# Control of Corner Separation with Plasma Actuation in a High-Speed Compressor Cascade
## 3 Results
### Performances of Plasma Actuations in Suppressing the High-Speed Compressor Cascade Flow Separation
In practice, at large positive incidence angles, the corner separation contributes the most to the total pressure loss of the high-speed compressor cascade, while, at small positive and negative incidence angles, the airfoil loss of pressure and suction side separations will play a more important role in producing the total pressure loss of the high-speed compressor cascade. Compared to the suction surface plasma actuation, the endwall plasma actuation is much more efficient in reducing the total pressure loss of corner separations and less efficient in reducing the total pressure loss of airfoil separations. At an incidence angle of 0\({}^{\circ}\), the blockage coefficient of the high-speed compressor cascade achieves a maximum relative reduction of 9.4%. Then, similar to the case of the suction surface plasma actuation, with the increase and decrease of incidence angles, the reduction of the high-speed compressor cascade blockage coefficient and the endwall plasma actuation both decrease. From Figure 9a,b, it can be found that the suction surface plasma actuation is more efficient in reducing the total pressure loss coefficient of the high-speed compressor cascade, while the endwall plasma actuation is more efficient in reducing the blockage coefficient and increasing the static pressure rise coefficient of the high-speed compressor cascade. These phenomena are associated with the mechanisms behind the control effects of plasma actuation in suppressing the high-speed compressor cascade flow separation, which will be discussed later. Influences of Body Force on the Control Effects of Plasma Actuation in Suppressing High-Speed Compressor Cascade Corner Separation  
Figure 10 shows the influences of plasma actuations on the high-speed compressor cascade total pressure loss and blockage coefficients, with plasma actuators inducing different body forces. The inlet flow incidence angle of the high-speed compressor cascade is confined to 0\({}^{\circ}\) in Figure 10.  
According to Figure 10a, with the increase of the body forces of plasma actuators, the relative reduction rate of the high-speed compressor cascade total pressure loss coefficient with the suction surface plasma actuation increases linearly, while the corresponding relative reduction rate of the high-speed compressor cascade blockage coefficient increases more and more slowly. According to Figure 10b, with the increase of the body forces of plasma actuators, the relative reduction rate of the high-speed compressor cascade total pressure loss and blockage coefficients with the endwall plasma actuation both increase linearly. Based on Figure 10a, it can be found that the control effects of plasma actuation in suppressing high-speed compressor cascade corner separation are not always linearly correlated with the body forces of plasma actuators. Two factors are responsible for this phenomenon. First, the scope of the influence of the suction surface plasma actuation is limited to the region near solid walls and cannot be directly enlarged with the increase of the body forces of plasma actuators. On the other hand, the corner separation is highly three-dimensional and always extends far away from the solid walls. As a result, when the body forces of the plasma actuators are increased, the ability of the suction surface plasma actuation to reduce the high-speed compressor cascade corner separation blockage is limited. Mechanisms behind the Control Effects of Plasma Actuations in Suppressing High-Speed Compressor Cascade Corner Separation  
Figure 11 shows the influences of plasma actuations on the total pressure at plane p6 and on the corresponding main flow structures. In Figure 11b,c, the variance of total pressure is obtained through the subtraction of the total pressure of baseline condition and from the plasma actuations, and the positive value in the figure indicates that plasma actuation improves the flow total pressure.