A hybrid analysis methodology for improved accuracy inlow cost jet noise modelling

摘要

The tools currently available for jet noise prediction range from high precision, highrncost approaches such as DNS and LES, to lower cost methods which require the turbulence to be modelledrnin some way (e.g. statistical and SNGR type approaches). Where the latter are concerned thernerror incurred in modelling the turbulence can often be orders of magnitude greater than the acousticrnenergy generated. It is thus imperative that the models used in these approaches be extremely accurate.rnDNS or LES computations give the kind of precision necessary, but at a prohibitive computational cost.rnThis work comprises a hybrid analysis for improved accuracy of low cost noise prediction schemes.rnThe methodology consists in using data from a LES (this data having been validated by experiments)rnto validate and improve the models used in both statistical and SNGR jet noise prediction schemes.rnAnalytical models for the spatiotemporal velocity corrlelation tensors which have been developed torndeal with the inhomogeneous, anisotropic structure of a jet are compared with their numerically generatedrncounterparts from the LES. The spatial evolution of their form and its relation to local quantitiesrnsuch as the integral scales and turbulence intensities are investigated using the LES, with a view tornunderstanding how the analytical models can be adapted so as to capture this evolution.