Low-dimensional model of a supersonic rectangular jet

The proper orthogonal decomposition method is applied to the analysis of particle image velocimetry data obtained for a supersonic rectangular jet operated at underexpanded conditions. Phase-locked velocity field data were used to calculate the eigenfunctions and the eigenvalues. It was found that a large fraction of the total energy is contained within the first two modes. The essential features of the jet are thus captured with only two functions. A low-dimensional model for the dynamical behavior is then constructed using Galerkin projection of the isentropic compressible Navier-Stokes equations. The reduced model compares reasonably well with the experimental findings.