Defense Dissertation: Aerodynamic Shape Optimization with Time-Spectral Flutter Adjoint

Sicheng He Aerospace Engineering PhD Candidate

Virtual- Zoom (Please register before hand)
https://umich.zoom.us/meeting/register/tJcudOuurT4vG9y33TQA1IDLv10GbWMd8yaJ

Flutter and limit cycle oscillation (LCO) are important phenomena
that need to be considered in aircraft design. To avoid them in flight
envelope, we can conduct a multidisciplinary design optimization
(MDO) to maximize the flutter speed by changing the wing aerodynamic shape.

One challenge is that we need to simulate flutter or LCO efficiently
using high fidelity computational fluid dynamics (CFD) model in the
transonic regime. We propose a coupled Newton-Krylov method to
solve the time-spectral aeroelastic equations. We observe that the
proposed method is more efficient than the time-accurate method.

Another challenge is that we need to compute the flutter speed derivative with respect to a large number of design variables. We propose the use of coupled adjoint to address that. Using this adjoint solver, we conduct an aerodynamic shape optimization of a wing and the flutter speed increases by 118%.

Finally, for mode based aerostructural optimization problems, we identify a computational bottleneck related with the structural mode and natural frequency derivative computation. We propose two formulae based on reverse algorithmic differentiation to reduce the cost from number of design variables computations to a single computation.

Defense Committee Members:
Prof. Joaquim R. R. A. Martins (Chair)
Prof. Bogdan Epureanu (Cognate)
Prof. Carlos E. S. Cesnik (Member)
Assoc.Prof. Krzysttof Fidkowski (Member)