Numerical Simulation of Subsonic and Supersonic Jets

Abstract

In this study, round compressible turbulent jets at various mach numbers are simulated using several turbulence models and the results are compared with experimental data available in the literature. Both subsonic and supersonic jets are considered. The simulations have been carried out using the commercial software FLUENT. The flow is taken to be axi-symmetric, compressible and turbulent. A computational domain of size 40D X 10 D, where D is the nozzle exit diameter, has been used for subsonic jets. For supersonic jets, the size of the domain is 20D x 5D. A structured mesh is used, with clustering of nodes near the nozzle exit plane and the jet axis. The grid used for subsonic jets consists of about 32,000 cells, while a slightly higher number of cells are used for supersonic jets. For all the results reported here second order accurate discretisation has been used and the mass imbalance is five orders of magnitude less than the total mass flow through the computational domain. Numerical results from the simulation of cold and hot subsonic jets (Mach 0.6 and 0.9) are compared with experimental data reported by Simonich et al (AIAA Journal, Vol. 9, No. 11, 2001, pp 2062-2069). Results from the supersonic jet simulations (Mach 1.4 and 1.8) are compared with experimental data reported by Panda and Seasholtz(NASA TM 2003-21239, 2003). The agreement between simulations and the experimental data is found to be quite good. The simulations are able to predict the core length and the decay in both the axial and radial directions very well. In addition, far-field noise spectra at dierent locations of the heated subsonic jets, have been simulated by Kircho’s surface integral method. The near field two dimensional axi-symmetric pressure data has been extended to three dimensions to obtain pressure data on a coaxial cylindrical integration surface of diameter approximately 20D. The numerically obtained frequency spectrum at dierent observer locations are compared with the experimental data of Simonich et al.