Momentum-based solutions for buoyant jet trajectories in still and flowing ambient fluids

A perturbation analysis based on the relevant components of momentum is employed to locate the two-dimensional centreline trajectories of buoyant jets in still and flowing ambient fluids. The use of this approach is conceptually different from a traditional analysis, commonly found in Eulerian integral models, which makes use of the relevant components of the centreline velocity for locating discharges. Comparisons with available data indicate that the momentum based trajectory equations can accurately predict the flow trajectories and are in good agreement with the trajectory predictions from a Lagrangian integral model - JETLAG. Lagrangian models, such as JETLAG, employ a cross-sectional average velocity to locate the flow trajectory and this is equivalent to the momentum based method described here.