Title page for ETD etd-10192005-113327
|Type of Document
||Efficient and robust design optimization of transonic airfoils
|Grossman, Bernard M.
|Haftka, Raphael T.
|Mook, Dean T.
|Schetz, Joseph A.
|Walters, Robert W.
- Transonic Research.
- Air flow Research
|Date of Defense
Numerical optimization procedures have been employed for the design of airfoils
in transonic flow based on the transonic small-disturbance (TSD) and Euler
equations. A sequential approximation optimization technique was implemented for
solving the design problem of lift maximization with wave drag and area constraints.
A simple linear approximation was utilized for the approximation of the lift. Accurate
approximations for sensitivity derivatives of the wave drag were obtained
through the utilization of Nixon's coordinate straining approach. A modification
of the Euler surface boundary conditions was implemented in order to efficiently
compute design sensitivities without recreating the grid. Our design procedures
experienced convergence problems for some TSD solutions, where the wave drag
was found not to vary smoothly with the design parameters and consequently create
local optimum problems. A procedure interchanging the role of the objective
function and constraint, initially minimizing drag with a constraint on the lift was
found to be effective in producing converged designs, usually in approximately 10
global iterations. This procedure was also shown to be robust and efficient for cases
where the drag varied smoothly, such as with the Euler solutions. The direct lift
maximization with move limits which were fixed absolute values rather than fractions
of the design variables, was also found to be a reliable and efficient procedure
for designs based upon the Euler equations.
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