Page 367 - Fundamentals of Air Pollution 3E

322 20. Air Pollution Modeling and Prediction

C. Unstable-Neutral Buoyancy Plume Rise
The final effective plume height H, in m, is stack height plus plume rise.
Where buoyancy dominates, the horizontal distance x f from the stack to
where the final plume rise occurs is assumed to be at 3.5x* f where x* is
the horizontal distance, in km, at which atmospheric turbulence begins to
dominate entrainment.
For unstable and neutral stability situations, and for F less than 55, H,
in m, and x (, in km, are

For F equal to or greater than 55, H and x f are

D. Stability Parameter
For stable situations, the stability parameter s is calculated by

where A0/Az is the change in potential temperature with height.

E. Stable Buoyancy Plume Rise

For stable conditions when there is wind, H and x { are

For calm conditions (i.e., no wind) the stable buoyancy rise is

Under stable conditions, the lowest value of Eq. (20- 6a) or (20-7) is usually
taken as the effective stack height.
The wind speed that yields the same rise from Eq. (20- 6a) as that from
Eq. (20-7) for calm conditions is

F. Gradual Rise—Buoyancy Conditions
Plume rise for distances closer to the source than the distance to the final
rise can be estimated from

where x is the source-to-receptor distance, km. If this height exceeds the
final effective plume height, that height should be substituted.