# 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
The positive value of the relative variation rate of _Cps_ represents the relative increase of the plane area averaged static pressure rise coefficient, while the positive values of the relative variation rate of \(\omega_{s}\) and \(\delta s\) represent the relative decrease of the plane mass averaged total pressure loss coefficient and the plane area averaged blockage coefficient, respectively. The corresponding body force of each single plasma actuator shown in Figure 9 is confined to 837 mN/m. According to Figure 9a, the influences of the suction surface plasma actuation on the high-speed compressor cascade static pressure rise coefficient vary slightly with the change of incidence angles. Figure 9: Influences of plasma actuations on the high-speed compressor cascade total pressure loss, static pressure rise, and blockage coefficients at different incidences. (**a**) Suction surface plasma actuation; (**b**) Endwall plasma actuation. It can be found the static pressure rise coefficient of the high-speed compressor cascade achieves a relative increase of 3% with the suction surface plasma actuation. However, the incidence angle imposes a remarkable influence on the control effects of the suction surface plasma actuation in reducing the high-speed compressor cascade total pressure loss and blockage coefficients. At an incidence angle of 1\({}^{\circ}\), the total pressure loss coefficient of the high-speed compressor cascade achieves a maximum relative reduction of 10.1% with the suction surface plasma actuation. With the increase of incidence angles, strength of the high-speed compressor cascade corner separation is enhanced, and the ability of the suction surface plasma actuation to reduce the corresponding total pressure loss thus decreases. The scope of the influence of plasma actuation is limited to the regions near solid walls, and this leads to the inefficiency of the suction surface plasma actuation in reducing the total pressure loss of large-scale high-speed compressor cascade corner separations at large positive incidence angles. With the decrease of incidence angles, the strength of the high-speed compressor cascade corner separation is weakened, and the pressure side separation contributes more and more to the overall total pressure loss of the high-speed compressor cascade flow. As a result, the ability of the suction surface plasma actuation to reduce the total pressure loss at negative incidence angles decreases too. At an incidence angle of 0\({}^{\circ}\), the blockage coefficient of the high-speed compressor cascade achieves a maximum relative reduction of 2.3% with the suction surface plasma actuation. With the change of incidence angles, the variance of the influences of the suction surface plasma actuation on the high-speed compressor cascade blockage coefficient obeys a similar rule to its influences on the high-speed compressor cascade total pressure loss coefficient discussed above. According to Figure 9b, compared to the work conditions of large positive incidence angles, the endwall plasma actuation imposes stronger influences on the high-speed compressor cascade static pressure rise coefficients at negative and small positive incidence angles. At an incidence angle of 1\({}^{\circ}\), the static pressure rise coefficient of the high-speed compressor cascade achieves a maximum relative increase of 4.2% with the endwall plasma actuation. At an incidence angle of 7\({}^{\circ}\), the total pressure loss coefficient achieves a maximum relative reduction of 5.7% with the endwall plasma actuation. 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 total pressure loss coefficient and the endwall plasma actuation both decrease. However, the endwall plasma actuation imposes stronger influences on the high-speed compressor cascade total pressure loss coefficient at large positive incidence angles than at small positive and negative incidence angles.