scholarly journals An investigation of unsteady 3D effects on trailing edge flaps

2016 ◽  
Author(s):  
Eva Jost ◽  
Annette Fischer ◽  
Galih Bangga ◽  
Thorsten Lutz ◽  
Ewald Krämer
Keyword(s):  
Trailing Edge ◽  
Trailing Vortices ◽  
Trailing Edge Flaps ◽  
Negative Effect ◽  
3D Effects ◽  
Computational Fluid Dynamics Cfd ◽  
Trailing Edge Flap ◽  
The Impact ◽  
2D Airfoil ◽  
High Influence

Abstract. The present study investigates the impact of unsteady and viscous 3D aerodynamic effects on a wind turbine blade with trailing edge flap by means of Computational Fluid Dynamics (CFD). Harmonic oscillations are simulated on the DTU 10 MW rotor with a morphing flap of 10 % chord extent ranging from 70 % to 80 % blade radius. The deflection frequency is varied in the range between 1 p and 6 p. To quantify 3D effects, rotor simulations are compared to 2D airfoil computations and the 2D theory by Theodorsen. A significant influence of trailing and shed vortex structures has been found which leads to an amplitude reduction and hysteresis of the lift response in the flap section with regard to the deflection signal. For the 3D rotor results greater amplitude reductions and a less pronounced hysteresis is observed compared to the 2D airfoil case. Blade sections neighboring the flap experience however an opposing impact and hence partly compensate the negative effect of trailing vortices in the flap section in respect to integral loads. The comparison to steady flap deflections at the 3D rotor revealed the high influence of dynamic inflow effects.

scholarly journals An investigation of unsteady 3-D effects on trailing edge flaps

2017 ◽  
Vol 2 (1) ◽  
pp. 241-256 ◽  
Author(s):  
Eva Jost ◽  
Annette Fischer ◽  
Galih Bangga ◽  
Thorsten Lutz ◽  
Ewald Krämer
Keyword(s):  
Near Wake ◽  
Harmonic Oscillations ◽  
Trailing Edge ◽  
Trailing Vortices ◽  
Trailing Edge Flaps ◽  
Negative Effect ◽  
Computational Fluid Dynamics Cfd ◽  
Trailing Edge Flap ◽  
The Impact ◽  
High Influence

Abstract. The present study investigates the impact of unsteady 3-D aerodynamic effects on a wind turbine blade with trailing edge flap by means of computational fluid dynamics (CFD). Harmonic oscillations are simulated on the DTU 10 MW rotor with a morphing flap of 10 % chord extent ranging from 70 to 80 % blade radius. The deflection frequency is varied in the range between 1 and 6 p. To quantify 3-D effects, rotor simulations are compared to 2-D airfoil computations and the 2-D theory by Theodorsen. It was found that the deflection of the flap on the 3-D rotor causes a complex wake development and induction which influences the loads over large parts of the blade. In particular, the rotor near wake with its trailing and shed vortex structures revealed a great impact. Trailing vorticity, a 3-D phenomenon, is caused by the gradient of bound circulation along the blade span. Shed vorticity originates from the temporal bound circulation gradient and is thus also apparent in 2-D. Both lead to an amplitude reduction and shed vorticity additionally to a hysteresis of the lift response with regard to the deflection signal in the flap section. A greater amplitude reduction and a less pronounced hysteresis is observed on the 3-D rotor compared to the 2-D airfoil case. Blade sections neighboring the flap experience, however, an opposing impact and hence partly compensate for the negative effect of trailing vortices in the flap section with respect to integral loads. Comparisons to steady flap deflections at the 3-D rotor revealed the high influence of dynamic inflow effects.

scholarly journals Pressure Based Lift Estimation and its Application to Feedforward Load Control employing Trailing Edge Flaps

2020 ◽  
Author(s):  
Sirko Bartholomay ◽  
Tom T. B. Wester ◽  
Sebastian Perez-Becker ◽  
Simon Konze ◽  
Christian Menzel ◽  
...  
Keyword(s):  
Surface Pressure ◽  
Feedforward Control ◽  
Force Balance ◽  
Estimation Methods ◽  
Load Control ◽  
Trailing Edge ◽  
Trailing Edge Flaps ◽  
Feedforward Controller ◽  
Trailing Edge Flap ◽  
C 30

Abstract. This experimental load control study presents results of an active trailing edge flap feedforward controller for wind turbine applications. The controller input is derived from pressure based lift estimation methods that rely either on a quasi-steady method, based on a three-hole probe, or on an unsteady method that is based on three selected surface pressure ports. Furthermore, a standard feedback controller, based on force balance measurements, is compared to the feedforward control. A Clark-Y airfoil is employed for the wing that is equipped with a trailing edge flap of x/c = 30 % chordwise extension. Inflow disturbances are created by a two-dimensional active grid. The Reynolds number is Re = 290,000 and reduced frequencies of k = 0.07 up to k = 0.32 are analyzed. Within the first part of the paper, the lift estimation methods are compared. The surface pressure based method shows generally more accurate results whereas the three-hole probe estimate overpredicts the lift amplitudes with increasing frequencies. Nonetheless, employing the latter as input to the feedforward controller is more promising as a beneficial phase lead is introduced by this method. A successful load alleviation was achieved up to reduced frequencies of k = 0.192.

