Direct simulation of sound generated by collisions of two vortex rings
Abstract
In order to study the generation mechanism of sound, flow fields produced by collisions of two vortex rings are simulated numerically. By a finite difference method, the three-dimensional, unsteady, compressible Navier-Stokes equations are solved not only for a near-field but also for an acoustic far-field. Effects of the collision angle between the two vortex rings on the flow fields as well as on the generation mechanism of sound are examined. The results show that for the case of head-on collision, acoustic sounds are generated twice and both sounds have a quadrupolar nature. The pressure peaks of the sounds decay in inverse proportion to the distance from the origin, in agreement with theory. For the case of oblique collision, octupolar components appear in addition to the quadrupolar component. The generation mechanism of sound becomes complicated more and more with decreasing collision angle.
Key Words
DNS CAA Sound Vortex RingsPreview
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References
- Colonius, T., Lele, S. K. & Moin, P. (1997) Sound generation in a mixing layer. J. Fluid Mech., 330, 375–409.MATHCrossRefADSGoogle Scholar
- Adachi, S., Ishii, K. & Kambe, T. (1997) Vortex sound associated with vortexline reconnection in oblique collision of two vortex rings. ZAMM Z. angew. Math. Mech., 5, 1–5.Google Scholar
- Inoue, O. & Hattori, Y. (1998) Direct simulation of acoustic sound generated by two vortex rings. AIAA Paper 98-2329, 4th AIAA/CEAS Aeroacoustics Conference, A Collection of Technical Papers, Part 2, 758–764 Google Scholar
- Kambe, T., Minota, T. & Takaoka, M. (1993) Oblique collision of two vortex rings and its acoustic emission. Phys. Rev. E, 48, 1866–1881.CrossRefADSGoogle Scholar
- Kida, S., Takaoka, M. & Hussain, F. (1991) Collisions of two vortex rings. J. Fluid Mech., 230, 583–646.MATHCrossRefADSMathSciNetGoogle Scholar
- Lele, S. K. (1992) Compact finite difference schemes with spectral-like resolution. J. Comp. Phys. 103, 16–42.MATHCrossRefMathSciNetADSGoogle Scholar
- Lele, S. K. (1997) Computational aeroacoustics: a review. AIAA Paper 97-0018 Google Scholar
- Minota, T. & Kambe, T. (1986) Observation of acoustic emission from head on collision of two vortex rings. J. Sound Vib., 111, 51–59.CrossRefGoogle Scholar
- Mitchell, B. E., Lele, S. K. & Moin, P. (1995) Direct computation of the sound from a compressible co-rotating vortex pair. J. Fluid Mech. 285, 181–202.MATHCrossRefADSMathSciNetGoogle Scholar
- Poinsot, T. & Lele, S. K. (1992) Boundary conditions for direct simulation of compressible viscous flows. J. Comp. Phys. 101, 104–129.MATHCrossRefADSMathSciNetGoogle Scholar
- Tam, C. K. W. (1995) Computational aeroacoustics: issues and methods. AIAA J. 33, 1788–1796.MATHCrossRefADSGoogle Scholar