Numerical prediction of dipole sound based on Lighthill-Curle's equation gives Iittle information on the structure of sound sources. On the other hand, ahybrid method that combines the large eddy simulation (LES) and the compact Green's function proposed by Howe provides detailed information on the vortices in the flow that most contribute to the generation of sound . However, when the dipole sound is evaluated from themomentum change in fluid inside a finite computational domain, the result does not in general agree with the sound evaluated from the fluctuating pressure on the body surface because contribution from vortices outside the computational domain is not taken into account. In this study, the balance of momentum in a finite computational domain is considered strictly, and the effect of outer vortices is replaced with contribution from inner properties by using an imaginary velocity potential ψi. This method allows quantitative prediction of dipole sound and also gives accurate information about sound sources.

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