Active Control of Performance and Vibratory Loads Using Leading Edge Slats

2012 ◽  
Author(s):  
Kumar Ravichandran ◽  
Inderjit Chopra
Keyword(s):  
Active Control ◽  
Leading Edge ◽  
Leading Edge Slats

The Dassault Mirage G

1969 ◽  
Vol 73 (708) ◽  
pp. 1027-1028
Author(s):  
Henri Deplante
Keyword(s):  
Leading Edge ◽  
Variable Geometry ◽  
Relative Thickness ◽  
Trailing Edge ◽  
High Lift ◽  
Profound Knowledge ◽  
Subsonic Speed ◽  
Trailing Edge Flaps ◽  
Leading Edge Slats

The interest of wings with variable sweepback springs directly from pure commonsense and appeals to no profound knowledge of aerodynamics for its justification. To realise the advantage of variable geometry, it is enough to know that only a wing of small relative thickness is capable of good performance at supersonic speeds and that by increasing the sweepback from 20° to 70° the thickness of a wing is divided by about 2. In the advanced position, the wing offers its full span to the airstream and with high-lift devices in action (leading-edge slats and trailing-edge flaps combined), the aeroplane can develop the considerable lift necessary for take-off and landing as well as for break-through and for slow approach. Wings still advanced but slats, flaps and undercarriage retracted, the aeroplane is in excellent maximum fineness condition for protracted cruising at subsonic speed or for a long wait. As soon as transonic (Mach No of more than 0-8) or supersonic speeds are in question, the wings are progressively folded back.

scholarly journals A NEW ACTIVE CONTROL STRATEGY FOR WIND-TURBINE BLADES UNDER OFF-DESIGN CONDITIONS

2012 ◽  
Vol 19 ◽  
pp. 283-292 ◽  
Author(s):  
RI-KUI ZHANG ◽  
JIE-ZHI WU ◽  
SHI-YI CHEN
Keyword(s):  
Wind Turbine ◽  
Active Control ◽  
Turbine Blades ◽  
Leading Edge ◽  
Operating Conditions ◽  
Wind Turbine Blades ◽  
Delta Wings ◽  
Control Units ◽  
Shaft Torque ◽  
Active Control Strategy

A new active control strategy for wind-turbine blades under off-design conditions has been investigated in this paper. According to our previous work, in comparison with the traditional straight leading-edge blade, a new kind of bionic blades with a sinusoidal leading edge can significantly enhance the turbine's power output at high speed inflows. However, the wavy leading-edge shape is unfavorable under the design operating conditions since an early boundary-layer separation is inevitable for a wind-turbine blade because of the geometric disturbances of the leading-edge tubercles. But for the present active control, the deflect in wavy leading-edge blades can be eliminated by introducing a series of small flat delta wings as the control units, since delta wings can also generate powerful leading-edge vortices. As a preliminary test, our numerical results show that, the shaft-torque fluctuation in the turbine's stall region can be improved from 27.8% for a straight leading-edge blade (no control) to 8.9% for the present active control; and by adjusting the control parameters, the control units nearly have not any negative effect on the blade's shaft torque under the design conditions. We believe that, as an auxiliary tool of the conventional control strategies, the present active control approach may be favorable to generate a more stable and more controllable power output for wind turbines under all operating conditions (even in the yawed inflows).

A Natural Evolution Based Numerical Optimisation Framework to Develop and Enhance Airfoil-Slat Arrangement

2019 ◽  
Author(s):  
Sushrut Kumar ◽  
Priyam Gupta ◽  
Raj Kumar Singh
Keyword(s):  
Genetic Algorithm ◽  
Fitness Function ◽  
Fuel Efficiency ◽  
Optimal Solution ◽  
Leading Edge ◽  
Initial Population ◽  
Invasive Weed ◽  
Fitness Value ◽  
Leading Edge Slats ◽  
Dynamics Simulations

Abstract Leading Edge Slats are popularly being put into practice due to their capability to provide a significant increase in the lift generated by the wing airfoil and decrease in the stall. Consequently, their optimum design is critical for increased fuel efficiency and minimized environmental impact. This paper attempts to develop and optimize the Leading-Edge Slat geometry and its orientation with respect to airfoil using Genetic Algorithm. The class of Genetic Algorithm implemented was Invasive Weed Optimization as it showed significant potential in converging design to an optimal solution. For the study, Clark Y was taken as test airfoil. Slats being aerodynamic devices require smooth contoured surfaces without any sharp deformities and accordingly Bézier airfoil parameterization method was used. The design process was initiated by producing an initial population of various profiles (chromosomes). These chromosomes are composed of genes which define and control the shape and orientation of the slat. Control points, Airfoil-Slat offset and relative chord angle were taken as genes for the framework and different profiles were acquired by randomly modifying the genes within a decided design space. To compare individual chromosomes and to evaluate their feasibility, the fitness function was determined using Computational Fluid Dynamics simulations conducted on OpenFOAM. The lift force at a constant angle of attack (AOA) was taken as fitness value. It was assigned to each chromosome and the process was then repeated in a loop for different profiles and the fittest wing slat arrangement was obtained which had an increase in CL by 78% and the stall angle improved to 22°. The framework was found capable of optimizing multi-element airfoil arrangements.

