Initial Implementation of an Adjoint CFD Code for Aeroshell Shape Optimization
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Author(s)
Flaherty, Kevin W.
Advisor(s)
Braun, Robert D.
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Abstract
Application of computational fluid dynamics to the optimization of aeroshell shapes usually entails high
computational cost. Many converged solutions are required to generate gradients and optimize a shape with
respect to very few design variables. The benefits of high-fidelity aerodynamic analysis can be reaped early in
the design cycle with less computational cost if the traditional direct optimization problem is transformed to
an indirect optimization, using optimal control theory. The indirect gradient formulation decouples the
effects on the objective function of the design variables and the flow solution. Meaning, all derivatives used to
compute the gradient can be generated from a single converged flow solution. Involved in the computation of
the gradient is the solution of an adjoint system of PDEs. An incremental approach is developed for the
implementation of an adjoint equation solver. The phased approach begins using inexact and computationally
costly finite difference derivative calculations. Results are presented for a transonic airfoil and a supersonic
wedge to demonstrate that the finite difference gradient is reasonably accurate, providing a meaningful
validation as exact numerical derivatives are substituted later in the development cycle. Finally, a roadmap is
presented for future implementation of indirect optimization capability for the Euler/Navier-Stokes CFD
code, NASCART-GT.
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Date
2008-03-05
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Text
Resource Subtype
Masters Project
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