Parabolized stability equation (PSE) models for the prediction of mixing noise in turbulent jets: nonlinearity and comparison with experiments*

The wavepackets responsible for the generation of the dominant low-frequency noise of turbulent round jets are modeled via PSE. Previous experience shows that wavepackets delivered by linear PSE are in agreement with pressure fluctuations on a near-field microphone array. Nonlinear interactions between PSE modes is the subject of the present effort. Pressure fluctuations in the near-field and hot wire measurements at the jet centerline are used to determine initial amplitudes for the PSE computations, and then perturbed randomly to introduce some degree of nondeterminism. A projection technique is used to compare the noise radiated to the far-field by wavepackets with experiments. First results indicate that nonlinearity is not a determinant factor in the wavepackets evolution, especially for unheated, low Mach number jets, while small variations in the initial conditions might introduce $O(1)$ changes.