Plumes , entrainment and B . R . Morton

Bruce Morton’s early research career was centred on the dynamics of plumes, which is the focus of most of this article. As described below, the process of entrainment plays an important role in plume dynamics, at least in the mathematical models he studied. And in his teachings he made a point of emphasising the importance of vorticity in understanding fluid flow. ‘Vorticity is the flow field’, a truism he was fond of saying, which of course is true except for the irrotational part of the flow, governed by (for incompressible fluids) Laplace’s equation (and hence ‘easily understood’). Bruce’s views on vorticity were expressed in his 1984 paper ‘The generation and decay of vorticity’, which has had considerable impact (134 citations to date), and gives a very readable account of where vorticity comes from, and where it goes. But the topic does not loom large in his work on plumes, and for those interested in more details I recommend the mathematically rigorous monograph Vortex Dynamics by Phillip Saffman.