MINISTRY OF SUPPLY AERONAUTICAL RESEARCH COUNCIL , REPORTS AND MEMORANDA Boundary = Layer

The report describes the results of traverses of the boundary-layer and wake encountered in a small supersonic tunnel at a Mach number of 2.5. The tunnel was arranged with two throats in parallel formed by two shaped walls enclosing a shaped central element. Both the laminar and turbulent boundary-layers were encountered and compared with existing experimental and theoretical results. The frictional drag of the central element as deduced from the wake traverses is in close agreement with that calculated from considerations of laminar boundary-layer growth over the surface of the element. The tests also provide information relating to the design of nozzle profiles, particularly at the point of inflexion, where the changes of pressure gradient may have a serious effect on the boundary-layer and on the velocity distribution. 1. Introduction.-Recent tests on a two-dimensional multiple-throat nozzle consisting of eleven small nozzles placed in parallel and mounted in a 5.5× 5.5 in. supersonic wind-tunneP indicated that a more refined investigation of the growth and strength of the wakes, arising from the nozzle elements, was desirable.