A numerical method for computation of sound radiation from an unflanged duct

Some issues involved in establishing a numerical model for sound radiation from a straight duct are addressed in this paper. The main ingredient of the numerical method is solutions of linearized Euler equations using a high order compact scheme. Farfield directivity is estimated through an integral solution of Ffowcs–Williams Hawkings equations. A generic test case of planar wave radiation from an unflanged duct is studied. The sound pressure level and wave propagation in the nearfield are analyzed, together with the farfield directivity. Comparison with analytical solutions shows good agreement. The effect of grid resolution on the sound radiation pattern and the construction of integration surface on the farfield directivity are discussed.