Passive control of the flow around unsteady aerofoils using a self-activated deployable flap

Rosti, Marco E.; Omidyeganeh, Mohammad; Pinelli, Alfredo

doi:10.1080/14685248.2017.1314486

Cited by 26 publications

(18 citation statements)

References 51 publications

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“…Initially, the flap is rested at an angle of 5 • from the airfoil surface, which is taken as the undeformed (zero stress) deflection angle. As the vortex shedding process occurs, the flap passively deploys and interacts with the flow, providing significant lift improvements compared to the flap-less case [30,31]. For the multi-domain approach for far-field boundary conditions, five grids of increasing coarseness are used where the finest and coarsest grid levels are [−0.…”

Section: Passively Deployed Flap On An Airfoil 521 Problem Descriptionmentioning

confidence: 99%

A strongly coupled immersed boundary method for fluid-structure interaction that mimics the efficiency of stationary body methods

Nair¹,

Goza²

2021

Preprint

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Strongly coupled immersed boundary (IB) methods solve the nonlinear fluid and structural equations of motion simultaneously for strongly enforcing the no-slip constraint on the body. Handling this constraint requires solving several large dimensional systems that scale by the number of grid points in the flow domain even though the nonlinear constraints scale only by the small number of points used to represent the fluid-structure interface. These costly large scale operations for determining only a small number of unknowns at the interface creates a bottleneck to efficiently time-advancing strongly coupled IB methods. In this manuscript, we present a remedy for this bottleneck that is motivated by the efficient strategy employed in stationary-body IB methods while preserving the favorable stability properties of strongly coupled algorithms-we precompute a matrix that encapsulates the large dimensional system so that the prohibitive large scale operations need not be performed at every time step. This precomputation process yields a modified system of small-dimensional constraint equations that is solved at minimal computational cost while time advancing the equations. We also present a parallel implementation that scales favorably across multiple processors. The accuracy, computational efficiency and scalability of our approach are demonstrated on several two dimensional flow problems. Although the demonstration problems consist of a combination of rigid and torsionally mounted bodies, the formulation is derived in a more general setting involving an arbitrary number of rigid, torsionally mounted, and continuously deformable bodies.

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Section: Passively Deployed Flap On An Airfoil 521 Problem Descriptionmentioning

confidence: 99%

A strongly coupled immersed boundary method for fluid-structure interaction that mimics the efficiency of stationary body methods

Nair¹,

Goza²

2021

Preprint

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“…Thus, the wing can be prevented from an abrupt increase in the angle of attack because of perching maneuvers or gusts. Rosti et al [59] investigated physical mechanism of the flow field over NACA0020 airfoil having an elastically mounted flap at Reynolds number of 2 × 10 4 .…”

Section: Self-activated Deployable Flapmentioning

confidence: 99%

Traditional and New Types of Passive Flow Control Techniques to Pave the Way for High Maneuverability and Low Structural Weight for UAVs and MAVs

Genç¹,

Koca²,

Demir³

et al. 2020

Autonomous Vehicles

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Prevailing utilization of airfoils in the design of micro air vehicles and wind turbines causes to gain attention in terms of determination of flow characterization on these flight vehicles operating at low Reynolds numbers. Thus, these vehicles require flow control techniques to reduce flow phenomena such as boundary layer separation or laminar separation bubble (LSB) affecting aerodynamic performance negatively. This chapter presents a detailed review of traditional passive control techniques for flight vehicle applications operating at low Reynolds numbers. In addition to the traditional methods, a new concept of the pre-stall controller by means of roughness material, flexibility and partial flexibility is highlighted with experimental and numerical results. Results indicate that passive flow control methods can dramatically increase the aerodynamic performance of the aforementioned vehicles by controlling the LSB occurring in the pre-stall region. The control of the LSB with new concept pre-stall control techniques provides lift increment and drag reduction by utilizing significantly less matter consumption and low energy. In particular, new types of these methods presented for the first time by the chapter's authors have enormously influenced the progress of separation and LSB, resulting in postponing of the stall and enhancing the aerodynamic performance of wind turbine applications.

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“…1 and 2, are discretised on a cell-centred, co-located grid using a well-established curvilinear finite volume code [19–22]. The fluxes are approximated by a second-order central formulation, and the method of Rhie and Chow [23] is used to avoid spurious pressure oscillations.…”

Section: Baseline Numerical Formulationmentioning

confidence: 99%

Numerical Simulation of a Passive Control of the Flow Around an Aerofoil Using a Flexible, Self Adaptive Flaplet

Rosti

Omidyeganeh

Pinelli

2018

Flow Turbulence Combust

Self Cite

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Self-activated feathers are used by almost all birds to adapt their wing characteristics to delay stall or to moderate its adverse effects (e.g., during landing or sudden increase in angle of attack due to gusts). Some of the feathers are believed to pop up as a consequence of flow separation and to interact with the flow and produce beneficial modifications of the unsteady vorticity field. The use of self adaptive flaplets in aircrafts, inspired by birds feathers, requires the understanding of the physical mechanisms leading to the mentioned aerodynamic benefits and the determination of the characteristics of optimal flaps including their size, positioning and ideal fabrication material. In this framework, this numerical study is divided in two parts. Firstly, in a simplified scenario, we determine the main characteristics that render a flap mounted on an aerofoil at high angle of attack able to deliver increased lift and improved aerodynamic efficiency, by varying its length, position and its natural frequency. Later on, a detailed direct numerical simulation analysis is used to understand the origin of the aerodynamic benefits introduced by the flaplet movement induced by the interaction with the flow field. The parametric study that has been carried out, reveals that an optimal flap can deliver a mean lift increase of about 20% on a NACA0020 aerofoil at an incidence of 20o degrees. The results obtained from the direct numerical simulation of the flow field around the aerofoil equipped with the optimal flap at a chord Reynolds number of 2 × 104 shows that the flaplet movement is mainly induced by a cyclic passage of a large recirculation bubble on the aerofoil suction side. In turns, when the flap is pushed downward, the induced plane jet displaces the trailing edge vortices further downstream, away from the wing, moderating the downforce generated by those vortices and regularising the shedding cycle that appears to be much more organised when the optimal flaplet configuration is selected.

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Passive control of the flow around unsteady aerofoils using a self-activated deployable flap

Cited by 26 publications

References 51 publications

A strongly coupled immersed boundary method for fluid-structure interaction that mimics the efficiency of stationary body methods

A strongly coupled immersed boundary method for fluid-structure interaction that mimics the efficiency of stationary body methods

Traditional and New Types of Passive Flow Control Techniques to Pave the Way for High Maneuverability and Low Structural Weight for UAVs and MAVs

Numerical Simulation of a Passive Control of the Flow Around an Aerofoil Using a Flexible, Self Adaptive Flaplet

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