Hybrid DRP-BEM method for plume acoustics
AlSalem, Khaled Salem
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In this work the noise of turbulent fire plumes is investigated. A hybrid numerical method is developed for this purpose. The method consists of using Large-Eddy-Simulation (LES) for construction of the acoustic source terms, the dispersion-relation-preserving (DRP) scheme for solving the linearized Euler equations in the near field, and the boundary element method (BEM) for far field propagation. The developed method is used to investigate the acoustics of fire plumes. Lighthill's formulation of the source term (Lighthill, 1952) is used in this study in addition to an energy term that accounts for the direct combustion noise due to the change of entropy. The acoustics of two and three dimensional reacting plumes are investigated. For the two dimensional case, far field propagation using the boundary element method was predicted with large number of constant elements. In the three dimensional case, linear elements were used to reduce the number of elements needed for accurate far field propagation. The predicted fields show that fire plumes produce a broad band noise of low amplitude. The three dimensional fire plume produced lower entropy noise but higher direct combustion noise.