scholarly journals Active Flow Control Methods for the Reduction of Trailing Edge Noise

2017 ◽  
Author(s):  
Máté Szoke ◽  
Mahdi Azarpeyvand
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Control Methods ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Active Flow

Trailing edge noise reduction of wind turbine blades by active flow control

Wind Energy ◽  
2014 ◽  
Vol 18 (5) ◽  
pp. 909-923 ◽  
Author(s):  
Alexander Wolf ◽  
Thorsten Lutz ◽  
Werner Würz ◽  
Ewald Krämer ◽  
Oksana Stalnov ◽  
...  
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Noise Reduction ◽  
Active Flow Control ◽  
Turbine Blades ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Active Flow

Closed-Loop Active Flow Control of the Wake of a Compressor Blade by Trailing-Edge Blowing

2015 ◽  
Author(s):  
Matthias Kiesner ◽  
Rudibert King
Keyword(s):  
Flow Control ◽  
Mass Flow ◽  
Closed Loop ◽  
Active Flow Control ◽  
Hammerstein Model ◽  
Robust Controller ◽  
Trailing Edge ◽  
Velocity Deficit ◽  
Reference Velocity ◽  
Active Flow

This paper presents a closed-loop active flow control strategy to reduce the velocity deficit of the wake of a compressor stator blade. The unsteady stator-rotor interaction, caused by the incoming stator wakes, generates fast changes of the rotor blade loading, affecting the stability and the performance of the overall compressor. Negative effects will be seen likewise when unsteady combustion concepts, such as a pulsed detonation, produce upstream disturbances. Furthermore, the periodic unsteady flow leads to additional undesired effects such as noise and blade vibrations. A controlled reliable manipulation of the stator wake is a way to handle these issues. Therefore, investigations on wake manipulation with trailing-edge blowing were carried out on a new low-speed cascade test rig. Detailed information about the wake profile is obtained by five-hole probe measurements in a plane downstream of the cascade for the natural and the actuated flow at a Reynolds number of 6×105. These measurements show a significant reduction of the wake velocity deficit for the investigated actuator geometry with an injection mass flow of less than 1% of the passage mass flow. Based on these results a position in the wake was chosen which is representative for the actuation impact on the velocity deficit. There, a hot-wire-probe measurement serves as the controlled variable. A family of linear dynamic black-box models was identified from experimental data to account for nonlinear and unmodelled effects. Static nonlinearitiy was compensated for by a Hammerstein model to reduce the model uncertainty and get a higher controller performance. To handle off-design conditions, a robust controller working in a range of Reynolds numbers from 5×105 to 7×105 was synthesized. The task of the controller is to rapidly regulate the controlled variable to a reference velocity by changing the blowing amplitude. The synthesized robust controller was successfully tested in closed-loop experiments with good results in reference tracking for pulse series up to 20 Hz. This translates into a much higher frequency when scaled to the dimension of a real machine.

Towards Active Flow Control on a Research Scale Wind Turbine Using PID controlled Trailing Edge Flaps

2018 ◽  
Author(s):  
Sirko Bartholomay ◽  
Grigoris Michos ◽  
Sebastian Perez-Becker ◽  
George Pechlivanoglou ◽  
Christian Nayeri ◽  
...  
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Active Flow Control ◽  
Trailing Edge ◽  
Trailing Edge Flaps ◽  
Active Flow

Dynamic Aeroelastic Response of Wind Turbine Rotors Under Active Flow Control

2019 ◽  
Author(s):  
Muraleekrishnan Menon ◽  
Fernando L. Ponta
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Active Flow Control ◽  
Load Control ◽  
Aerodynamic Load ◽  
Trailing Edge ◽  
Trailing Edge Flaps ◽  
Utility Scale ◽  
Active Flow

