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Steady and nonsteady potential flow methods for airfoils with spoilers Brown, Geoffrey Phillip

Abstract

In part I a linearized cavity potential flow theory is developed to solve both the steady state airfoil spoiler problem and the transient loads on an airfoil during and after spoiler actuation. The theory is also applicable to the case of an airfoil with a spoiler and a flap. The theory uses conformal transformations to map that part of the airfoil exposed to the flow onto the upper half of a unit circle. The complete flow field about the airfoil maps into the upper half plane exterior to this unit circle. Although no limitations are imposed in the paper upon the spoiler height, angle, or location, good agreement with experiment would not be expected in such a linearized theory for very large spoilers. Spoiler heights up to 10% of the airfoil chord are considered, and the theory shows good agreement with experiment. A theory for the steady state airfoil spoiler problem for a solid airfoil, and an airfoil with a slotted flap is developed in part II. An exact potential free streamline theory using the surface singularity technique is used in this work. The wake Is contained between two free streamlines. Following Jandali's technique (1), the wake flow is created by positioning sources on the airfoil surface in that region exposed to the wake. The actual flow in the wake region is ignored, and the base pressure is taken to be constant at the experimental value. The theory agrees well with the results obtained by Jandali.

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