INTRODUCTION

This Item gives pressure distribution data for the flow of air* over four families of blunt forebody at zero incidence; ellipsoidal, spherically-curved nose with radiused shoulder, spherically-blunted cone and spherically-blunted tangent ogive. The families chosen (see Section 3) cover most of those likely to be used in missile and re-entry body applications. Included among the families are those considered in Item No. 68021 (Reference 21) and Item No. 80021 (Reference 24) and as such the present Item acts as a companion to those two.

The ranges of geometry and Mach number covered for each family are as wide as possible dependent on the availability of data. The pressure distribution data are presented (Section 4) in a direct form as a ratio of the local static pressure to the stagnation pressure at the nose of the forebody, while methods of estimating the stagnation pressure itself are given in Section 5. The abscissal parameter was selected as that being most appropriate to the family under consideration. In this respect data for forebody fineness ratios (l_f/Dof 0.5 or less are presented against a dimensionless radial co-ordinate, Y/R, which satisfactorily accommodates the case of the flat face, while for forebody fineness ratios of 0.5 or more the data are presented against an appropriate dimensionless axial co-ordinate.

Section 6 provides a means of estimating, for inviscid flow, the surface Mach number distribution and the temperature distribution with no heat transfer from the corresponding pressure distribution.

Section 7 considers the accuracy and applicability of the data, which will typically be used in loading applications.

Section 8 lists the sources of data, both theoretical and experimental, used to derive the data given while Table 10.1 provides a breakdown of the sources of data used for each pressure distribution Figure.

Section 9 gives a worked example concerning a typical application of the Item.

Appendix A summarises the geometrical relationships defining the forebody shapes used in this Item. Also included are relationships for surface length, which is sometimes used in experimental work, for example in defining the pressure hole locations on test bodies.

The data for the hemispherical head are used in Appendix B to describe the flow development over a typical blunt body as the free-stream Mach number traverses the full range from low subsonic to high supersonic.

* Any formulae or theoretical methods used to generate data in this Item requiring a value of the ratio of specific heat capacity at constant pressure to the specific heat capacity at constant volume used 1.4 for air.