Extensive tests were carried out on a section of a wind turbine blade. The effect of reduced frequency on the boundary layer transition point of the model oscillating in plunge has been investigated. The spatial-temporal progressions of the transition point and the state of the unsteady boundary layer were measured using multiple hot-film sensors. The measurements showed that reduced frequency highly affects variations of the transition point and results in a hysteresis loop in the dynamic transition locations. The dominated frequencies of the boundary layer are found to be a function of the reduced frequency and mean angle of attack.

Numerous experiments have been conducted on plunging Eppler 361 AIRFOIL in a subsonic wind tunnel. The experimental tests involved measuring the surface pressure distribution over the AIRFOIL at Re=1.5×105. The AIRFOIL was equipped with Gurney flap(heights of 2.6, 3.3 and 5% chord) and plunged at 6cm amplitude. The unsteady aerodynamic loads were calculated from the surface pressure measurements, 51 ports, along with the chord on both upper and lower surfaces of the model. The Gurney flap effects over the loads hysteresis loops of the oscillating AIRFOIL were particularly studied prior to stall, at the stall onset, in light stall, and deep stall conditions. The static results of the flapped and unflapped AIRFOIL were also explored in order to make a reference of comparisonsto the dynamic loads. The results showed that, the addition of the Gurney flap provided no changes in the directions of the Cl, Cd and Cm hysteresis loops for the prior to stall flow conditions, while as a result of the positive camber effects, the lift hysteresis loops shifted upward and the pitching moment’s loops moved vertically downward. Additionally, adding the Gurney flap promoted dynamic stall phenomena.The deep dynamic stall of the flapped AIRFOIL with the height of h/c=5% was seen at ads=13.1deg. This phenomenon was observed at ads=14.8deg for the flapped AIRFOILs of h/c=2.6 and 3.3%.

Aerodynamic behavior of an AIRFOIL with circle, right and inverse triangle shaped damage was numerically investigated. The flow through the damage was driven by the pressure differential between the upper and lower wing surfaces. For all damage shapes, the results showed that the flow could be categorized as weak or strong jets. The jet exited the rear of the damage; its size was determined by the width of the rear part of the hole and was dependent on the shape of the damage. Generally, when compared with an undamaged model, increasing the angle of attack for a damaged model resulted in increased loss of lift coefficient, increased drag coefficient and more negative pitching moment coefficient. This effect was more severe for the right triangle case. Furthermore, the numerical results were compared with experimental data to study the effiect of a wall on the flow field.

The effects of a Trapped Vortex Cavity (TVC) on the aerodynamic performance of a NACA 0024 AIRFOIL at a constant angle of attack (AoA) of 14◦ were investigated in this study. It was observed that mass suction (MFR) was required to stabilise the vortex within the cavity segment. Lift to drag ratio (L/D) and MFR were chosen as performance objectives, along with a fully attached flow constraint (flow separation at X/c ≥ 95% ). Parametric analysis was carried on the baseline AIRFOIL with and without suction and compared to the AIRFOIL with TVC with and without suction. It was observed that L/D increases as MFR increases for a baseline AIRFOIL, and flow separation is delayed at high suction values (MFR = 0. 2 kg/s). The TVC modifies the pressure distribution on the baseline AIRFOIL when MFR is applied to the cavity section and there is a significant increase in lift, thus, L/D increases and flow separation is delayed. A lower value of MFR = 0. 08 kg/s is sufficient to stabilise the vortex and improve the efficiency of the TVC AIRFOIL. The findings of these parametric studies were used to do a multi-objective optimisation using a genetic algorithm to attain the desired cavity shape while achieving the largest L/D and the lowest MFR (that is proportional to the power required for control) with a fully attached flow constraint. It was found that mass suction and cavity shape both had an equal influence on flow control. The Pareto optimal front yielded a series of optimum designs. One of them was subjected to an off-design analysis in order to validate its performance at other incidences. It was observed that it performs better than the baseline AIRFOIL, with an improved L/D and an increase in stall angle from 10◦ to 14◦.

Nowadays the application of plasma actuators has drawn much attention due to the possibility of creating a volumetric force and, therefore, controlling airflow around rigid bodies. These actuators are among common flow control methods because of availability, lack of need for special repairs, very short response time, and low power consumption. The aim of this study is to reduce the flow separation region and delay the stall angle. Therefore, the airflow over a NACA 0012 AIRFOIL and with a Reynolds number of 1. 4×106 was simulated using Spalart-Allmaras turbulence model. In the first step, the lift coefficients in the plasma-off mode were investigated at different angles. The stall angle of attack was shown to be 15°, . Then, the lift coefficients and the stall angle for different Reynolds numbers were compared. In the second step, the plasma (DBD) actuator was defined using UDF code in Ansys Fluent software as the body force exerted on the AIRFOIL. Plasma activation led to an increase in the lift coefficients at different angles compared to the plasma-off mode. Subsequently, it was shown that the plasma actuator minimizes the flow separation area on the AIRFOIL. Defining this actuator at an optimal position at a constant RE of 1. 4×106 on a NACA 0012 AIRFOIL where flow separation occurs changed the stall angle of the AIRFOIL from 15°,under normal conditions to 19°, . The results of the lift coefficient with the help of plasma actuators showed that the airflow on the AIRFOIL is well controlled at sensitive attack angles.