Vibration reduction of helicopter with trailing-edge flaps at various flying conditions

2016 ◽  
Vol 231 (4) ◽  
pp. 770-784 ◽  
Author(s):  
SK Kodakkattu ◽  
ML Joy ◽  
K Prabhakaran Nair
Keyword(s):  
Rotor Blade ◽  
Torsional Stiffness ◽  
Trailing Edge ◽  
Control Power ◽  
Surface Method ◽  
Solidity Ratio ◽  
Helicopter Rotor Blade ◽  
Trailing Edge Flaps ◽  
Trailing Edge Flap ◽  
Improved Design

The aim of this study is to find the optimal torsional stiffness and trailing-edge flap locations of the helicopter rotor blade for minimum vibration and flap control power at flap lengths of 6% and 9% of the rotor-blade length. A three level orthogonal array based response surface method using polynomial functions is used to describe both vibration and flap control power. Pareto points minimizing hub vibration and flap control power are found at flap lengths of 6% and 9% of the rotor length. This study also explores the variation in rotor hub vibration and flap control power with flying conditions such as the advance ratio and the thrust-to-solidity ratio at the optimum design points. This gives a useful improved design with about a 60% decrease in hub vibration with a penalization of increased flap power at the normal flying regime of rotor-craft flight.

On power and actuation requirement in swashplateless primary control of helicopters using trailing-edge flaps

2014 ◽  
Vol 118 (1203) ◽  
pp. 503-521
Author(s):  
F. Gandhi ◽  
C. Duling ◽  
F. Straub
Keyword(s):  
Aerodynamic Drag ◽  
Primary Control ◽  
Power Penalty ◽  
Trailing Edge ◽  
Level Flight ◽  
High Speeds ◽  
Steady Level ◽  
Trailing Edge Flaps ◽  
Trailing Edge Flap ◽  
Blade Tips

Abstract This paper examines three specific aspects pertaining to the trailing-edge flap (TEF) enabled swashplateless primary control of a helicopter. The study is based on a utility helicopter very similar to the UH-60A Blackhawk helicopter, with rotor torsion frequency reduced to 2·1/rev, and 20% chord TEFs extending from 70-90% span. The questions addressed in the paper are the power penalty due to aerodynamic drag associated with TEF control, the pitch-index required to limit the range of TEF deflections over variations in aircraft gross-weight and airspeed, and the influence of rotor RPM variation on swashplateless primary control. Results indicate that the power penalty associated with TEF enabled primary control at high speeds is in the range of 6-7%, due to increased drag on the advancing side in the region of the TEFs and at the blade tips. At low to moderate speeds the increase in power is 2-4% on average, more dependent on the pitch-index, and due to drag increase over most of the azimuth in the region of the TEFs. A variation in pitch-index from 16° for lower speeds and gross weights, to 20-22° for higher speeds and gross weights, would reduce the steady level flight TEF defection requirements to under ±3°, leaving sufficient control margin. Increase in rotor RPM does not increase directly increase thrust (as with a stiff-torsion rotor) but reduces the rotating torsion frequency, and together with the increased dynamic pressures increases the sensitivity to TEF control. At low to moderate speeds a 9% increase in RPM reduces the maximum TEF deflections required by about 1°, but is accompanied by a large increase in rotor power. Conversely, a 9% RPM reduction decreases rotor power required, but the TEF defections required increase by 1–1·5°.

Influence of Flap Deflection Angle on Wind Turbine Airfoil with Trailing Edge Flaps

2014 ◽  
Vol 977 ◽  
pp. 222-227
Author(s):  
Ya Lei Jia ◽  
Zhong He Han ◽  
Fu You Li ◽  
Ya Kai Bai ◽  
Ji Xuan Wang
Keyword(s):  
Wind Turbine ◽  
Deflection Angle ◽  
Aerodynamic Performance ◽  
Main Body ◽  
Trailing Edge ◽  
Trailing Edge Flaps ◽  
Wind Turbine Airfoil ◽  
Trailing Edge Flap ◽  
Flap Deflection ◽  
Drag Ratio

To improve the ability of capturing the wind energy of wind turbine and shorten the design period is of great importance to designing wind turbine blade. The article established S809 airfoil model with trailing edge flaps, The gap of the frontal subject and trailing edge flap adopt uniform gap structure, this structure will reduce the influence of the gap on aerodynamic characteristics.Using the k-ω Two equation turbulence model , the article calculated aerodynamic performance of S809 with 10% chord length trailing edge flaps under different deflecting angles. Results show that gap between the main body and trailing edge flap has little effect on airfoil aerodynamic performance, however, the deflection Angle of Trailing edge flap have great affect on airfoil aerodynamic performance, when deflection Angle of trailing edge flap is 14 ° degrees ,the lift-to-drag ratio is the largest.

