Abstract:

ESDU 90020 provides a simple theoretically-based method for predicting the upwash at any point in the flow field ahead of the wing. The method, based on the "Yaggy-Rogallo" method, combines contributions from those airframe components that are planar lifting with contributions from the "body-like" essentially non-lifting components, with allowance for interference. For lifting surfaces a graphical method was developed from a correlation of a large number of calculations using the original approach but with spanwise loadings from lifting-surface theory. A correction factor to obtain results out of the plane of the surface was developed using a single swept horseshoe vortex. This approach greatly reduces the work required to calculate wing upwash. The method for body-like components uses an analytical integration of an equivalent axisymmetric body by dividing it into cross-sectional segments whose sides are approximately linear. For both types of components the first-order effects of compressibility are taken into account. The method has a wide range of applications with wing-body combinations. For use with ESDU 89047 to predict normal force and moments on an inclined propeller an effective angle of attack is devised. The method was compared with test data for upwash due to isolated nacelles, upwash induced at the propeller plane for a number of wing-body-nacelle combinations, and upwash at a noseboom-mounted vane on a combat aircraft. The agreement between predictions and test results for Mach numbers up to critical is good and is discussed in detail. Two worked examples illustrate the use of the method. A Fortran program of the method is provided as ESDUpac A9020.