Direct Numerical Simulation of Internal Noise Propagation and Radiation

Direct numerical simulations of engine internal noise propagation and its radiation to the ambient are performed in the present paper. A simplified noise source model is used to simulate the fan or other noise sources inside a jet engine duct. An outer free field is attached to the engine duct to study the radiation of the generated noise. Eulers equations are used to study the sound propagation inside the nozzle as well as the radiation in the outer free field. High accuracy finite difference scheme is used to guarantee accurate numerical results. Proper numerical boundary conditions are imposed at the boundaries of the outer free field to let the acoustic waves leave the computational domain without generating noticeable reflections while allowing for the entrainment.