Experimental Study on the Use of Synthetic Jet Actuators for Lift Control

Experimental Study on the Use of Synthetic Jet Actuators for Lift Control
Author:
Publisher:
Total Pages: 94
Release: 2014
Genre: Dissertations, Academic
ISBN:

An experimental study on the use of synthetic jet actuators for lift control is conducted. The synthetic jet actuator is placed on the pressure side towards the trailing edge on a NACA 65(2)-415 airfoil representative of the cross section of an Inlet Guide Vane (IGV) in an industrial gas compressor. By redirecting or vectoring the shear layer at the trailing edge, the synthetic jet actuator increases lift and decreases drag on the airfoil without a mechanical device or flap. A compressor map that defines upper and lower bounds on operating velocities and airfoil dimensions, is compared with operating conditions of the low-speed wind tunnel at San Diego State University, to match gas compressor conditions in the wind tunnel. Realistic test conditions can range from Mach=0.12 to Mach= 0.27 and an airfoil chord from c=0.1 m to c=0.3 m. Based on the operating conditions, a final airfoil model is fabricated with a chord of c=0.1m. Several synthetic jet actuator designs are considered. A initial synthetic jet is designed to house a piezoelectric element with a material frequency of 1200 hz in a cavity with a volume of 4.47 cm33 a slot width of 0.25 mm, and a slot depth of 1.5 mm. With these dimensions, the Helmholtz frequency of the design is 1800Hz. Particle Image Velocimetry (PIV) experiments show that the design has a jet with a peak centerline jet velocity of 26 m/s at 750 Hz. A modified slant face synthetic jet is designed so that the cavity fits flush within the NACA airfoil surface. The slanted synthetic jet has a cavity volume of 4.67 cm3, a slot width of 0.25 mm, and a slot depth of 3.45 mm resulting in a Helmholtz frequency of 1170 hz for this design. PIV experiments show that the jet is redirected along the slant face according to the Coanda effect. A final synthetic jet actuator is directly integrated into the trailing edge of an airfoil with a cavity volume of 4.6 cm3, a slot width of 0.2 mm, and a slot depth of 1.6 mm. The Helmholtz frequency is 1450 Hz and matches closely with the piezoelectric element material frequency. The slot is designed so that actuator creates a jet normal to the airfoil surface. A wind tunnel model of the airfoil is 3D-printed with nine actuators integrated along the span of the airfoil. The synthetic jet slots cover 61% of the airfoil's span and the synthetic jet slots are located at a 13% chord upstream of the trailing edge. Tests are performed at multiple free stream velocities ranging from 17 m/s to 54 m/s which is the equivalent of an airfoil Reynolds number of Re=1:5_105 to Re=4:5_105. The integrated synthetic jet actuator increases lift. The increase is dependent on the freestream velocity, the actuation frequency, and angle of attack. For actuation at 1450 hz, and various freestream velocities, the synthetic jet actuator increases the lift by 2% at [lower case alpha]=7° to 7% at[lower case alpha] =15° . The synthetic jet increases L/D by 2% at[lower case alpha]=7° to 15% at [lower case alpha]=15° . Velocity contours obtained through PIV show that the synthetic jet turns the trailing edge shear layer similar to a Gurney flap, which increases lift. The synthetic jet reduces the wake velocity defect through injection of momentum, reducing the drag on the airfoil.

An Experimental Study of Synthetic Jet Actuators with Application in Airfoil LCO Control

An Experimental Study of Synthetic Jet Actuators with Application in Airfoil LCO Control
Author: Sanjay Krishnappa
Publisher:
Total Pages: 194
Release: 2016
Genre: Actuators
ISBN:

An experimental study on the development and implementation of Synthetic Jet Actuators (SJAs) is conducted for eliminating aeroelastic phenomenon such as Limit Cycle Oscillations (LCO). One of the biggest challenges involved in the design of UAVs operating in unsteady atmosphere conditions is the susceptibility of the airframe to aeroelastic instabilities, such as flutter or LCO. Suppression of such instabilities can be achieved through the implementation of Active Flow Control (AFC) techniques, however to this day, a limited amount of experimental studies exist. Thus, the focus of this work is to develop a new AFC method consisting of an actuator that is directly instrumented in the internal volume of the airfoil. Due to the complex geometry of airfoil/actuator integration, advanced manufacturing technique has been employed for rapid manufacturing of these complex parts. In addition, a newly designed experimental test facility is fabricated to study the effect of the developed actuator on aerodynamic performance. Parametric analysis are conducted to investigate the effect of actuator along the airfoil surface, Reynolds number, and angle of attack. Results of this study demonstrated the actuator effectiveness on overall aerodynamic performance and show consistent trends with high-order Computational Fluid Dynamics (CFD).

