The thesis deals with some new applications of the wake source model, a two-dimensional incompressible potential flow model used for bodies experiencing flow separation. The body contour is conformally mapped to a circle, for which the flow problem is solved using source singularities to create free streamlines simulating the separating shear layers. In common with other inviscid theories, it generally requires the pressure in the separated flow region, and the location of separation if boundary-layer controlled. Different mapping sequences and flow models have been constructed for the following five problems, 1. the trailing-edge stall for single element airfoils, 2. flat plates with separation bubbles, 3. separation bubbles upstream of spoilers with downstream wakes, 4. spoiler/slotted flap combinations, at which the spoiler inclination is arbitrary, and 5. two-element airfoils near (trailing-edge) stall. Predictions of pressure distribution are compared with wind tunnel measurements, and good agreement is found in cases 1 and 5. The initial shape of the separation streamlines also appears to be satisfactory. Results in cases 2 and 3 are promising although more work is needed to improve the bubble shapes and their pressure distributions. Partial success has been achieved on spoiler/ slotted flap configurations, depending on the spoiler inclination. For strong wake effect on the flap (e. g. δ = 90° ), the model predicts a very high suction peak over it. Whereas the experimental data resemble a stalled distribution even though flow visualization indicates the flap to be unstalled. This may be related to a limitation of the method, also noted in the separation-bubble problems, that it cannot specify a complete boundary condition on a free streamline. This discrepancy diminishes as the spoiler angle becomes smaller (e. g. δ = 30° ) in the cases of higher incidences so that the wake boundary tugs away from the flap sooner. / 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

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Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Ekaterinaris, John A. ; Platzer, Max. "September 1990." Description based on title screen as viewed on December 21, 2009. DTIC Identifier(s): Dynamics, leading edges, airfoils, dynamic stall, oscillating airfoil, pitching airfoil, leading edge geometry, pressure gradient, theses. Author(s) subject terms: Dynamic stall, oscillating airfoil, pitching airfoil, leading edge geometry, pressure gradient. Includes bibliographical references (p. 111-112). Also available in print.

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