To improve the efficiency of the aerodynamic shape optimization based on the discrete adjoint method in a wide speed range, a hybrid time integration method is proposed. The hybrid method consists of the lower-upper symmetric Gauss-Seidel (LU-SGS) scheme, approximate Newton-Krylov (ANK) scheme, and Newton-Krylov (NK) scheme. The LU-SGS scheme is first employed to start the iteration, and then the ANK and NK schemes are sequentially used to accelerate the convergence rate. The relative convergence of the residual norm is employed to switch the three methods above. The ANK method is selected until the residual norm decreases by 2–4 orders of magnitude. The NK method is specified when the residual norm is 10² to 10³ times the target residual. By this switching strategy, the hybrid scheme is able to accelerate the convergence rate and improve the efficiency of aerodynamic optimization. The results of the test cases demonstrate that the solver employing the LU-SGS+ANK+NK scheme is 75% faster than that using the LU-SGS scheme. Moreover, compared to the Runge-Kutta (RK)+ANK+NK and diagonalized diagonally dominant alternating direction implicit (D3ADI)+ANK+NK schemes, the LU-SGS+ANK+NK scheme exhibits greater robustness. Furthermore, in a wide-speed-range aerodynamic optimization case, the optimizer based on the hybrid integration scheme is about 70% faster than that based on the LU-SGS method by accelerating each flow field simulation.

To address the multidisciplinary coupling problem faced by the air-breathing hypersonic airframe/propulsion integrated design, a two-layer multidisciplinary optimization design method is proposed based on flight mission requirementsand considers aerodynamics, trajectory, and control. Firstly, an optimization method for the geometric parameters is established using sequential quadratic programming to optimize the flight performance such as flight rangeand duration, with controllability as the constraint. Then, by solving the Reynolds Average Navier-Stokes (RANS) equations, the aerodynamic characteristics of the selected shape is obtained. With the obtained aerodynamic data, a mapping model from geometric parameters to aerodynamic characteristics is constructed. Subsequently, based on the existing dynamic data, a thrust model of the scramjet engine considering the influence of forebody parametersand nozzle parameters is established. After that, an internal trajectory optimization method is proposed. This method maintains the same optimization objectiveand constrain as geometric parameter optimization, and adopts the direct shooting method for discreteand the SQP algorithm for optimization. In addition, a control simulation model is constructed based on, which was combined with the to establish an aerodynamic, trajectoryand control integrated design method inner trajectory optimizationand outer parameter optimization are combinedand the Active Disturbance Rejection Control (ADRC) technology is used evaluate trajectory controllability, achieving two-layer multidisciplinary optimization for airframe/propulsion integrated design. Finally, optimization of the shape parametersand aircraft trajectory of the SR-72-like hypersonic vehicle are carried out to achieve the optimal range. The optimization results show that the maximum range is increased by 28.98% during the whole flight mission, demonstrating the effectiveness of the proposed method.

The hypersonic inward-turning inlet has attracted wide attention because of its higher compression efficiencyand larger flow coefficient. Nowadays, traditional design methods cannot achieve the optimal performance of the inlet. Therefore, coupling the genetic algorithmand the gradient algorithm, this paper proposes a new design method for the hypersonic inward-turning inlet based on the hybrid optimization strategy, and completes the design of the inlet at Mach number 6. Firstly, the global configuration design of the basic flowfield is conducted using genetic optimization, resulting in a Pareto front of basic flowfields with good performance. Among them, a typical dual-shock wave basic flowfield is selected to design the dual-shock wave inward-turning inlet. Secondly, the refined shape design of the above inlet is carried out based on adjoint gradient optimization, which further improves the performance of the inlet. Consequently, compared to inward-turning inlets designed using the traditional forward design methods, the performance of the inlet constructed by the design method is significantly improved. The flow coefficient, total pressure recovery coefficientand pressure rising ratio are increased by 2.33%, 13.15%and 7.90%, respectively, and the distortion coefficient (DC₆₀) is reduced by 3.70%. During the global configuration design, the overall parameters of the basic flowfield, such as the radius of the center bodyand outlet, are designed to obtain the optimal-performing global configuration of basic flowfield. During the refined shape design, the fluctuations of the inlet surface improve the mass capture performanceand compression capability of the shock wave in the isolation section. In addition, the surface deformation also weakens the total pressure loss caused by the second incident shock wave, the development of streamwise vortexesand the flow separation induced by shock-wave/turbulent-layer interaction in the isolation section. Furthermore, the weakening of streamwise vortexesand flow separation results in the reduction of total pressure loss in the isolation sectionand the improvement of flow uniformity on the outflow boundary.

The integrated configuration of the waverider forebody and inward turning inlet is one of the mainstream choices for the long-range hypersonic cruise vehicle due to its great high-speed lift-drag characteristics, superior inflow capture ability and high compression efficiency. To improve the performance of the integrated configuration, this paper proposes an integrated design method based on improving the basic flowfield design and considering the viscous effect. In terms of basic flowfield design improvement, the total pressure distribution of the reflected shock wave is improved to a quadratic distribution which can reduce the gradient of the total pressure distribution. After giving the antitangent Mach number distribution on the upper wall and the Bezier flow angle distribution on the center body wall, the high-total-pressure-recovery internal compression basic flowfield with the controllable flow field distribution in the whole flow channel is designed. Compared with the local inverse design basic flowfield with only a given Mach number distribution on the upper wall, the central body of the new basic flowfield becomes a tapered surface, the intensity of the reflected shock wave is greatly reduced, and the total pressure recovery coefficient is greater than 0.98. The resulting integrated configuration maintains the characteristics of the basic flowfield while exhibiting lower strength of the reflected shock wave in the inner contraction section and the shock wave train in the isolation section and the reduced proportion of the low energy region at the exit. Consequently, the lift-to-drag ratio at the design point increase by 15.16%, the total pressure recovery coefficient at exit increase by 3.33%, and the distortion at exit decrease by 4.62%. In terms of the consideration of the viscous effect, this paper combines the high-fidelity numerical solution results with the displacement thickness calculation formula of the axisymmetric boundary layer to carry out the viscosity correction. Compared with the traditional two-dimensional plate boundary layer viscosity correction method, the axisymmetric configuration verification example shows that the proposed method can improve the profile correction accuracy and reduce the deviation from the inviscid design performance target. This method is applied to the viscosity correction of the original configuration to obtain a modified configuration. Compared with the original configuration, the closure of the forebody shock wave and the incident shock wave at the lower lip of the modified configuration is improved, the strength of the reflected shock wave in the internal contraction section and the shock wave train in the isolation section is decreased, and the separation area of the internal flow channel caused by the boundary layer interference of the shock wave is reduced. The flow coefficient at the design point is increased by 3.22%, and the total pressure recovery coefficients of the throat and exit at the design point are increased by 2.41% and 0.31%, respectively. Moreover, the aerodynamic performances at the lift-weight balance point and in the wide-speed range are also significantly improved. In summary, the integrated design of waverider forebody / inward turning inlet proposed in this paper offers better lift-drag and flow-capture performance, providing valuable insight for the aerodynamic design of the longrange hypersonic cruise vehicle.