AERODYNAMIC AND RADIATION HEATING DURING FLIGHT

Abstract

Abstract : Aeronautical Research Council (Gt. Brit.). TURBULENCE IN THE MIXING REGION OF A ROUND JET, by P. O. A. L. Davies, M. J. Barratt, and M. J. Fisher. 24 Apr 62, 22p. ili AD-277 965Div. 9 U (TISTA/VGW)Aeronautical Research Council (Gt. Brit.). TURBULENCE IN THE MIXING REGION OF A ROUND JET, by P. O. A. L. Davies, M. J. Barratt, and M. J. Fisher. 24 Apr 62, 22p. illus. 17 refs. (ARC rept. no. 23728; N 200; FM 3181) (In cooperation with Southampton U. (Gt. Brit.)) Unclassified repo t DESCRIPTORS: *Jet mixing flow, *Jets, Air, Gas flow, Noise generators, Shear stresses, Velocity, Anemometers, Tests, Wind tunnel nozzles, Aerodynamics, Turbulence. Measurements in the mixing region of a one inch diameter cold air jet are described for Mach numbers from 0.2 to 0. 55. The statistical characteristics of the turbulence in the first few diameters of the flow may be expressed in terms of simple kinematic similarity relationships. These are based on the jet diameter and the distance downstream from the jet orifice as length scales, and the inverse of the local shear as a time scale. Experiments showed that the integral time scale of the turbulence in a frame convected with the maximum energy of the turbulent motion is inversely proportional to the local shear. The local intensity of the turbulence is equal to 0.2 times the shear velocity, defined as the product of the local integral length scale of the turbulence with the local shear. The local intensity is defined as the r.m.s. value of the local velocity fluctuations divided by the jet efflux velocity. The length scale is proportional to the distance from the jet orifice, while the maximum shear is also related to this distance as well as the jet efflux velocity. These two similarity relations break down close to the jet orifice and change beyond the first six or so diameters downstream.