On sound generated from the interaction of two inviscid coaxial vortex rings moving in the same direction

Sound generation due to the interaction between two inviscid coaxial vortex rings moving along a common axis in the same direction is investigated numerically by using the method of contour dynamics and the far field equations. The results show the occurrence of the slip-through process, incomplete slip-through, coalescence and partial coalescence. They also illustrate that the radial accelerations and the rate of change of the axial accelerations of the vorticity centroids of the vortex rings are important in the generation of sound during the interaction. The axial separation of the vorticity centroids of the vortex rings and the third time derivative of the vortex impulse are found to be important only in the case of partial coalescence. As the vortex ring interactions considered in the present study are found in axisymmetric jets, the presents results suggest that the jerk and acceleration of flow structures may be related to the generation of jet noise at low Mach number.