scholarly journals Identification of Flap Motion Parameters for Vibration Reduction in Helicopter Rotors with Multiple Active Trailing Edge Flaps

2011 ◽  
Vol 18 (5) ◽  
pp. 727-745 ◽  
Author(s):  
Uğbreve;ur Dalli ◽  
Şcedilefaatdin Yüksel
Keyword(s):  
Rotor Blade ◽  
Helicopter Rotor ◽  
System Response ◽  
Trailing Edge ◽  
Blade Root ◽  
Helicopter Rotor Blade ◽  
Blade Vibrations ◽  
Trailing Edge Flaps ◽  
Trailing Edge Flap ◽  
Blade Loads

An active control method utilizing the multiple trailing edge flap configuration for rotorcraft vibration suppression and blade loads control is presented. A comprehensive model for rotor blade with active trailing edge flaps is used to calculate the vibration characteristics, natural frequencies and mode shapes of any complex composite helicopter rotor blade. A computer program is developed to calculate the system response, rotor blade root forces and moments under aerodynamic forcing conditions. Rotor blade system response is calculated using the proposed solution method and the developed program depending on any structural and aerodynamic properties of rotor blades, structural properties of trailing edge flaps and properties of trailing edge flap actuator inputs. Rotor blade loads are determined first on a nominal rotor blade without multiple active trailing edge flaps and then the effects of the active flap motions on the existing rotor blade loads are investigated. Multiple active trailing edge flaps are controlled by using open loop controllers to identify the effects of the actuator signal output properties such as frequency, amplitude and phase on the system response. Effects of using multiple trailing edge flaps on controlling rotor blade vibrations are investigated and some design criteria are determined for the design of trailing edge flap controller that will provide actuator signal outputs to minimize the rotor blade root loads. It is calculated that using the developed active trailing edge rotor blade model, helicopter rotor blade vibrations can be reduced up to 36% of the nominal rotor blade vibrations.

Aerodynamic Aspects of Boundary Layer Control for High Lift at Low Speeds

1963 ◽  
Vol 67 (628) ◽  
pp. 201-223 ◽  
Author(s):  
John Williams ◽  
Sidney F. J. Butler
Keyword(s):  
Boundary Layer ◽  
Leading Edge ◽  
Boundary Layer Control ◽  
Trailing Edge ◽  
High Lift ◽  
Air Jets ◽  
Slot Suction ◽  
Trailing Edge Flaps ◽  
Trailing Edge Flap ◽  
Layer Control

Summary:The usefulness of boundary-layer control (B.L.C.) at the knee of a trailing-edge flap, over the wing nose close to the leading-edge or at the knee of a leading-edge flap is first noted. Various methods of providing B.L.C. are outlined, comprising slot blowing, slot suction, area suction, inclined air-jets, and specially-designed aerofoil shapes. The aerodynamic aspects of slot blowing over trailing-edge flaps and the wing nose are then examined in detail and both slot suction and area suction are also considered. The associated practical design features required for good performance are discussed and some flight-handling implications are mentioned.

scholarly journals Pressure-based lift estimation and its application to feedforward load control employing trailing-edge flaps

2021 ◽  
Vol 6 (1) ◽  
pp. 221-245
Author(s):  
Sirko Bartholomay ◽  
Tom T. B. Wester ◽  
Sebastian Perez-Becker ◽  
Simon Konze ◽  
Christian Menzel ◽  
...  
Keyword(s):  
Surface Pressure ◽  
Feedforward Control ◽  
Force Balance ◽  
Estimation Methods ◽  
Load Control ◽  
Trailing Edge ◽  
Trailing Edge Flaps ◽  
Feedforward Controller ◽  
Trailing Edge Flap ◽  
C 30

Abstract. This experimental load control study presents results of an active trailing-edge flap feedforward controller for wind turbine applications. The controller input is derived from pressure-based lift estimation methods that rely either on a quasi-steady method, based on a three-hole probe, or on an unsteady method that is based on three selected surface pressure ports. Furthermore, a standard feedback controller, based on force balance measurements, is compared to the feedforward control. A Clark-Y airfoil is employed for the wing that is equipped with a trailing-edge flap of x/c=30% chordwise extension. Inflow disturbances are created by a two-dimensional active grid. The Reynolds number is Re=290 000, and reduced frequencies of k=0.07 up to k=0.32 are analyzed. Within the first part of the paper, the lift estimation methods are compared. The surface-pressure-based method shows generally more accurate results, whereas the three-hole probe estimate overpredicts the lift amplitudes with increasing frequencies. Nonetheless, employing the latter as input to the feedforward controller is more promising as a beneficial phase lead is introduced by this method. A successful load alleviation was achieved up to reduced frequencies of k=0.192.

scholarly journals An investigation of unsteady 3D effects on trailing edge flaps

2016 ◽  
Vol 753 ◽  
pp. 022009 ◽  
Author(s):  
E Jost ◽  
A Fischer ◽  
T Lutz ◽  
E Krämer
Keyword(s):  
Trailing Edge ◽  
Trailing Edge Flaps ◽  
3D Effects
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