IMPROVED PREDICTION OF BENDING PLUMES

Integral plume models harbor a fundamental, often significant error be cause the standard implementation of control volumes, or elements, is inconsistent with the overall geometry of the problem. The error, call ed the negative volume anomaly, occurs irregularly, being contingent o n there being strong bending and large plume diameter. When present it causes entrainment, i.e., dilution, to be overestimated. It is of pra ctical significance because dilution estimates are used to design and assess diffusers. The anomaly arises when constructed round element fa ces intersect, as they do when plume diameters are large and plume ben ding is pronounced, inadvertently generating negative volume and a fau lty integration of the governing equations. A modified control volume is proposed to correct the error, and its performance is demonstrated. Its development yields clues to other plume behavior, for example, ho w plume trajectories may respond to the asymmetrical addition of mass and its distribution in the element.