Aerofoil Optimisation via Automatic Differentiation of a MultigridCell-Vertex Euler Flow Solver
by
T. Evans
DERA - British Aerospace
Coauthors: Shaun A Forth (Cranfield University, RMCS Shrivenham)

We report preliminary results in the use of ADIFOR to determine aerodynamic sensitivities of a 2-D Airfoil with respect to geometrical variables. For the initial study, finite differences are used to generate mesh sensitivities to spline perturbations to the aerofoil. Meshes are produced with a hyperbolic technique. The flow field is calculated using the cell-vertex method of Hall which incorporates local time-stepping, mesh sequencing and multigrid. Results and timings are presented for the following approaches to obtaining sensitivities: 1) Finite-Differences with perturbed solutions initialised from free-stream 2) Finite-Differences with perturbed solutions initialised with the current solution. 3) Automatic Differentiation commencing from freestream conditions. 4) Automatic Differentiation commencing from the current solution.

The setting of convergence criteria is discussed and we show how suitable control of the ADIFOR code results in a more robust and sometimes more efficient algorithm than the finite-difference approach.

Further, attempts were made at a comparative study of AD and DD gradients in an optimisation on a NACA aerofoil, using the DERA CODAS method. The work is assessed with an eye to DERA's eventual aim, 3D viscous optimisation on wing-body configurations.

Date received: February 15, 2000

Copyright © 2000 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cads-82.