On buoyant plumes rising from area sources in a calm environment

Low-momentum releases of buoyant material from area sources are investigated in the context of the model of Morton, Taylor & Turner (1956) (MTT). The general solution of the model equations is shown to include the case of a converging-diverging flow which we have used to model plumes from the area sources. These solutions have as asymptotes certain power solutions in terms of height, i.e. the MTT solution at large heights and a non-entraining solution near the source. The new solutions exhibit distinct and interesting flow features such as a neck (point of minimum cross-section) and a velocity peak somewhat above. The new results have been compared with the few known experimental data sources and reasonable agreement is demonstrated. In the process we have also examined the importance of the Boussinesq approximation and find results recently published not to be valid except in one special case.