scholarly journals Active Control of a Stalled Airfoil Through Steady or Unsteady Actuation Jets

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
V. G. Chapin ◽  
E. Benard
Keyword(s):  
Active Control ◽  
Computational Study ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Position Angle ◽  
Navier Stokes ◽  
Suction Surface ◽  
Parametric Studies ◽  
Naca 0012

The active control of the leading-edge (LE) separation on the suction surface of a stalled airfoil (NACA 0012) at a Reynolds number of 106 based on the chord length is investigated through a computational study. The actuator is a steady or unsteady jet located on the suction surface of the airfoil. Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations are solved on hybrid meshes with the Spalart–Allmaras turbulence model. Simulations are used to characterize the effects of the steady and unsteady actuation on the separated flows for a large range of angle of attack (0 < α < 28 deg). Parametric studies are carried out in the actuator design-space to investigate the control effectiveness and robustness. An optimal actuator position, angle, and frequency for the stalled angle of attack α = 19 deg are found. A significant increase of the lift coefficient is obtained (+ 84% with respect to the uncontrolled reference flow), and the stall is delayed from angle of attack of 18 deg to more than 25 deg. The physical nonlinear coupling between the actuator position, velocity angle, and frequency is investigated. The critical influence of the actuator location relative to the separation location is emphasized.

Active Control of Unsteady Cavitating Flows Over Hydrofoil

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Maria Grazia De Giorgi ◽  
Donato Fontanarosa ◽  
Antonio Ficarella
Keyword(s):  
Active Control ◽  
Leading Edge ◽  
Suction Side ◽  
Synthetic Jet ◽  
Thick Sheet ◽  
Dimensionless Frequency ◽  
Ambient Conditions ◽  
Local Pressure ◽  
Vapor Cavity ◽  
Momentum Coefficient

Abstract A preliminary two-dimensional (2D) numerical investigation of the active control of unsteady cavitation by means of one single synthetic jet actuator (SJA) is presented. The investigation involves the cloud-cavitating flow of water around a NACA 0015 hydrofoil with an angle of attack of 8-deg and ambient conditions. The SJA locates on the suction side at a distance of 16% of the chord from the leading edge; it has been modeled by means of a user-defined velocity boundary conditions based on a sinusoidal waveform. A Eulerian homogeneous mixture model has been used, coupled with an extended Schnerr–Sauer cavitation model and a volume of fluid interface tracking method. As first, a sensitivity analysis allowed to evaluate the influence of the main control parameters, namely, the momentum coefficient Cμ, the dimensionless frequency F+, and the jet angle αjet. As a result, the best performing SJA configuration was retrieved at Cμ=0.0002, F+=0.309, and αjet=90 deg, which led to a reduction of both the average vapor content and the average torsional load in the measure of 34.6% and 17.8%. The analysis of the coupled dynamics between vapor cavity–vorticity and their proper orthogonal decomposition (POD)-based modal structures highlighted the benefit of the SJA lies in preventing the growth of a thick sheet cavity, which causes the development of the highly cavitating cloud dynamics after the cavity breakup. This is mainly due to an additional vorticity close to the hydrofoil surface just downstream the SJA, as well as a local pressure modification close the SJA during the blowing stroke.

Active Control of Flow Separation Over a NACA0024 Airfoil by DBD Plasma Actuator and FBG Sensor

2011 ◽  
Author(s):  
Seth Walker ◽  
Takehiko Segawa ◽  
Timothy Jukes ◽  
Hirohide Furutani ◽  
Norihiko Iki ◽  
...  
Keyword(s):  
Active Control ◽  
Flow Separation ◽  
Leading Edge ◽  
Open Circuit ◽  
Flow Conditions ◽  
Dbd Plasma ◽  
Flow Separation Control ◽  
Barrier Discharge Plasma ◽  
Tunnel Analysis ◽  
Control Of Flow

Dielectric barrier discharge plasma actuators (DBD-PA) and fiber Bragg grating flow sensors (FBG-FS) have been investigated for active control of flow separation around a NACA0024 airfoil. Tangential jets were produced in the vicinity of the DBD-PA slightly aft of the leading edge of the airfoil. The flow separation control ability was evaluated at a low Reynolds number, Re = 5.0×104, in an open-circuit wind tunnel. Analysis of instantaneous and time-averaged velocity distributions around the airfoil was achieved using a particle image velocimetry (PIV) system. The flow conditions induced by the DBD-PA to suppress the flow separation were found for angles of attack of α = 8°, 12°, and 16°. When unaided by the DBD-PA system, flow separations from NACA0024 airfoil are suppressed significantly for certain Reynolds numbers and angles of attack. FBG-FS attached a chord-wise cantilever near the trailing edge of the airfoil was used to measure strain fluctuations for its feasibility to detect flow separation in real time and construct feedback control system with DBD-PA. In this study, it was found that standard deviations of strain fluctuations increase obviously in cases of flow conditions at which the flow around NACA0024 airfoil separates.

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