## 4 The Flow Characteristics of Two Inlet Configurations under High Maneuver Condition
### Analysis of Transient Flow Characteristics
#### 4.2.2 Flow Characteristics of Submerged Inlet with Rapid Yaw Maneuver  
Let the mesh in the internal rotating region perform a simple yaw maneuver around the z-axis at two angular velocities, and the calculated total pressure recovery coefficient of the outlet of the inlet plane is shown in Figure 15.  
It can be seen from Figure 15 that in the range of \(\beta\) from \(-30^{\circ}\) to \(30^{\circ}\) during the yaw maneuver of the inlet of two configurations, the \(\sigma\) first increases, then decreases, then increases, and then decreases with the increase of \(\beta\), which is consistent with the trend of equivalent steady state calculation. When the absolute value of the \(\beta\) is less than \(20^{\circ}\), the transient and steady calculation results are almost consistent. When the \(\beta\) is close to \(\pm 30^{\circ}\), the transient calculation result is slightly higher than the steady calculation result.  
It can be seen from Figure 15a that the \(\sigma\) of the conventional submerged inlet drops sharply when the absolute value of \(\beta\) is greater than \(20^{\circ}\), and \(\sigma\) is less than \(0.65\) when the \(\beta=\pm 30^{\circ}\). \(\beta=0^{\circ}\) is considered as the equilibrium position. In the process of deviating from the equilibrium position, the \(\sigma\) is higher than that of approaching the equilibrium position. This phenomenon is particularly obvious in the range of \(\beta-30^{\circ}\) to \(-20^{\circ}\) and \(20^{\circ}\) to \(30^{\circ}\). This is due to the hysteresis effect of the flow field. Specifically, in the case of large sideslip flight, the side edge on the same side of the incoming flow can no longer produce entrainment vortices that are conducive to air intake, and the side edge on the opposite side of the incoming flow play a major role. In the process of deviating from the equilibrium position, the relative motion of the missile increases the angle between the airflow and the opposite side edge, thus increasing the intensity of the entrainment vortices, which is conducive to improving the intake efficiency. At the same time, it can be observed that the greater the angular velocity, the more obvious the hysteresis phenomenon.  
From Figure 15b, it can be seen that the distributed submerged inlet configuration also has a significant decrease when the absolute value of the \(\beta\) is greater than \(20^{\circ}\), but the decrease is smaller than that of the conventional submerged inlet configuration. When the absolute value of the \(\beta\) is \(30^{\circ}\), \(\sigma\) is still greater than \(0.8\). This is because the special structure of the distributed submerged inlet creates additional intake conditions, so that it is no longer overly dependent on the entrainment vortices generated by the side edge to drive the external airflow into the inlet. There is an obvious hysteresis phenomenon near the sideslip angle of \(12^{\circ}\). In the process of deviating from the equilibrium position, \(\sigma\) is higher than that near the equilibrium position. This is mainly because the auxiliary inlet on the opposite side of the incoming flow plays a major role in the large sideslip maneuver  
Figure 15: Total pressure recovery coefficient versus angle of sideslip. (**a**) Conventional submerged inlet, (**b**) Distributed submerged inlet.  
flight. In the process of deviating from the equilibrium position, the angle between the airflow and the inlet plane of the distributed inlet on the opposite side of the incoming flow is increased, which in turn increases the windward surface and leads to a higher total pressure recovery coefficient. At the same time, it can be observed that the greater the angular velocity, the more obvious the hysteresis phenomenon.