During high-speed flight, the significant coupling effect between high dynamic pressure and aerodynamic heating-induced thermal gradients causes substantial cumulative aerothermoelastic deformation, which critically impacts flight performance and safety. Currently, cumulative thermal deformation is typically predicted using multi-physics coupling methods; however, research regarding the influence of the coupling time step, a critical parameter in such analyses, remains relatively scarce. To address this gap, the present study employs a fully numerical aerodynamic-thermal-structural two-way coupling method developed by our research team. Taking a two-dimensional flat plate structure as the research object, we systematically investigate the influence of coupling time step on cumulative thermal deformation predictions under various angles of attack and Mach numbers. The results demonstrate that the coupling time step primarily affects the peak value and the long-time heated steady-state value of the cumulative thermal deformation history: larger time steps lead to greater peak deformation but smaller steady-state deformation. Compared to variations in angle of attack, Mach number exerts a more pronounced influence on time step sensitivity, with higher Mach numbers requiring smaller coupling time steps. When focusing on fine-scale evolution, the time step is set to < 2 s; to balance efficiency and accuracy, a time step of 2 s is adopted (with a maximum deformation deviation of < 12% and a steady-state deviation of < 6%); if only steady-state values are of interest, a time step of 5 s can be used, improving computational efficiency by a factor of about 10. Excessively large time steps may induce non-physical oscillations, necessitating reasonable step size constraints to balance computational efficiency and accuracy. Based on systematic analysis of the relative deformation deviation as a function of coupling time step, Mach number, and angle of attack, a selection strategy for coupling time steps is proposed. These findings provide valuable guidance for efficient and refined prediction of cumulative thermal deformation in long-endurance high-speed flight vehicles.

Next-generation large-scale lightweight aircraft experience more significant cumulative thermal deformation during prolonged high-speed flight than conventional aircraft, adversely affecting flight performance. Focusing on typical high-aspect-ratio cavity plate structures, this study adopted a high-fidelity fully numerical aero-thermal-structural coupled analysis method to investigate: (1) structural deformation evolution under coupled aerodynamic heating and loading, (2) thermal-mechanical interaction mechanisms, and (3) deformation effects on flight performance. The results showed that under prolonged severe heating conditions, the thermal deformation of cavity structures was determined by the combined effects of time-accumulated thermal factors and instantaneous mechanical loads, exhibiting three distinct evolutionary stages: Stage I (rapid deformation dominated by cold-wall heating), Stage Ⅱ (gradual deformation increase followed by recession under continued aerodynamic heating), and Stage Ⅲ (stabilized deformation through thermal-mechanical equilibrium). Unlike solid structures, cavity structures demonstrated this unique recession behavior consistently across different Mach numbers and angles of attack. The cumulative thermal deformation caused nonlinear variations in aerodynamic characteristics throughout the flight, leading to adverse effects such as deviations in lift-to-drag ratios and pitching moments. These findings highlight the need to address such thermal deformation effects in the design of future high-speed aircraft.

Due to prolonged and repeated flights at high Mach numbers, aircraft geometric layout deformation is induced by the accumulated comprehensive force/thermal effects. In this study, the cumulative thermal deformation effect of the fuselage is treated as an uncertainty input. Uncertainty quantification and modeling are conducted and integrated into the aerodynamic layout optimization process. A robust optimization model for high-speed aircraft has been developed in this paper, along with a proposed solution strategy. Four distinct optimization models were solved, compared, and analyzed, thereby verifying the robustness of the model and the efficacy of the solution approach. Simulation results indicate that the accuracy of aerodynamic predictions is significantly influenced by the cumulative thermal deformation effect. Consequently, the propagation of predictive deviation can disrupt the optimization convergence direction, thereby impacting the final optimal configuration.

Geometry parametrization plays a significant role in Aerodynamic Shape Optimization (ASO). A succinct, accurate, and efficient geometric presentation method can effectively improve the optimization efficiency and the design results. Principal Component Analysis (PCA) is a common way to extract data features and reduce data dimension. In this paper, an airfoil geometry parameterization method based on the PCA is firstly introduced. Then, the influences of sampling space, sample number, sampling method and geometric reconstruction method on PCA dimension reduction ability, base mode characteristics and geometric presentation ability are analyzed. Furthermore, the presentation ability of the PCA method on aerodynamic characteristics is also studied based on computation fluid dynamics. Simulation results show that: the PCA method could effectively describe the airfoil geometry shape with preferable accuracy and relatively few, physically meaningful parameters; based on a specific sampling method, the PCA mode, the dimension reduction ability and the geometric accuracy are little affected by the sampling space and the sample number, though they are sensitive to the parameters of the sampling method; the PCA method described in this paper could not only accurately describe the geometry shape, but also ensure the accuracy of the aerodynamic forces to a certain degree, which has certain guiding significance in ASO applications.