Date of Award

Spring 2010

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Aerospace Engineering

Committee Director

Oktay Baysal

Committee Member

Drew Landman

Committee Member

Abdurrahman Hacioglu

Call Number for Print

Special Collections; LD4331.E535 I28 2010

Abstract

High-lift systems are frequently used on commercial transport aircrafts to obtain low speed performance, in terms of take-off and landing field lengths and approach speed. To maximize the take-off and landing performance within the critical restrictions required by the new generation transport wing designs, enhanced high-lift technologies are needed. Moreover, the economic realities faced by the airlines require a design that is mechanically simple and effective. These facts lead us to the optimization of the high lift systems.

Optimizing a high-lift system improves an aircraft's take-off and landing performance. The weight of the system, the advantages and the disadvantages all need to be taken into consideration accurately because of the economic realities and the critical restrictions on the new generation transport wing designs. To ensure the effectiveness of the system, researchers perform computational and experimental studies. The design optimization allows changing the position of an element of a high-lift system in a judicious manner, then the resulting lift coefficient, and overall performance are computed.

In this thesis, the flow around a multi-element airfoil is modeled using computational fluid dynamics, and the optimum position of the flap is obtained by an optimization method. The geometry of the multi-element airfoil MDA 30P-30N is imported into a grid generation software and the domain is discretized using multi-block, structural meshes. A Reynolds-Averaged-Navier-Stokes (RANS) flow solver is used to perform the computations resulting in the accurate simulation of the flow field. The present computed results are then successfully compared with a published experimental study of the same configuration. For the design optimization the slat of the airfoil is fixed with a deflection angle of 30o and the position of the flap is changed with two degrees of freedom, which are the overhang and vertical displacement.

A genetic algorithm is used for the present optimization process. The obtained optimal design is also compared with one published previously. This previous study, used herein for comparison, had utilized a steepest ascent-descent method on experimentally obtained flow parameters. The present computational design obtained with the genetic algorithm, compared very well with the experimental design obtained with the steepest descent method.

Some observations made during this are as follows: The overall effort, time and cost of the present approach is significantly more economical then the compared experimental study. Although multi-block grids used here provided more accurate solutions, they required more computational time to solve the flow as compared to the overlapped grids. Using a genetic algorithm in conjunction with computational fluid dynamics is a very efficient and effective approach. This is attributed to its global search characteristics which yield an optimal design in just a few generations.

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DOI

10.25777/xpkd-w473

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