Wave propagation in vortices and vortex bursting

Abstract

The propagation of pressure waves in a Lamb–Oseen vortex has been investigated both by three-dimensional direct numerical simulations as well as a set of large-eddy simulations. The pressure wave is initiated by locally increasing the core radius of a Lamb–Oseen vortex at its edge. This wave travels along the vortex axis towards the region with a thinner core radius. Behind the wave the axial velocity increases so that sufficient swirl may trigger the helical instability. An abrupt change of flow structure in the vortex core is observed in the case of intersecting pressure waves: this phenomenon is known as vortex bursting. A vortex system composed of two symmetric counter-rotating vortices, which is similar to that of an aircraft has also been investigated by means of large-eddy simulations. In the far-field region the system develops linear instabilities such as the Crow instability, which is characterized by a large-scale symmetric sinusoidal deformation resulting in the reconnection of the two vortices. It also demonstrates the occurrence of helical instability and vortex bursting.