Preliminary Aero-thermal Structural Simulation

2017

AIAA Journal

A set of reduced-order models are considered to determine the variation of the material thermal capacity and thermal conductivity with respect to temperature for a representative hypersonic vehicle structure on a terminal trajectory. The number of thermal degrees of freedom is first reduced by projecting the thermal state of a sample structure into a modal space whose bases are determined using proper orthogonal decomposition. A numerical integration scheme based on the Crank-Nicolson algorithm is used to simulate the thermal state forward in time. Models for the generalized material thermal properties are based on the method of kriging, a least-squares polynomial approximation, and a singular value decomposition approach. The resulting thermal models are compared in terms of accuracy and computational efficiency. The singular value decomposition approach is shown to be the superior overall reduced-order model to capture the variation of thermal properties with temperature when compared to a full-order finite element solution. The effects of varying the number of retained thermal modes and thermal property eigenvectors on the singular value decomposition model are then considered. It is shown that only a few eigenvectors need to be considered to achieve excellent agreement with finite element analysis.

Section: A Structural Modelmentioning

confidence: 99%

Section: E Comparison To Finite Element Analysismentioning

confidence: 99%

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Nonlinear Thermal Reduced-Order Modeling for Hypersonic Vehicles

2017

AIAA Journal

“…The second test case is a representative hypersonic vehicle configuration modified from the Initial Concept 3.X (IC3X) design established by Witeof and Neergaard 17 using the PASS code suite 18 and shown in Figure 3.…”

Section: Sample Hypersonic Vehiclementioning

confidence: 99%

Rapid Simulation of a Hypersonic Vehicle Through Singular Value Decomposition

58th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

2017

A reduced order model based on singular value decomposition and correlation is developed to capture the nonlinear dynamics of a hypersonic vehicle in flight. A set of training samples in state space form are collected using the complex step method. These samples are used to identify a set of ordered bases which describe the variation of the state matrices and state rates. Surrogate functions are fit to the coefficients of these bases to approximate the training samples and predict the state matrices outside of the training set. The dynamics of the system may then be rapidly simulated, provided the training set sufficiently populates the state space. This approach is first applied to a spring-mass-damper system with variable nonlinearity and number of degrees of freedom to determine training sample size and surrogate function orders which produce stable and accurate time simulation. A representative hypersonic vehicle is then considered to demonstrate the potential of this approach for rapid simulation of hypersonic flight.

“…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. 7 The IC3X is a rocket-boosted scramjet vehicle which cruises at Mach 5 and above and at an altitude of 50 thousand feet or higher before entering an unpowered terminal dive. Preliminary simulations of the IC3X in the high dynamic pressures of the thermal phase have shown the onset of body flutter similar to the flutter of cylindrical shells in supersonic flow.…”

Section: Introductionmentioning

confidence: 99%

Aeroelastic Stability of High-Speed Cylindrical Vehicles

58th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

2017

Different levels of structural modeling fidelity are evaluated against experimental results for the aeroelastic stability boundaries of an internally pressurized circular cylindrical shell. A modal approach is taken to model the structural dynamics while third-order piston theory is used to model the external and internal surfaces' unsteady aerodynamic pressures. Results are used to inform model improvements of freeflight aero-thermo-elastic simulation in order to accurately predict aeroelastic instabilities in a representative supersonic vehicle. The stability of a finite-element model when inclined to the flow is also considered in an unpressurized condition to inform future work where a cylindrical high-speed vehicle is required to perform maneuvers.