###### Abstract
The research results show that the calculation program used in the article tends to underestimate the total pressure recovery at the engine inlet section and overestimate the distortion level [6]. In order to accurately predict the performance of aircraft inlet under extreme flight conditions, [PERSON] et al. used numerical simulation methods to explore the inlet. The results showed that the calculated results were in good agreement with the surface static pressure of the precursor in the wind tunnel test results, and the calculated results were slightly lower than the experimental data. This difference may be partly due to the low mesh resolution at the inlet lip [7]. [PERSON] and others developed a maneuvering inlet test device based on dual torque motor synchronous drive, simulated the rapid pitching and other maneuvering processes of the fighter and different working conditions of the inlet, and established the unsteady test method of the fighter inlet. The basic law of inlet performance change during a fast pitch maneuver of a fighter model is studied by means of the test [8]. [PERSON] conducted a wind tunnel test study on the dynamic characteristics of the bump inlet on both sides and explored the aerodynamic characteristics of the inlet within a certain angle of attack. The research results show that the total pressure recovery coefficient and distortion index have a strong unsteady hysteresis effect, which is significantly different from the steady-state results at the same angle of attack [9]. [PERSON] et al. applied the dynamic nested mesh technology to study the dynamic aerodynamic characteristics of the fighter's inlet under a rapid pitch maneuver and verified it with flight data. They captured the unsteady hysteresis effect in the inlet during the fighter's maneuver flight and analyzed its influencing factors and mechanism [10; 11; 12; 13]. However, most of the current research on the unsteady flow characteristics in the inlet during maneuvering flight is carried out for the conventional inlet with a windward surface, and it is difficult to find the relevant information of the submerged inlet in the domestic and foreign open literature. The design of the submerged inlet integrated with the aircraft body has many advantages. In addition to significantly reducing the windward surface of the aircraft and reducing the wind resistance, it can also reduce the radar scattering area and improve the survivability of the aircraft [14; 15; 16; 17]. At present, the submerged inlet is widely used in cruise missiles and UAVs, such as the cruise missile AGM-129 and the whaling fork of the United States [18; 19]. Researchers from various countries have also carried out a series of research on the submerged inlet. As early as 1945, [PERSON] et al. designed a NACA submerged inlet and carried out a lot of experiments on it. The submerged inlet uses a long inclined plate with a very small angle of inclination (about \(7^{\circ}\)) to introduce air into the inlet, but the intake volume of the inlet is small and the total pressure recovery coefficient is low [20; 21; 22; 23; 24; 25]. Subsequently, a large number of researchers carried out in-depth research on the intake mechanism [26; 27], optimization design method [28; 29; 30], internal flow characteristics [31; 32; 33], and flow control method [34; 35; 36; 37] of the submerged inlet. Now the performance of the submerged inlet can basically meet the engineering application requirements. However, the research on the submerged inlet is only limited to the steady numerical simulation or ground wind tunnel experiment when the angle of attack and sideslip of the aircraft are constant. The research on the unsteady flow characteristics of the submerged inlet in the process of large maneuvering flight is still blank, and the research on the optimization and flow control method of the submerged inlet in the process of large maneuvering flight is impossible.