Experimental examination of the leading-edge suction analogy

The potential and vortical components of the normal force and their chordwise distribution, as defined by the Leading-Edge Suction Analogy (LESA), as well as the normal force itself and its chordwise distribution, were obtained experimentally and were compared with the predicted results. The comparison was carried out for the delta wings having leading-edge sweep angles of 75 and 60 deg. The experimental results were obtained from surface pressure measurements by invoking the linearized potential-flow wing theory, which was also used in the derivation of LESA. The comparison shows that, for the low-aspect-ratio wing, the agreement between measured and predicted results is good-in the 0-20 deg incidence range. In the high-aspect-ratio wing, the differences between experiment and theory are large for C_NP, C_Ny, and their longitudinal loadings, and considerably smaller for C_N. Thus, LESA appears less valid for the high-aspect-ratio wing than was previously thought on the basis of a comparison of the C_N values only.