Accelerated Method for Predicting Acoustic Far Field and Acoustic Power of Rotating Source

Visualization of acoustic pressure and acoustic velocity field and computation of acoustic power are meaningful to investigate noise radiation and propagation mechanism of turbomachines. However, the conventional surface integral method is very time-consuming because the acoustic response for numerous source–observer pairs should be numerically computed one by one. This paper presents an accelerated method for predicting acoustic pressure and acoustic velocity in the acoustic far field radiated by rotating sources. The accelerated method is derived based on a spherical harmonic series expansion method, which explicitly describes the variation of the acoustic pressure and acoustic velocity with the radial coordinate and azimuthal angle of the observer in acoustic far field. In the proposed accelerated method, only the acoustic pressure of a few reference observer points with different polar angles is directly computed by numerical integration, whereas the acoustic pressure and acoustic velocity of the other observers are fast computed using the interpolation method. Moreover, an accelerated method for computing the acoustic power is also developed, which avoids both the numerical integral of the observer surface and computation of the acoustic velocity. Numerical illustrations indicate that the accelerated method has a good accuracy and is more efficient than the conventional numerical integral method.