Tests at M = 1.82 on an engine installation with boundary-layer diverter for a slender gothic wing

Abstract

This Paper should be read in conjunction with A.R.C.26912 (C.P. 866) The absolute values of the results obtained do not have a great significance. Their main interest lies in their relationship to those of C.P. 866. In these two Papers there is effectively an aerodynamic performance comparison between two philosophies of engine installation. In C.P. 866 the objective was to bury the excess area between intake entry and engine maximum cross section in the local wing structure and hence produce (within the limitations of a fixed geometry intake with all-external compression) a low drag installation. In the tests described in the present Paper no attempt was made similarly to bury this excess area when the engines were mounted four in a square per nacelle and hence it was realised that the installation would lead to high wave drag. The pressure field from the cowl forebody was then used to interfere favourably (in a lift and drag sense) with the undersurface of the wing in an effort to offset this high cowl wave drag. This philosophy was particularly accentuated in this model by the choice of short length for both forebody and afterbody of the nacelle. The particular balance desired and achieved when using pressure fields, that produce drag, also to produce lift, is a delicate one (see R & M 3528) and the results of this investigation show that this particular design was probably quite far from the optimum arrangement.