Aerothermoelasticity has become a hot research area for several years around the world. Professor YANG Chao and his group from Beihang University set out to tackle this problem. Their work, entitled "A high-efficiency aerothermoelastic analysis method", was published in Sci China-Phys Mech Astron, 2014, 57(6): 1111-1118.

A hypersonic aircraft generally refers to a hypersonic flight vehicle whose flight Mach number is greater than 5.0 and which can fly in the atmosphere and across the atmosphere. Because of its outstanding performance, aerodynamic heating would clearly affect the structural stiffness, which would result in more complex aerothermoelastic problems, and therefore, it is necessary to develop an aerodynamic-heat-structure coupling analysis method for hypersonic flight vehicles.

The initial and rigid aerodynamic force has been widely used in a type of aerodynamic-heat-structure coupling analysis, called one-way coupling form, in several previous studies, where the effect of elastic deformation on the aerodynamic force is ignored.

Two-way coupling form involves the structural elastic deformation varying with flight time, and the effect of deformation on the aerodynamic force and aerodynamic heating is considered in the analysis process, and therefore, this method is characterized by good analytical precision

In most two-way coupling analyses, aerodynamic heating is computed using Eckert's reference temperature method due to its good precision and fast running speed, where thermal conduction is based on Fourier's law. The structure is analyzed using the finite element method (FEM), which is commonly used in engineering. The aerodynamic heating is analyzed based on aerodynamic forces.

Unified hypersonic lifting surface theory can consider both the effects of thickness and upwash by making the best use of both piston theory and classical lifting surface theory, and the method is less affected by the Mach number.

Compared with the CFD method, this method is suitable for hypersonic two-way coupling static aeroelasticity analysis due to its similar precision and rapid calculation speed, and aerodynamic models can be changed rapidly. However, thus far, this aerodynamic analysis method has not been applied to a two-way coupling aerothermoelastic analysis.

Combining the aforementioned key technologies, this paper proposes a hypersonic elastic analysis method framework, as shown in figure 1. The main processes and methods are as follows: first, based on the two-way coupling form, the hypersonic aerodynamic forces are solved using unified hypersonic lifting surface theory, and then the aerodynamic heat is calculated by the Eckert reference temperature method.

Then, the thermal structure is analyzed by the FEM using the modal method for elastic correction. Finally, the p-k method is used to calculate the flutter speed. A low-aspect ratio wing, as shown in figure 2, is taken as the analysis model in this paper.

With increase in flight time, aerodynamic heating will cause serious heat cumulative effects that can decrease the structural stiffness and flutter speed. The flight trajectory parameters, particularly the combined action of the flight state and flight time, must be given full consideration to meet the design requirements of hypersonic aircraft.

Wan Z Q, Wang Y K, Liu Y Z, Yang Chao. A high-efficiency aerothermoelastic analysis method. Sci China-Phys Mech Astron, 2014, 57(6): 1111-1118