Flame dynamics involve many effects (hydrodynamics, acoustics, thermal expansion, reaction and more), and they are known to display unstable behaviour in a large variety of configurations. These instabilities can be underpinned by rich interactions, for instance between shear mechanisms, flame front dynamics and thermo-acoustic radiation. I will visit three very different scenarios where instabilities manifest themselves, and examine these with linear analysis:
1. an “anchored” flame in the wake of a bluff body,
2. a V-shaped flame issuing from an annular nozzle,
3. a conical Bunsen flame of premixed hydrogen.
The focus of the seminar will be on the last configuration, where a sub-unity Lewis number leads to the onset of “polyhedral” flame shapes.