Flow Control Techniques and Applications

Flow Control Techniques and Applications
Author: Jinjun Wang
Publisher: Cambridge University Press
Total Pages: 293
Release: 2019
Genre: Science
ISBN: 1107161568

Master the theory, applications and control mechanisms of flow control techniques.

Experimental Investigation of Active Wingtip Vortex Control Using Synthetic Jet Actuators

Experimental Investigation of Active Wingtip Vortex Control Using Synthetic Jet Actuators
Author: Peter J. Sudak
Publisher:
Total Pages: 124
Release: 2014
Genre: Actuators
ISBN:

An experiment was performed in the Cal Poly Mechanical Engineering 2x2 ft wind tunnel to quantify the effect of spanwise synthetic jet actuation (SJA) on the drag of a NACA 0015 semispan wing. The wing, which was designed and manufactured for this experiment, has an aspect ratio of 4.20, a span of 0.427 m (16.813”), and is built around an internal array of piezoelectric actuators, which work in series to create a synthetic jet that emanates from the wingtip in the spanwise direction. Direct lift and drag measurements were taken at a Reynolds Number of 100,000 and 200,000 using a load cell/slider mechanism to quantify the effect of actuation on the lift and drag. It was found that the piezoelectric disks used in the synthetic jet actuators cause structural vibrations that have a significant effect on the aerodynamics of the NACA 0015 model. The experiment was performed in a way as to isolate the effect of vibration from the effect of the synthetic jet on the lift and drag. Lift and drag data was supported with pressure readings from 60 pressure ports distributed in rows along the span of the wing. Oil droplet flow visualization was also performed to understand the effect of SJA near the wingtip.

Flow Control Via Synthetic Jet Actuation

Flow Control Via Synthetic Jet Actuation
Author: Adam Cole Miller
Publisher:
Total Pages:
Release: 2005
Genre:
ISBN:

An experimental investigation was undertaken to determine the ability of Synthetic Jet Actuators to control the aerodynamic properties of a wing. The Synthetic Jet Actuator (SJA) was placed at two separate positions on a wing comprised of a NACA0015 airfoil. The first of the jet positions is located at 12% of the chord, hereby referred to as the leading edge Synthetic Jet Actuator. The second exit position is located at 99% chord of an airfoil and hereby is referred to as the trailing edge Synthetic Jet Actuator. The two locations produced different benefits as the angle of attack of the wing was increased. The leading edge Synthetic Jet Actuator delayed the onset of stall of an airfoil, suppressing stall up to 25 degrees angle of attack. The control of the aerodynamic characteristics was achieved by influencing the amount of the separated flowfield region. The effects of the dynamic stall vortex were investigated with wind tunnel testing during the pitching motion of an airfoil to determine how the flow reacts dynamically. The trailing edge synthetic jet actuator was investigated as a form of low angle "hingeless" control. The study investigated the effect of the jet momentum coefficient on the ability of the synthetic jet to modify the lifting and pitching moment produced from the wind tunnel model. The data indicates that, with the present implementation, the SJA-jet flap generates moderate lift and moment coefficient increments that should be suitable for hinge- less control. It was also shown that, for the current experimental setup and a given jet momentum coefficient, continuous blowing is more effective than oscillatory blowing/sucking. The data shows that combining the SJA with a Gurney flap does not result in performance enhancement.

Synthetic Jet Actuation - Modeling, Actuator Development and Application to Separation Control

Synthetic Jet Actuation - Modeling, Actuator Development and Application to Separation Control
Author:
Publisher:
Total Pages: 141
Release: 2004
Genre:
ISBN:

This work presents an investigation of synthetic jet actuation for separation control over wings/airfoils, in steady and unsteady flows, the development of high-power, compact synthetic jet actuators (SJA) for flow separation control, the modeling and control of such actuators and the modeling and control of the resulting SJA-controlled aerodynamics and wing/airfoil, respectively. The developed actuator is compact enough to fit in the interior of a NACAOOl5 profiled wing with a chord of 0.375 m. Test bench experiments showed that the multi-piston actuator array was capable of producing exit velocities of up to 90 rn/s for an actuator frequency of 130 Hz. The actuator was placed in a NACA 0015 wing and tested in a wind tunnel. An experimental investigation into the effects of a synthetic jet actuator on the performance of the wing, in steady flow, is described. Emphasis is placed on the capabilities of the actuator to control the separation of the flow over the wing at high angles of attack. The investigation included the use of force balance measurements, on -surface flow visualization with oil and tufts, off-surface flow visualizations with smoke, surface pressure distribution measurements and wake surveys.

