Aerothermoelastic Reduced-Order Model of a Hypersonic Vehicle

Abstract

Model reduction techniques are applied to a hypersonic vehicle on terminal trajectories to capture the aerodynamic, thermodynamic, and structural dynamic system evolution and couplings. The General Pseudospectral Optimization Software (GPOPS-II) was used to determine a set of terminal trajectories which maximized impact velocity. Shock, Prandtl-Meyer expansion, and piston theory were combined to create an approximate flow solution over the outer mold line which was then compared to Fully Unstructured Navier-Stokes 3-Dimensional (FUN3D) computational fluid dynamics solutions. Proper orthogonal decomposition of the thermal state of the vehicle was conducted leading to 33 thermal degrees of freedom rather than approximately 28,000 contained by a representative finite element model, while sacrificing negligible system energy. Free vibration mode shapes are derived and used to generalize the structural dynamics equations of motion reducing the number of structural degrees of freedom to 8 from the original 130,000. Finally, the combination of these reduced order models is discussed in the context of future work toward a full vehicle simulation.

Nonlinear Thermal Reduced-Order Modeling for Hypersonic Vehicles

“…To compare each ROM approach, a sample FEM was established that was representative of a small portion of the hypersonic vehicle proposed by Pasiliao et al [14] and later refined by Witeof and Neergaard [15]. This substructure was located at the interface of the vehicle nose ballast and forebody, on the Earth-facing side during typical flight conditions, in a region that was previously shown in [25] to experience high thermal loads and contain several different materials. For simplicity, this substructure was considered to be approximately two-dimensional, despite the curvature of the vehicle's body in this region.…”

“…The flight trajectory consisted of a 520 s, Mach 6, 75 kft (22.9 km) altitude cruise phase, during which the vehicle was trimmed for propelled steady and level flight, followed by a 37.5 s unpropelled terminal phase along a path optimized for maximum final kinetic energy. Details of this trajectory and optimization process may be found in [25]. Once the flow properties near a node of interest were found, the Eckert reference temperature [10] and black-body radiation methods were used to determine the heat flux _ q w to the node.…”

Multi-Discipline Modeling of Complete Hypersonic Vehicles Using CFD Surrogates

“…All free flying vehicle responses are evaluated using the University of Michigan High-Speed Vehicle (UM/HSV) code, which provides a framework for aerodynamic, thermodynamic, and elastic interaction simulation of hypersonic vehicles using full and reduced order models. [22][23][24] The code includes six degree of freedom flight time simulation, high speed vehicle trim, and linear state matrix identification. A more detailed description of the aeroelastic solution methods is described by Klock and Cesnik.…”

“…A more detailed description of the aeroelastic solution methods is described by Klock and Cesnik. [22][23][24] The code is written in a modular format that allows for the removal, exchange, or isolation of entire components. This enables trade studies for models of varying fidelity.…”

Aeroelastic Stability of High-Speed Cylindrical Vehicles

“…Recent work by the authors [1][2][3][4][5] has been on the development of a set of reduced order models (ROMs) used in the University of Michigan High-Speed Vehicle (UM/HSV) aerothermoelastic simulation framework. These models have focused on the Initial Concept 3.X (IC3X) vehicle 6 designed by Witeof and Neergaard using the Preliminary Aerothermal Structural Simulation code suite.…”