This paper describes an investigation of the turbulent forced plumes generated by steady release of mass, momentum and buoyancy from a source situated in an extensive region of uniform or stably stratified fluid. The treatment, which is an extension of earlier work on buoyant plumes, also brings out the relationship between the jet and the Plume as special cases of forced plumes.The analysis shows that the behaviour of a forced plume from a source of finite size which delivers buoyancy, mass and momentum can in a uniform environment be related to that from a virtual point source of buoyancy and momentum only, and a treatment is given for the latter type of forced plume. When the environment is weakly stratified it is inferred that forced plumes can be related to point definitely; but when the environment is stably stratified, increasing the release of mass and momentum from a given source of buoyancy has the effect at first of reducing the total height of the plume, and only for very large flux of momentum does the height increase again, without limit. A description is given for the behaviour of vertical jets in a stably stratified environment, and for forced plumes of fluid with negative buoyancy.

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A wide range of behaviour for turbulent forced plumes generated by vertical emission of heated or other buoyant fluid from finite sources in extensive and otherwise still uniform environments can be represented on a single non-dimensional diagram of characteristic heights, plotted against a parameter Γ, which for forced plumes represents the balance of flow conditions imposed at the physical source. The set of curves presented includes the maximum height of ascent for negatively buoyant plumes, and the height of transition from jet-like to plume-like behaviour above sources emitting buoyant fluid with excess momentum. The levels of various point and planar virtual sources are displayed also for comparison with earlier solutions. This scale diagram relates ascent and transition heights to the initial conditions at actual sources, in contrast to earlier presentations which have unduly emphasized virtual sources.A scale diagram for maximum ascent heights in stably stratified environments permits choice of the range of source conditions for a specified height of ascent and ambient stratification.

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