On Nov 16, 2010, at 5:11 AM, Matteo Lombardi wrote:
The gradient is obtained via the resolution of the direct and
Adjoint flow field and the evaluation of the "sensitivity" (i.e.
gradient) field.
I have checked it, the gradient is correct (at least qualitatively).
I would check the gradient quantitatively. Compare it to a brute-
force finite-difference approximation, and make sure it is accurate to
several decimal places.
It is really easy to get gradient computations wrong, and incorrect
gradients will often cause gradient-based methods to fail to converge.
Also make sure you are solving your CFD problem accurately; if you are
using some iterative method with a low tolerance for your solver, you
may have a lot of numerical noise in your objective, and gradient-
based methods are very intolerant of noise (or any other non-
smoothness) in the objective.
I don't see any other reason why gradient-based methods would on your
sort of problem.
Steven
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