A Generic Centerline Velocity Decay Curve for Initially Turbulent Axisymmetric Jets

Abstract

Recently the authors introduced a length scale which effectively collapsed the near field centerline development of velocity and mass fraction for variable density axisymmetric jets whose initial conditions correspond to those of fully developed turbulent pipe flow. The new length scale incorporated the initial mass, momentum, and turbulence intensity per unit area to capture the Reynolds number dependence of near field development for the velocity and scalar distributions observed in low Reynolds number turbulent jets. The presents paper extends the analysis for a constant density jet to the intermediate and self-similar far fields further downstream using a dynamic length scale based on the local centerline turbulence intensity. The normalized mean velocity distributions of an air jet collapse over the entire flow distance investigated velocity distributions of an air jet collapse over the entire flow distance investigated velocity distributions of an air jet collapse over the entire flow distance investigated when the axial distance is normalized by the proposed length scale, thus scaling the virtual origin shift and effectively incorporating the Reynolds number dependence.