around airfoils are utilized to demonstrate the significance of this distinction for the scheme of uniform blowing. When the inclusive drag is properly accounted for, control scenarios previously considered to yield drag reduction actually show drag increase.

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Section: Drag Assessment For Flows Around Airfoilsmentioning

confidence: 99%

Section: Drag Assessment For Flows Around Airfoilsmentioning

confidence: 99%

Drag Assessment for Boundary Layer Control Schemes with Mass Injection

Fahland

Atzori

Frede

et al. 2023

Preprint

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show abstract

“…This implies reducing the force parallel to the incoming flow (the drag), and one of the strategies to achieve such a reduction is to perform flow control. A wide range of methods aimed at controlling the flow to reduce the drag have been reported, and some have documented net-energy savings, i.e., taking into account the energy spent on the control, as documented by Fahland et al [8]. These strategies include passive methods, such as riblets [9], which are drag-reducing surfaces proven to be successful in passenger aircraft [10], and active techniques, in which the drag reduction effect is achieved through an action that requires additional energy to be transferred to the flow [11].…”

Section: Introductionmentioning

confidence: 98%

Flow Control in Wings and Discovery of Novel Approaches via Deep Reinforcement Learning

Vinuesa

Lehmkuhl

Lozano-Durán

et al. 2022

Fluids

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In this review, we summarize existing trends of flow control used to improve the aerodynamic efficiency of wings. We first discuss active methods to control turbulence, starting with flat-plate geometries and building towards the more complicated flow around wings. Then, we discuss active approaches to control separation, a crucial aspect towards achieving a high aerodynamic efficiency. Furthermore, we highlight methods relying on turbulence simulation, and discuss various levels of modeling. Finally, we thoroughly revise data-driven methods and their application to flow control, and focus on deep reinforcement learning (DRL). We conclude that this methodology has the potential to discover novel control strategies in complex turbulent flows of aerodynamic relevance.

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“…Fahland et al. (2021) demonstrated the potential of blowing on the pressure side under various conditions, achieving a maximum total net drag saving of 14 %. Kornilov (2021) carried out an experimental study of blowing/suction on two-dimensional low-speed airfoils, and provided ideal estimates of the power spent for actuation.…”

Section: Introductionmentioning

confidence: 99%

“…They found that the wing efficiency improves up to 11 % when uniform suction is applied to the suction side, leading to friction drag increase, but pressure drag reduction. Fahland et al (2021) demonstrated the potential of blowing on the pressure side under various conditions, achieving a maximum total net drag saving of 14 %. Kornilov (2021) carried out an experimental study of blowing/suction on two-dimensional low-speed airfoils, and provided ideal estimates of the power spent for actuation.…”

Section: Introductionmentioning

confidence: 99%

Drag reduction on a transonic airfoil

et al. 2022

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Flow control for turbulent skin-friction drag reduction is applied to a transonic airfoil to improve its aerodynamic performance. The study is based on direct numerical simulations (with up to 1.8 billion cells) of the compressible turbulent flow around a supercritical airfoil, at Reynolds and Mach numbers of $Re_\infty = 3 \times 10^{5}$ and $M_\infty =0.7$ . Control via spanwise forcing is applied over a fraction of the suction side of the airfoil. Besides locally reducing friction, the control modifies the shock wave and significantly improves the aerodynamic efficiency of the airfoil by increasing lift and decreasing drag. Hence, the airfoil can achieve the required lift at a lower angle of attack and with a lower drag. Estimates at the aircraft level indicate that substantial savings are possible; when control is active, its energy cost becomes negligible thanks to the small application area. We suggest that skin-friction drag reduction should be considered not only as a goal, but also as a tool to improve the global aerodynamics of complex flows.

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Investigation of Blowing and Suction for Turbulent Flow Control on Airfoils

Cited by 21 publications

References 39 publications

Drag Assessment for Boundary Layer Control Schemes with Mass Injection

Drag Assessment for Boundary Layer Control Schemes with Mass Injection

Flow Control in Wings and Discovery of Novel Approaches via Deep Reinforcement Learning

Drag reduction on a transonic airfoil

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