## 3 Results at Constant Angle of Attack  
Simulations with the blades at constant angle of attack are performed on the blade cascade, in order to investigate the affection of plasma actuation on mean loads and flow field. Only results on the central blade of the cascade are discussed in the following. The counterparts on the remaining blades are not reported for brevity purposes. The freestream velocity is 34.36 m/s and the angle of attack is two degrees. The Reynolds number is again \(\sim\)350,000. Figure 7 shows the time history of the airloads obtained with time-resolved simulations at fixed angle of attack. These simulations are meant to show that the flow can be assumed as steady in  
Figure 5: Distribution of pressure coefficient \(\rm C_{P}\). Experiments and CFD on the clean configuration; Re \(\sim\)350,000, \(\alpha=2\) degrees. Figure 6: Real and imaginary part of unsteady pressure distribution. Experiments and CFD on the clean configuration; Re \(\sim\)350,000; IBPA = 0 deg. ; \(\alpha=2+\sin\left(2\pi\mathrm{f}t+4\times\mathrm{IBPA}\frac{\pi}{180}\right)\) degrees; \(\mathrm{f}=5.25\) Hz; t: time. the mean, when the blades are kept at a constant angle of attack. The time step for the unsteady computations is set to \(1.6685\times 10^{-4}\) s and 100 time steps are performed for each period. It is found that all the three airloads converge to a constant value, after a maximum of \(\sim\)0.015 s. Therefore, steady state computations can be performed to assess the affection of plasma actuators on the force coefficients and on the flow field. Figure 8 shows the normalized velocity and vorticity magnitude fields. The velocity is made dimensionless by the freestream velocity and the vorticity is made dimensionless by the ratio of chord over freestream velocity. A detail of the trailing edge is displayed for the clean blade and for the configurations with PS and SS actuation, respectively. A body force of 300 mN/m is applied on the pressure and on the suction side. Both actuations lead to the development of low speed recirculating flow areas, with a consequent modification of local and resulting loads. In particular, PS actuation yields a recirculating flow region on the pressure side trailing edge, in the area where the plasma is modeled. These locally developed vortical structures shift the application point of the Kutta condition downstream of the physical trailing edge. This is approximately equivalent to employing a longer and more cambered airfoil. Therefore, lift augmentations are expected to be a direct consequence of this phenomenon. The recirculating flow area generated by SS actuation causes an induced camber effect that is opposite relative to the SS counterpart. As a consequence, the resulting effect will be a reduction in the developed airloads. The flow fields of Figure 8 show that, as expected, the wake becomes thicker relative to the clean blade counterpart--the light blue low speed region is larger for the actuated configurations. This effect, which is consistent with the results of Refs. [18; 19], may lead to possible drag increases compared to the baseline blade. Nevertheless, it will be hereinafter shown that no significant drag rises are encountered for both the actuated configurations. It is also worth noting that the recirculating flow area developed on the suction side is less extended, relative to the pressure side counterpart. This is probably due to the fact that higher velocity gradients are encountered on the suction side, near the trailing edge. Therefore, a larger body force is probably required on the suction side, in order to obtain almost equally extended recirculating flow areas on upper and on the lower side of the blade. It will be illustrated that a consistent asymmetry is encountered in terms of local and resulting airloads achieved with PS or SS actuation.