NACA-RM-E53H25

Abstract

INTRODUCTION <br>Increased attention is currently being directed to the problem of after body aerodynamics, since after body drag frequently represents an appreciable portion of the total body drag of aircraft and missiles. In the case of engine-in-fuselage and nacelle configurations. The problem of predicting the flow field over after bodies or boattails is complicated by interference effects from the propulsive jet that issues from the base of the body. This jet disturbs a flow that is already contaminated by heavy boundary layer and that is subject to wing and tail interference effects. In addition, the flow is attempting to negotiate the adverse pressure gradient usually present over at least the rearmost portions of the boattail. Consequently, the details of the problem are complex. <br>In the present report an attempt is made to summarize some of the results of current NACA research on the problem of jet effects. Emphasis is placed on providing definition of the various phases of the problem, as well as on presenting some of the important concepts and parameters that contribute to the understanding of these phases. Previous research on the subject of jet effects on external aerodynamics may be found in references 1 to 7. The majority of the data contained herein were obtained from recent unpublished sources.