## 3 Results and Discussion
### Study on Flow Control of Vertical Tail under Different Momentum Coefficients
The pressure coefficient curves of the upper wing surface of the vertical tail are more \"full\", which is reflected in the force measurement results of the aerodynamic force obtained by the surface pressure integration. The pressure coefficient curve of Figure 13b is consistent with the results of [PERSON]'s [25] research. It proves that the pressure tap arrangement in this paper is reasonable and reduces the collection of unnecessary data. That is, the lateral force of the vertical tail increases. The measured pressure data are consistent with the measured force results, which show that the oscillating jet flow control can slow down or even eliminate the flow separation on the upper surface of the rudder, thereby increasing the vertical tail lateral force. According to the aerodynamic measurement results, when the vertical tail sideslip angle is \(0^{\circ}\) and the rudder deflection angle is \(15^{\circ}\), the control effect of the oscillating jet is obvious, and the lateral force increment under the control of different momentum coefficients is different. Therefore, we have studied the space flow field distribution in the vertical tail controlled by the momentum coefficients of various actuators under this condition. Figure 12: Lateral force coefficient and increment of vertical tail model under different momentum coefficient controls: (**a**) lateral force coefficient curves; (**b**) lateral force coefficient increment curves (\(\beta=0^{\circ}\), \(Re=2.12\times 10^{5}\)). Figure 13: Rudder pressure distribution under different momentum coefficient controls: (**a**) \(\delta=5^{\circ}\); (b) \(\delta=25^{\circ}\) (\(\beta=0^{\circ}\), \(Re=2.12\times 10^{5}\)). Figure 14 shows that \(\beta=0^{\circ}\), \(\delta=15^{\circ}\), and \(Re=2.12\times 10^{5}\), with the spatial flow field distribution of the vertical tail model under different momentum coefficient controls. When no flow control is applied, flow separation occurs on the vertical tail rudder from the trailing edge, and the streamline is far away from the rudder. When the momentum coefficient of the oscillating jet is 0.083%, the separation area on the rudder decreases, the streamline begins to come close to the rudder surface, and there is a noticeable flow acceleration area on the stabilizer in front of the hinge. When the momentum coefficient of the oscillating jet is increased to 0.166%, the separation area on the rudder and the flow acceleration area on the stabilizer do not change significantly, and the exit velocity of the former momentum coefficient actuator is slightly increased. When the momentum coefficient of oscillating jet continues to increase to 0.332%, the streamline comes in close to the rudder, and the velocity diagram and streamline diagram change little from the previous momentum coefficient. In general, as the jet's momentum coefficient increases, the flow velocity on the stabilizer varies little in the range of 0.98 to 1.02. The application of the exciter has little effect on the upstream flow and the dimensionless mainstream velocity at the hinge increases from 1.01 to 1.12. The effect of the exciter is evident here and downstream.