Structure of turbulent bulges in an axisymmetric jet

Abstract

Conditional sampling techniques are used to determine the shape of ensemble averages of the axial (u) and radial (v) velocity and temperature (e) fluctuations and their products uv, ue and ve, within turbulent bulges of a slightly heated axisymmetric jet with a co-flowing external stream. Ensemble average shapes are obtained at four radial positions in the intermittent region of the flow. In bulges of relatively large duration, ensemble averages of v and e rise fairly sharply near the front of a bulge and decrease rather gradually near the back. Ensemble averages of u are nearly symmetrical within the bulge. The mean values of ensemble averages of u and e within a bulge are essentially independent of the duration of the bulge. The largest contribution to the Reynolds shear stress or heat flux generally arises from bulges of medium duration but, near the jet axis, bulges of relatively short duration provide a significant contribution. For a bulge of specified duration, a major contribution to the Reynolds shear stress or heat flux occurs in the vicinity of the back near the axis of the jet but close to the front elsewhere.