NACA-TN-3221

Abstract

A study has been made of existing experimental and theoretical results for an inclined flat plate of infinite span, and of the extent to which the results are indicative of those for thin airfoil sections. The study included an examination of the flow about an inclined plate, the forces on the plate, and the adequacy of theory in predicting the forces. Theories considered were the well-known thin-airfoil theory, and the theory of discontinuous potential flow and modifications thereof. The effects of compressibility were examined. <br>The results of the study indicate that there are two important ranges of angle of attack differing by the extent of flow separation on the upper surface. At angles of attack below about 8&#176;, flow separation and reattachment occur, and the well-known thin-airfoil theory is adequate for predicting the lift and normal force on the plate. Similar results were noted for thin airfoil sections. At the higher angles of attack the flow is completely separated from the upper surface as is assumed in the discontinuous potential-flow theory for an inclined flat plate. The theory, however, is entirely inadequate. A simple empirical modification of the theory is suggested; the modified theory provides a good first approximation of the forces and moments on thin airfoil sections with the flow completely separated from the upper surface. Effects of compressibility were evident from the available experimental data; however, the effects were not defined sufficiently for evaluating methods of prediction.