Numerical investigation of fluid-thermal-structural interaction of deployable control fin in hypersonic flow

Abstract

In this paper, a nonlinear aerothermoelastic analysis of a deployable control fin subjected to Mach 7 hypersonic flow is presented. The fin consists of the inboard and outboard parts joined together with a revolute joint having freeplay nonlinearity. The fin is assumed to be a whole movable fin and, hence, is connected to an actuator having nonlinear stiffness characteristics. The fin is made of the annealed Ti-6Al-4V material, which has temperature-dependent physical, mechanical, and thermal properties. To perform a coupled fluid-thermal-structural interaction analysis, a delayed detached eddy simulation method-based fluid dynamics solver is strongly coupled to a finite element method-based thermoelastic solver in the time domain. The effects of fin aspect ratio, thickness ratio, free stream dynamic pressure, and structural damping on the flow field as well as structural dynamics characteristics are investigated and presented. Since the flow is highly compressible at Mach 7 and the temperature rise is observed to be sufficient to excite the vibrational modes of the diatomic nitrogen and oxygen of the atmosphere, the air is modeled as a calorically imperfect gas. Shock interactions and concentrated vortices originating from various high-thickness locations at the joint as well as root sections are observed. It is found that at high altitudes, the contribution of the torsional mode is significant in fin deformation, whereas, at low altitudes, the bending mode contribution is higher. Also, it is shown that the fin aspect ratio, thickness ratio, and damping ratio have significant effects on the fin stability and performance.