The Modified Complementary Technique applied to the Mach 0.85 axisymmetric jet for noise prediction.

Abstract

The Complementary Techniques 6 are modifled to estimate the most energetic turbulent features of a Mach 0.85, axisymmetric jet in the prominent sound-source regions of the ∞ow via Spectral Linear Stochastic Estimation. 11,28 This model estimate is three-dimensional, comprises all three components of the velocity fleld and is time resolved. The technique employs the pressure fleld as the unconditional input, that which is measured within the hydrodynamic periphery of the jet ∞ow where signatures (pressure) are known to comprise a reasonable footprint of the turbulent large-scale structure. Spectral estimation coe‐cients are derived from the joint second order statistics between coe‐cients that are representative of the low-order pressure fleld (Fourier-azimuthal) and of the low-order velocity fleld (POD). A bursting like event is manifest in the model estimate and is similar to what was found in the low-speed jet studies. 9 Lighthill’s analogy is efiected and a prediction of the far-fleld acoustics is performed. This work, thus constitutes a benchmark for developing dynamical system models from hydrodynamic pressure signatures for estimating and predicting the behavior of the deterministic energy containing events that govern many of the physical constituents in turbulent ∞ows.