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.

This project examined the effect of Gurney flaps on a 2D, 2-ft chord NACA 0036 airfoil in the Cal Poly 3’x4’ low speed wind tunnel at 25 m/s. It also covered the numerical simulation of the experiment in computational fluid dynamics (CFD). During the study, problems with the wind tunnel data were seen. After a careful diagnosis, the problem was traced to dirty flow conditioners which were subsequently replaced. Five Gurney flaps at 1, 2, 3, 4, and 5% of the chord were tested. The Gurney flaps had the effect of eliminating the lift reversal effect and lowering the profile drag at low angles of attack, ranging from 4-27%. The optimal Gurney flap appeared to be 2% of the chord. CFD modeling of the problem had limited success, with the best results coming from Mentor’s k-w SST turbulence model. This model reproduced the non-linear lift curve, and captured the trend in rising drag fairly well, but failed to predict the correct point of separation. Attempts to model the Gurney flap in CFD were unsuccessful.

Flow separation is a common fluid dynamics phenomenon that occurs within supersonic nozzles while operating at off-design pressures. Typically, off-design pressures result in a shock formation that leads to a non-uniformity of the exiting flow and creates flow separation and flow recirculation. So far, no effective solution has been presented to eliminate flow separation and increase the total performance of the nozzle. The purpose of this work is to investigate whether a Gurney flap may beneficially affect the exiting flow pattern. For a better understanding of the Gurney flap effect, this investigation used a supersonic nozzle geometry based on a previous study by Lechevalier [33]. Results from the tested cases showed a poor effect of the flap at high free-stream Mach number and lower pressure ratio. Simulations of different flap heights along with different parameters showed a slight increase of thrust.

With the advantage of modern high speed computers, there has been an increased interest in the use of first-principles based computational approaches for the aerodynamic modeling of horizontal axis wind turbine (HAWT). Since these approaches are based on the laws of conservation (mass, momentum, and energy), they can capture much of the physics in great detail. The ability to accurately predict the airloads and power output can greatly aid the designers in tailoring the aerodynamic and aeroelastic features of the configuration. First-principles based analyses are also valuable for developing active means (e.g., circulation control), and passive means (e.g., Gurney flaps) of reducing unsteady blade loads, mitigating stall, and for efficient capture of wind energy leading to more electrical power generation. In this present study, the aerodynamic performance of a wind turbine rotor equipped with circulation enhancement technology (trailing edge blowing or Gurney flaps) is investigated using a three-dimensional unsteady viscous flow analysis. The National Renewable Energy Laboratory (NREL) Phase VI horizontal axis wind turbine is chosen as the baseline configuration. Prior to its use in exploring these concepts, the flow solver is validated with the experimental data for the baseline case under yawed flow conditions. Results presented include radial distribution of normal and tangential forces, shaft torque, root flap moment, surface pressure distributions at selected radial locations, and power output. Results show that good agreement has been for a range of wind speeds and yaw angles, where the flow is attached. At high wind speeds, however, where the flow is fully separated, it was found that the fundamental assumptions behind this present methodology breaks down for the baseline turbulence model (Spalart-Allmaras model), giving less accurate results. With the implementation of advanced turbulence model, Spalart-Allmaras Detached Eddy Simulation (SA-DES), the accuracy of the results at high wind speeds are improved. Results of circulation enhancement concepts show that, at low wind speed (attached flow) conditions, a Coanda jet at the trailing edge of the rotor blade is effective at increasing circulation resulting in an increase of lift and the chordwise thrust force. This leads to an increased amount of net power generation compared to the baseline configuration for moderate blowing coefficients. The effects of jet slot height and pulsed jet are also investigated in this study. A passive Gurney flap was found to increase the bound circulation and produce increased power in a manner similar to the Coanda jet. At high wind speed where the flow is separated, both the Coanda jet and Gurney flap become ineffective. Results of leading edge blowing indicate that a leading edge blowing jet is found to be beneficial in increasing power generation at high wind speeds. The effect of Gurney flap angle is also studied. Gurney flap angle has significant influence in power generation. Higher power output is obtained at higher flap angles.

Helicopters are versatile vehicles that can vertically take off and land, hover, and perform maneuver at very low forward speeds. These characteristics make them unique for a number of civilian and military applications. However, the radial and azimuthal variation of dynamic pressure causes rotors to experience adverse phenomena such as transonic shocks and 3-D dynamic stall. Adverse interactions such as blade vortex interaction and rotor-airframe interaction may also occur. These phenomena contribute to noise and vibrations. Finally, in the event of an engine failure, rotorcraft tends to descend at high vertical velocities causing structural damage and loss of lives. A variety of techniques have been proposed for reducing the noise and vibrations. These techniques include on-board control (OBC) devices, individual blade control (IBC), and higher harmonic control (HHC). Addition of these devices adds to the weight, cost, and complexity of the rotor system, and reduces the reliability of operations. Simpler OBC concepts will greatly alleviate these drawbacks and enhance the operating envelope of vehicles. In this study, the use of Gurney flaps is explored as an OBC concept using a physics based approach. A three dimensional Navier-Stokes solver developed by the present investigator is coupled to an existing free wake model of the wake structure. The method is further enhanced for modeling of Blade-Vortex-Interactions (BVI). Loose coupling with an existing comprehensive structural dynamics analysis solver (DYMORE) is implemented for the purpose of rotor trim and modeling of aeroelastic effects. Results are presented for Gurney flaps as an OBC concept for improvements in autorotation, rotor vibration reduction, and BVI characteristics. As a representative rotor, the HART-II model rotor is used. It is found that the Gurney flap increases propulsive force in the driving region while the drag force is increased in the driven region. It is concluded that the deployable Gurney flap may improve autorotation characteristics if deployed only over the driving region. Although the net effect of the increased propulsive and drag force results in a faster descent rate when the trim state is maintained for identical thrust, it is found that permanently deployed Gurney flaps with fixed control settings may be useful in flare operations before landing by increasing thrust and lowering the descent rate. The potential of deployable Gurney flap is demonstrated for rotor vibration reduction. The 4P harmonic of the vertical vibratory load is reduced by 80% or more, while maintaining the trim state. The 4P and 8P harmonic loads are successfully suppressed simultaneously using individually controlled multi-segmented flaps. Finally, simulations aimed at BVI avoidance using deployable Gurney flaps are also presented.