高亜音速ジェット騒音のLarge-Eddy Simulationにおける入口擾乱の影響

概要

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Subsonic jets at Mach number Mj = 0.9 are computed using compressible Large Eddy Simulation and Kirchhoff method in order to investigate the effects of the inflow forcing on the flow and sound field. Four parameters are varied in the jet inflow: the use of the first modes in the ring vortex excitation involving several azimuthal modes, the forcing amplitude, the thickness of disturbances, and the existence of the inflow forcing. It is confirmed that there are significant differences whether the disturbances are added or not. The inflow forcing parameter that has the most influence on the flow and sound field is the azimuthal modes. It is shown that the inflow forcing takes an important role to destroy the coherence of velocity disturbances on the shear layer and prevents high amplitude velocity and pressure fluctuations that are caused due to axisymmetric vortices. When first modes in several azimuthal modes are removed, the flow field and far field sound pressure levels are relatively consistent with experimental data.