Doctoral Dissertations

Date of Award

12-1988

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Aerospace Engineering

Major Professor

Walter Frost

Committee Members

John Caruthers, T. H. Moulden, B. A. Kupershmidt, J. M. Wu

Abstract

A recent innovation in aerodynamic calculation techniques is a formulation for the velocity field based upon scalar and vector potentials. This technique is presented and implemented into the panel method such that it is able to solve not only irrotational flow but also rotational flow. The application of interest is to two-dimensional airfoils moving into a nonuniform approach flow. Comparisons with theoretical and numerical results are included. Furthermore, the variations of lift and moment coefficients of quasi-steady simulated flight of an airfoil through JAWS wind shear are also studied.

Although the present study does demonstrate the hazard of microbursts, the indicated wind shear effects on aerodynamic coefficients are not as great as ex pected. The present method only indicates the decrease of the effective angle of attack as an important factor. However, in a wind field with intense downdrafts, viscous effects and flow separation should also be crucial. Although the present inviscid model has shown great advantages as a preliminary study of the wind shear effects on aerodynamic coefficients, it cannot predict viscous effects and flow separation phenomena. Therefore, further investigation is recommended to implement viscous effects.

For potential flow calculations, comparable accuracy to that obtainable from higher-order panel methods can be achieved by the present formulation using the same number of control points. The present conceptual split of the onset flow into two components, V0n→ normal and V0n→ tangential to the zero lift line, is new. The proper vorticity distribution can be determined from -V0n→ ⋅ n→ directly without imposing an artificial vorticity distributor. This split also supplies a numerically superior form for the Neumann-type lower-order formulation.

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