a Second Order Model of a Swirling Turbulent Jet
This work attempts to model turbulence in swirling flows. Equations for the second moments of the turbulent fluctuations are derived and the various unknown terms in the equation are modeled. Invariance and physical realizability are used as constraints on the model. The rapid part of the pressure correlations is modeled to second order in the anisotropy tensor, leaving three adjustable constants. Improvements are made in the models of Lumley (1978) for the pressure transport and dissipation transport terms. The third order moments are modeled by a rough approximation of the terms in the third order moment equation. The model is then put on computer and a numerical simulation of a swirling turbulent jet is performed. Several of the constants in the model are adjusted separately and the effects on the model are shown and analyzed. The constants are then adjusted to best fit the experimental data of Rose, using Morse's data as an additional guide. The model fits the experimental data for a nonswirling jet very well. It does fairly well on the swirling jet except it doesn't spread fast enough for the first few diameters. Explanations are offered for this slow spreading rate. Finally, a correction term to take into account the effects of swirl on dissipation is given which dramatically improves the swirling jet results for the first few diameters.
- Pub Date:
- Physics: Fluid and Plasma