THEORETICAL AND EXPERIMENTAL INVESTIGATION OF THE ISOTHERMAL AXISYMMETRIC TURBULENT FREE JET (CIRCULAR, BOUNDARY)

The development of the isothermal axisymmetric turbulent free jet is traced experimentally and theoretically from the jet source through the near-field into the fully developed region. The experimental and numerical investigations are described in detail and include description of experimental apparatus and technique, numerical analysis, and empirical and numeric results.; Hot-film anemometry data for two differing jets are computer reduced to yield extensive mean velocity and turbulence intensity profiles throughout the regions of jet development. These data are compared to that of previous studies and subsequently validated as a result of its close correlation to existing empirical models.; The generalized governing equations of anisotropic turbulence based on a Boussinesq/Prandlt viscosity model are derived for a cartesian geometry. This derivation includes a physically realistic and complete energy spectrum equation in the form of the so-called Reynolds-stress closure viscosity models. The cartesian system is transformed to cylindrical geometry and the boundary layer assumptions are applied together with the boundary conditions associated with axisymmetric free jet and dimensionless parameters to yield a dimensionless governing equation set for the jet problem at hand.; A simple Boussinesq/Prandlt kinematic viscosity model is assumed and the governing equations (excluding the more complex energy spectrum equation) are numerically solved with a finite element approach which utilized a cubic basis function to match numeric profiles to experimental data, thereby characterizing the assumed turbulent kinematic viscosity throughout the development region. The exponential viscosity profile derived as a result of this characterization is shown to correlate closely with known jet behavior and is proposed as a bench-mark for future modeling of the energy spectrum Reynolds-stress closure model as presented herein.