Unsteady Design Optimization for Aeroelasticity Applications

Aeroelasticity plays an important role in the design and development of highly flexible flight vehicles and blended wing body configurations. The operating margins on these flight systems are limited by non-linear unsteady phenomena such as stall, flutter, gusts, limit cycle oscillations, vortex roll-up which exhibit strong coupling between the aero-loads and structural deformations. The use of high-fidelity time domain methods such as CFD/FEM during the design phase has been limited by the cost of computing the unsteady physics. In this proposal researchers from CRAFT Tech and Georgia Tech offer a collaborative inter-disciplinary design optimization approach to aeroelasticity problems with high fidelity aerodynamics analysis and structural dynamics. This approach is primarily feasible because of the development of a novel unsteady analysis procedure that reconstructs the unsteady dynamics with high accuracy and nominal cost. The reconstruction procedure combines CFD and FEM with a modified Proper Orthogonal Decomposition method and an Artificial Neural Network to simulate the unsteady aeroelastic features associated with different shape designs with good reliability. Furthermore, the process of reconstructing the unsteady solution permits the incorporation of control strategies and time variant system responses making it appealing for the aeroservoelasticity class of problems.

The design tools developed have wide applicability at NASA. The primary focus of the proposal is related to the design of flexible wing configurations used in HALE class of flight vehicles. However, the technology can have a significant impact on NASA's fixed wing program in guiding design of ultra-high bypass ratio engines and open rotor propeller systems from an aeroelasticity perspective. The smaller blades that are used in the ultra-high bypass ratio engines have very different aeroelastic characteristics and threshold criteria for fatigue and structural failure from traditional engines. The modern open rotor propeller systems are designed as a twin rotor configuration where there is significant interaction between the forward and aft rotors making the blades susceptible to flutter. Lastly, boundary layer flow distortion in BWB configurations can result in large dynamic pressures on fan blades in the embedded engines resulting in the increased risk of flutter.

One of the biggest beneficiaries of this technology would be the wind energy industry. Wind turbine blades are susceptible to aeroelastic effects and the problems are compounded in wind farms and sites close to the ocean where wind gusts are prevalent. The rotorcraft industry directly benefits from this technology as it can be used in the design of rotor blades where retreating blade stall is a big concern. Other commercial applications include gas turbine technology, commercial pump companies and the aerospace industry.

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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