Computational Study of a NACA4415 Airfoil Using Synthetic Jet Control

Computational Study of a NACA4415 Airfoil Using Synthetic Jet Control
Author: Omar Dario Lopez Mejia
Publisher:
Total Pages: 384
Release: 2009
Genre:
ISBN:

Synthetic jet actuators for flow control applications have been an active topic of experimental research since the 90's. Numerical simulations have become an important complement of that experimental work, providing detailed information of the dynamics of the controlled flow. This study is part of the AVOCET (Adaptive VOrticity Control Enabled flighT) project and is intended to provide computational support for the design and evaluation of closed-loop flow control with synthetic jet actuators for small scale Unmanned Aerial Vehicles (UAVs). The main objective is to analyze active flow control of a NACA4415 airfoil with tangential synthetic jets via computational modeling. A hybrid Reynolds-Averaged Navier-Stokes/Large Eddy Simulation (RANS/LES) turbulent model (called Delayed Detached-Eddy Simulation-DDES) was implemented in CDP, a kinetic energy conserving Computational Fluid Dynamics (CFD) code. CDP is a parallel unstructured grid incompressible flow solver, developed at the Center for Integrated Turbulence Simulations (CITS) at Stanford University. Two models of synthetic jet actuators have been developed and validated. The first is a detailed model in which the flow in and out of the actuator cavity is modeled. A second less costly model (RSSJ) was also developed in which the Reynolds stress produced by the actuator is modeled, based on information from the detailed model. Several static validation test cases at different angle of attack with modified NACA 4415 and Dragon Eye airfoils were performed. Numerical results show the effects of the actuators on the vortical structure of the flow, as well as on the aerodynamic properties. The main effect of the actuation on the time averaged vorticity field is a bending of the separation shear layer from the actuator toward the airfoil surface, resulting in changes in the aerodynamic properties. Full actuation of the suction side actuator reduces the pitching moment and increases the lift force, while the pressure side actuator increases the pitching moment and reduces the lift force. These observations are in agreement with experimental results. The effectiveness of the actuator is measured by the change in the aerodynamic properties of the airfoil in particular the lift ([Delta]C[subscript t]) and moment ([Delta]C[subscript m]) coefficients. Computational results for the actuator effectiveness show very good agreement with the experimental values (over the range of -2° to 10°). While the actuation modifies the global pressure distribution, the most pronounced effects are near the trailing edge in which a spike in the pressure coefficient (C[subscript p]) is observed. The local reduction of C[subscript p], for both the suction side and pressure side actuators, at x/c = 0.96 (the position of the actuators) is about 0.9 with respect to the unactuated case. This local reduction of the pressure is associated with the trapped vorticity and flow acceleration close to the trailing edge. The RSSJ model is designed to capture the synthetic jet time averaged behavior so that the high actuation frequencies are eliminated. This allows the time step to be increased by a factor of 5. This ad hoc model is also tested in dynamic simulations, in which its capacity to capture the detail model average performance was demonstrated. Finally, the RSSJ model was extended to a different airfoil profile (Dragon Eye) with good results.

Modeling of Synthetic Jet Actuators for Active Flow Control

Modeling of Synthetic Jet Actuators for Active Flow Control
Author: Rahul Sekhri
Publisher:
Total Pages: 240
Release: 2005
Genre: Actuators
ISBN:

Synthetic jet actuators (SJAs) are one of the newly developed actuators that have demonstrated great potentials in active flow applications, particularly in closed-loop flow controls. The SJA contains a piezoelectric membrane in a cavity, which vibrates and generates a periodic jet at the exit of the cavity through an orifice that is mounted flush with the solid wall of the flow field. In order to design the feedback control laws, it is crucial to be able to quantitatively capture the dynamics of SJAs. In this thesis, the dynamics of SJAs with six different orifice sizes are experimentally investigated. A synthesis using system identification for the purpose of constructing mathematical models of these zero mass-flux actuators is offered. The experimental study includes two output parameters, the acoustic sound pressure generated by the SJA and the mechanical membrane vibration of the SJA. State-space models for these outputs (sound pressure and mechanical vibration) are developed as a function of orifice size. These results form a foundation for future intelligent design of SJAs. A preliminary result of flow-velocity measurement is given, and finally the contributions of this entire work and future recommendations are discussed as part of the conclusions.