High Angle Of Attack Aerodynamics

The aerodynamics of aircraft at high angles of attack is a subject which is being pursued diligently, because the modern agile fighter aircraft and many of the current generation of missiles must perform well at very high incidence, near and beyond stall. However, a comprehensive presentation of the methods and results applicable to the studies of the complex aerodynamics at high angle of attack has not been covered in monographs or textbooks. This book is not the usual textbook in that it goes beyond just presenting the basic theoretical and experimental know-how, since it contains reference material to practical calculation methods and technical and experimental results which can be useful to the practicing aerospace engineers and scientists. It can certainly be used as a text and reference book for graduate courses on subjects related to high angles of attack aerodynamics and for topics related to three-dimensional separation in viscous flow courses. In addition, the book is addressed to the aerodynamicist interested in a comprehensive reference to methods of analysis and computations of high angle of attack flow phenomena and is written for the aerospace scientist and engineer who is familiar with the basic concepts of viscous and inviscid flows and with computational methods used in fluid dynamics.

A computational method for lateral-directional aerodynamics of fighter configuration is developed. The leading edge vortices are represented by free vortex filaments which are adjusted iteratively to satisfy the force-free condition. The forebody vortex separation, both symmetrical and asymmetrical, is calculated using slender body theory. Effect of boundary layer separation on lifting surfaces is accounted for using the effective sectional angles of attack. The latter are obtained iteratively by matching the nonlinear sectional lift with the computed resulted based on lifting surface theory. Results for several fighter configurations are employed for comparison with available data. It is shown that the present method produces resonable results in predicting sideslip derivatives, while role and yaw rate derivatives do not compare very well with forced oscillation test data at high angles of attack. Industrial usage of this has produced mixed results. At this time, the use of these methods in a production manner is not recommended.