Session: 02-02-01: Aero-, Servo-, Thermo-Elastic Modeling and Optimization of Aerial Vehicles

Paper Number: 121670

121670 - Modal Design Optimization for Panel Flutter and Thermal Buckling 

Panel flutter is a long-studied phenomenon critical to aircraft design in which the thin exterior panels of the aircraft---having been subjected to aerodynamic pressure and heating---tend to lose elastic stability and either statically buckle or dynamically flutter. Critical to the phenomena of panel flutter is the design of the panels themselves. The nature of design is to minimize weight while providing sufficient strength to withstand both buckling due to heating and flutter due to flow over the panel. In this work, mass minimization is done via an optimization of panel thickness distribution with a flat external (flow-side) surface and variable-thickness internal (no-flow) surface as opposed to the fill-void techniques or adding discrete stiffeners.

The objective of this paper is to demonstrate a weight-optimized panel for thermal buckling and high-speed flutter stability. For this purpose, a computationally efficient model is developed from the Galerkin modal expansion of the Von Karman plate equations, including a nonlinear stretching term as the geometric nonlinearity. The aerodynamic forces are modeled with piston theory, and the thermal model is a temperature gradient between the plate and its boundary conditions, which in turn affects the model stiffness.

It should be noted that this work is the first phase of a larger design project, with the overarching objective of demonstrating multi-fidelity design optimization practices by considering a range of fidelities: from low-fidelity modal structures with piston theoretic aerodynamics presented here, to finite-element structures coupled with computational fluid dynamics aerodynamics, to experimental wind tunnel methods.

Therefore, the main objectives of this ongoing work are the following: 1) Demonstrate the utility of low-fidelity modal modeling techniques for optimization practices; 2) Demonstrate a panel which is mass-optimized for a) aerothermal loading, constrained so no buckling nor flutter occurs; b) aerothermal loading, constrained so a statically stabled buckled shape may occur while remaining flutter-free; c) aerodynamic loading only, constrained so no flutter occurs. For each case, the optimization is conducted using the lower fidelity tools and the solution is validated with commercial finite element solver ABAQUS. 

Presenting Author: Kevin McHugh Air Force Research Laboratory

Presenting Author Biography: Dr. McHugh studies aerothermoelastic phenomena and their impacts on air vehicle design at the Air Force Research Lab, where he has been toiling away since graduating from Duke University in 2020. His interests include reduced order modeling, thermal buckling, flutter and nonlinear post-flutter limit cycle oscillations.