NACA-RM-A9F16

Abstract

INTRODUCTION <br>Because many present-day airplanes are designed to fly in or through the high subsonic and transonic speed range, the need for data on air inlets at these velocities has become increasingly urgent. Although some data are available on nose inlets, little research has been done on submerged inlets in the transonic speed range. Data obtained up to a Mach number of 0.875 on an NACA submerged inlet have shown that satisfactory air-induction characteristics could be attained at subsonic speeds. <br>This report covers an investigation made in a wind tunnel to study the characteristics of submerged inlets at subsonic and transonic speeds. <br>The inlets were placed in one wall of the wind tunnel test section. Because facilities for testing at transonic speeds are limited and the testing techniques are difficult, the present means of simulating duct entrances has been used as an expedient to obtain qualitative results. A comparison is made between two forms of the same basic submerged-type intake. These two inlets, one simulating an intake with parallel ramp walls and the other an intake with divergent ramp walls (an NACA sub-merged inlet), are compared on the basis of pressure recovery. This study should give a better understanding of the operation of submerged inlets in the transonic speed range and serve as a useful guide to the designer. <br>Some design considerations for extending the useful operating range of submerged inlets at transonic&#160; speeds are discussed.