Multidisciplinary dynamics modeling and analysis of a generic hypersonic vehicle

Fluid-thermal-propulsive-structural coupling exists during the design of generic hypersonic vehicles. A two-dimensional air-breathing generic hypersonic flight vehicle model has been developed according to the design concept of hypersonic vehicle's integrated airframe/scramjet configuration, and aerodynamic model is derived from oblique-shock/Prandtl-Meyer theory and momentum theorem. A free beam model of variant cross-section and mass distribution is introduced as the structure of the vehicle, and the approach of Eckert's reference enthalpy is used to obtain temperature distribution as a function of time along the axial direction of the beam, above which the assumed modes method is used to obtain the natural frequencies and mode shapes of the structure during the consumption of fuel and aerodynamic heating. Flight dynamics equations coupled with aerothermoelasticity are finally presented. The results indicate that the structural characteristic is dominated by the mass variation over the aerodynamic heating, the effect of which is enhanced as the aerodynamic heating progresses. Results also indicate that trimmed states are changed by the effect of the flexible deflection especially at the beginning of flight process, and the aerodynamic heating enhances the effect of flexible deflection. The dynamic eigenvalues of linearized system show that both structural deflection and mass decrease adversely increase the instability of the short period and phugoid modes, while the altitude mode is slightly affected. Moreover, aerodynamic heating enhances the coupling between flight dynamics and aeroelasticity and decreases the stability of flexible modes.