A theory is presented for the calculation of the pressure distribution and lift for arbitrary thick airfoils fitted with normal upper surface spoilers in two dimensional incompressible flow. Airfoil shape and angle of attack and spoiler location and height are arbitrary and unrestricted. The theory uses a sequence of conformal transformations from a basic flow past a circle, with one or two sources on that part of the circle corresponding to the surface of the airfoil and spoiler exposed to the wake. The flow inside the separating streamlines is ignored, and the upper surface pressure downstream of the spoiler is taken as an empirical parameter, assumed constant. The sources in the wake permit satisfaction of Kutta conditions with the desired pressure at the spoiler tip and airfoil trailing edge. Features of the theory include good prediction of loading distribution, a finite wake width and a pressure distribution on the separating streamlines decreasing asymptotically towards the free stream value at infinity. The theoretical predictions are compared with lift and pressure measurements on a Joukowsky airfoil of 11% thickness and 2.L\% camber, and with lift measurements on a 14% thick Clark Y airfoil. Both airfoils were tested through a range of angle of attack with spoilers of 5 and 10% chord height, each at several locations. Good agreement is found. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

An experimental study has been carried out on an airfoil with slotted flap and spoiler using Joukowsky profiles. Pressure distributions were measured as functions of angle of attack, flap deflection angle, spoiler size and inclination. The results are uncorrected for wind tunnel wall effects but the data base is available to carry out the corrections. The results will be used to compare with predictions of a theoretical model, yet to be worked out, which combines work previously done by Williams, Jandali, Parkinson and Yeung. This theory will involve the potential flow about a two-element 'near'-Joukowsky airfoil system. The secondary airfoil is a simulated slotted flap. Various size spoilers are introduced to the system at arbitrary angles of inclination using methods proposed by Parkinson and Yeung. The experimental results are qualitatively reasonable and some interesting effects are observed. The behaviour of spoilers, when used with slotted flaps at various deflection angles, corresponds well with requirements of aircraft in approach or landing situations. Similarly, the use of slotted flaps alone provides the high lift at low angle of attack which is beneficial to aircraft taking off. Some recommendations are proposed for further testing with this equipment. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate