Abstract:
Many geophysical flows can be idealised as comprising of two-layers of different density separated by sharp interfaces. When subjected to velocity shear these interfaces support waves that can become unstable, initiating a transition to turbulence leading to mixing between the layers. This seminar will summarize the fundamental shear instabilities and touch on some of the many circumstances where they may be of practical relevance, including: vertical mixing in the atmosphere and oceans; mixing in internal hydraulic jumps; the initiation of bedforms in sand bed rivers; the upstream intrusion of salt wedges into rivers; and exchange flows between water bodies of different densities. The theoretical and experimental techniques developed in the investigation of shear instabilities have also been used to exploit an analogy between the propagation of fields around black holes and surface waves on moving water to demonstrate the viability of Hawking radiation – the process by which black holes may radiate energy.