This work presents the study of two free axisymmetric jets using computational fluid dynamics. The commercial software ANSYS® Fluent was used for the analysis. The jets were modeled based on the experimental studies of Crow & Champagne (1971) and Stromberg, McLaughlin, & Troutt (1980). The experimental jet of Crow and Champagne was a high Reynolds number, incompressible jet. To capture the turbulence in the jet, large eddy simulation was used. A grid refinement study was performed and it was determined that low mesh density produced significant numerical diffusion causing the jet to decay more rapidly. Bounded central differencing and the MUSCL scheme were both used for spatial discretization. The MUSCL scheme produced unrealistic turbulence in the jet near field. Three subgrid-scale models were used: the Smagorinsky model, dynamic Smagorinsky model, and dynamic kinetic energy model. The dynamic kinetic energy model produced the most accurate results at the cost of a 16% increase in computation time.
The low Reynolds number, high subsonic jet of Stromberg et al was tested using two different boundary conditions at the domain inlet: a velocity inlet and a mass flow inlet. Large eddy simulation with the dynamic Smagorinsky model was used to capture the turbulence. The velocity inlet produced large fluctuations in the fluid Mach number near the inlet. These fluctuations in the near field were not present in the mass flow inlet case or the experimental results. Downstream the Mach number profiles for the two different inlet cases converged to the same solution.
The results of this analysis provide verification and best practices for the use of large eddy simulation in ANSYS® Fluent. The methodology applied here can be used to analyze other cases of free shear. Additionally, the results lay the ground work for further analysis of jets and free shear including chemical reactions, heat transfer, and aeroacoustics.
|Commitee:||Darabi, Jeff, Yan, Terry X.|
|School:||Southern Illinois University at Edwardsville|
|Department:||Mechanical and Industrial Engineering|
|School Location:||United States -- Illinois|
|Source:||MAI 52/02M(E), Masters Abstracts International|
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