Abstract:

ESDU 78041 gives graphs enabling both boat-tail and base pressure drags to be predicted on axisymmetric bodies with at least three diameters of constant diameter section upstream of the boat-tail, at zero incidence, with a turbulent boundary layer and no jet efflux. The graphs were obtained by a correlation of experimental test data drawn from the literature. The range of the data was limited to boat-tail angles less than 16 degrees and graphs are given for the Mach number range of 0.9 to 1.3 plotting both drag coefficients as a function of boat-tail diameter ratio. For boat-tail angles of 30 degrees and above the flow is fully-separated and the drag is given by the base drag of a cylindrical body of diameter equal to the maximum body diameter; a graph gives those values. In the range between 16 and 30 degrees, flow separation occurs and no data are available to provide interpolation. The base and boat-tail drags are given respectively at subsonic speeds in ESDU 76033 and ESDU 77020 and at supersonic speeds by ESDU 79022 and ESDU Aero B.S.02.03.02.