CROSS-SECTIONAL ASYMMETRY OF PLUMES IN INVERSION CONDITIONS

Pollution emitted from a tall stack forms a plume, whose shape is determined largely by the prevailing meteorological conditions. If the plume encounters an inversion and its rise is thus restricted, the phenomenon of 'fanning' is often observed to result. Three models for calculating the cross-sectional shape of a plume under inversion conditions are derived and compared. Two of the models deduce an elliptical shape with an increased width (i.e. in the horizontal direction). The third permits only vertical 'squashing' of the plume which results in increased pollutant concentrations. Accurate knowledge of this shape is highly desirable in many instances (e.g. plume impingement on hillsides, washout and rainout) so that ground level concentrations can be kept to a minimum under all possible meteorological conditions. © 1979 IPC Business Press Ltd.