INTRODUCTION This Item provides an empirical means of estimating the base and boat-tail pressure-drag coefficients of axisymmetric cylindrical bodies with circular-arc boat-tailing for Mach numbers up to 1.3. The method applies to bodies which are at zero angle of attack with cylindrical midbodies immediately in front of the boat-tailing. The method assumes that the overall pressure drag of an axisymmetric body can be sub-divided into forebody@ boat-tail and base pressure drags. Experience suggests that the boat-tail and base pressure drags can be regarded as independent of the forebody drag provided that the cylindrical midbody between the forebody and boat-tail is more than about three body diameters in length. It is further assumed that the boundary layer is turbulent and that there is no jet flow through the base. The data used in deriving the method in this Item were obtained from the wind-tunnel tests reported in Derivations 1 to 3. A worked example is given in Section 6. Base and boat-tail drag data for conical afterbodies may be obtained from Item Nos 76033 and 77020 (References 7 and 9) at subsonic speeds@ Item No. 78041 (Reference 10) at transonic speeds and Item Nos 79022 and Aero B.S. 02.03.04 (References 11 and 4) at supersonic speeds.
ESDU 96012-1996 history
1996ESDU 96012-1996 SUBSONIC AND TRANSONIC BASE AND BOAT-TAIL PRESSURE DRAG OF CYLINDRICAL BODIES WITH CIRCULAR-ARC BOAT-TAILS