Jet noise prediction: Past, present and future

Jet noise continues to be an important contributor to the total aircraft noise on takeoff, and the prediction of jet noise based on relatively simple models is discussed. Jet noise predictions are either based on a company's proprietary experimental database or are based on a Reynolds-averaged Navier-Stokes (RANS) simulation for the jet's mean flow, coupled with an acoustic analogy. Detailed calculations of the full time-dependent, three-dimensional near field, coupled with an extrapolation method to extend the solution semi-analytically to the far field, have been very effective. A simple model is proposed for the generation and radiation of noise by the large scale turbulent structures in the jet shear layer. Models based more closely on experimental measurements, such as those given by Harper-Bourne. Comparisons were also made with previous measurements in other anechoic jet facilities and problems with these prior measurements were identified.