Conference_programme: 4.2 - Aircraft/Helicopter Noise

Lecture: Jet Noise Predictions in Complex Environments using a Novel LES-Nonlinear Euler Approach

Author(s): Sassanis Vasileios, Sescu Adrian, Collins Eric, Luke Edward , Harris Robert

Summary:
Jet physics of launch vehicles during lift-off involve complex phenomena such as sound reflection, diffraction and transmission, due to the interactions of the jet plume with the surrounding structures. These phenomena, which at supersonic speeds result in strong nonlinearities that propagate over long distances, affect the vibroacoustic field generated by the jet and may compromise the integrity of the vehicle. The aim of the current work is to test, validate and improve a hybrid approach for jet noise predictions of launch vehicles, which would : a) account for the nonlinear phenomena being developed in such a flow field, compared to traditional linearized methods (LEE, LNS), b) incorporate the effects of physical obstructions in the prediction of the acoustic field (compared to FW-H and Kirchhoff integral approaches), and c) deliver results of similar accuracy to a Direct Noise Computation (DNC) approach with fewer computational resources. For these purposes, a hybrid LES-Nonlinear Euler approach is employed. First, the full Navier-Stokes equations are solved in a first domain including the jet plume and the near field region to obtain the noise sources. Then, an interpolation and penalization technique is used to construct source terms for the full Nonlinear Euler equations, which are being solved in a second, extended domain to account for the far field propagation. The two domains are synchronous, but with different mesh blocking structures and densities. The method is proven to be accurate in terms of sound pressure level spectra and time histories of pressure compared to DNC simulations.

Corresponding author

Name: Mr Vasileios Sassanis

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Country: United States