EXTENDED KIRCHHOFF INTEGRAL FORMULATIONS FOR SOUND RADIATION FROM VIBRATING CYLINDERS IN MOTION

This paper presents numerical results of sound radiation from vibrating cylinders in rectilinear motion at constant subsonic speeds by using the extended Kirchhoff integral formulations recently derived by Wu and Akay (1992). In particular, the effects of the interaction between the turbulent stress field and the vibrating surface in motion are examined. Numerical results demonstrate that this interaction is significant in the near-field when the dimensionless frequency ka > 2 and the dimensionless source translational speed M > 0.1. If this interaction is completely neglected, the predicted acoustic pressure is underestimated by as much as 10 to 20 percent in the near field. The effects of this interaction, however, decrease in the far-field. The effects of surface translational motion on the resulting sound radiation are also examined. It is found that the surface translational motion has a significant effect on the resulting sound generation in both near- and far-fields. The amplitude of the acoustic pressure is approximately doubled in the forward direction when ka > 2 and M > 0.2, which corresponds to at least a 5 dB increase in the SPL value.