Identification of near sound field boundary and far field noise predictions.

摘要

This dissertation presents an improved computational method that allows accurate determination of near sound field boundary and far field noise predictions. A computational fluid dynamics solution is used for nonlinear near-field pressure calculations. For the far field sound propagation prediction, both the Kirchhoff integral method and the finite element method are used and results are compared. Kirchhoff formulation is used to obtain the sound pressure in the far field in terms of a surface integral of the surface element pressure. Acoustic pressure history represents input for a Kirchhoff formulation for acoustic far field predictions. The prediction of acoustic loading is essential to provide a necessary input for the determination of the location of the Kirchhoff surface. For finite element modeling, the Gradient Adaptive Transfinite Element (GATE) family is adopted owing to its variable number of nodes and order of approximation for multiple field variables to an existing sub-domain.;Computational simulations included are monopole, cavity acoustics and rocket noise propagation problems. Results show that the newly developed method of locating the near field boundary helps improve far field predictions.