Abstract The significance of wind power and the associated relevance of utility-scale wind turbines are becoming more prominent in tapping renewable sources for power. Operational wind turbines today rated at 8 MW have rotor diameters of 164 m. Economies-of-scale factor suggest a sustained growth in rotor size, forecasting the use of longer and heavier blades. This has led to an increased emphasis on studies related to improvements and innovations in aerodynamic load-control methodologies. Among several approaches to controlling the stochastic aerodynamics loads on wind turbine rotors, most popular is the pitch control. Widely used in operational wind turbines, conventional pitch control is an effective approach for long-term load variations. However, their application to mitigate short-term fluctuations have limitations that present a bottleneck for growth in rotor size. Sporadic changes occurring within short time scales near the turbine rotor have significant impact on the aeroelastic behavior of the blades, power generation, with long-term effects on the rotor life-span. Cyclic variations occurring within few seconds emphasize the need for swift response of control methods that counter the resulting adverse effects. Current study revolves around the need to evaluate innovative active load control techniques that can swiftly handle high frequency oscillations in dynamic loading of turbine rotors. This may result from sudden changes in wind conditions due to gusts, environmental effects like atmospheric boundary layer and uneven terrain, or from turbine design features and operating conditions such as tower shadow effects. The upward surge in rotor size is linked with a down-side for existing techniques in rotor control that now need to account for heavier blades and the associated inertia. For example, the pitching operation rotates the entire blade around its longitudinal axis to regulate angle of wind at specific blade sections, involving huge inertial loads associated with the entire blade. On the other hand, active flow-control devices (FCDs) have the potential to alleviate load variations through rapid aerodynamic trimming. Trailing-edge flaps are light weight attachments on blades that have gradually gained relevance in studies focused on wind turbine aerodynamics and active load control. This computational study presents an aeroelastic assessment of a benchmark wind turbine based on the NREL 5-MW Reference Wind Turbine (RWT), with added trailing-edge flaps for rapid load control. The standard blades used on the NREL 5-MW RWT rotor are aerodynamically modified to equip them with actively controllable fractional-chord trailing-edge flaps, along a selected span. The numerical code used in the study handles the complex multi-physics dynamics of a wind turbine based on a self-adaptive ODE algorithm that integrates the dynamics of the control system in to the coupled response of aerodynamics and structural deformations of the rotor. Using the 5-MW RWT as a reference, the blades are modified to add trailing-edge flaps with Clark Y profile and constant chord. Attached at chosen sections of the blade, these devices have a specific range of operational actuation angles. Numerical experiments cover scenarios relevant to the aeroelastic response of a rotor with such adapted blades under operating conditions observed in utility-scale wind turbines. These fractional-chord devices attached along short spans of the blades make them light weight devices that can be easily controlled using low power of actuation. This overcomes the bottleneck in active aerodynamic load control, giving flexibility to study a wider ranged of control strategies for utility-scale wind turbines of the future. Preliminary outcomes suggest that rapid active flow control has high potential in shaping the future of aerodynamic load control in wind turbines.

Active Flow Control for Reduction of Fluctuating Aerodynamic Forces of a Blunt Trailing Edge Airfoil

2009 ◽  
Author(s):  
Arash Naghib Lahouti ◽  
Horia Hangan
Keyword(s):  
Flow Control ◽  
Numerical Simulations ◽  
Control Mechanism ◽  
Active Flow Control ◽  
Three Dimensional ◽  
Leading Edge ◽  
Aerodynamic Forces ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
Active Flow

Vortex shedding from the base of two dimensional bluff bodies is accompanied by three dimensional wake instabilities. These instabilities manifest as streamwise and vertical vorticity components which occur at a certain spanwise wavelength. The spanwise wavelength of the instabilities (λz) depends on several parameters, including profile geometry and Reynolds number. The present study aims to determine λz for a blunt trailing edge airfoil, which is comprised of an elliptical leading edge, followed by a rectangular section. Results of numerical simulations of flow around the airfoil at Re(d) = 500, 800, 1200, and 17,000, and flow visualization at Re(d) = 2200 indicate that λz has an average value of 2.2d. An active flow control mechanism based on the three dimensional wake instabilities is proposed, to attenuate the fluctuating aerodynamic forces of the airfoil. The mechanism is comprised of trailing edge injection ports distributed across the span, with a spacing equal to λz. Injection of a secondary flow leads to excitation of the three dimensional instabilities and disorganization of the von Ka´rma´n vortex street. Numerical simulations at Re(d) = 500 and 17,000 indicate that the flow control mechanism can attenuate the fluctuating aerodynamic forces significantly, and reduce mean drag using a relatively small injection mass flow rate.

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