This document discusses different types of plume patterns that can occur based on environmental conditions near the ground. It describes looping, neutral, conning, fanning, and lofting plumes that are characterized by the relative positions of the environmental lapse rate and adiabatic lapse rate lines. The document also discusses methods to enhance smokestack dispersion, including making the smokestack taller to allow pollution to dilute over a longer distance before reaching the ground, increasing the exit velocity by narrowing the smokestack opening, and increasing the exit temperature for greater positive buoyancy.

1. Plume Pattern
Lecture by- Chiranjib Kundu

2. Typical types of environmental conditions characterized by different
relative positions of environmental lapse rate and adiabatic lapse
rate lines which are generally encountered in the lower atmosphere
(less than 300m above the ground level) are shown here.
Dispersion of Air pollutants
A)Looping
Plume
B)Neutral
Plume
C)Conning
plume
D)Fanning
Plume
E)Lofting

3. Super adiabatic– ELR>ALR
Sub adiabatic– ELR<ALR

4. 1. has a wavy character and occurs in super-adiabatic condition.
2. due to presence of high degree of turbulence mixing will be
maximum.
3. higher concentration near the ground may occur.
A) Looping Plume
ELR line
ALR line

5. 1. Upward vertical movement of pollutant
2. In this case ELR is equal to ALR
3. Minimum concentration of pollutants may occur near ground level
B) Neutral Plume
ELR line
ALR line

6. 1. transformation of neutral plume to conning plume due to the presence of wind
velocity greater than 32 Km/hr.
2. this may occur when cloud cover blocks the solar radiation in day time and
terrestrial by night time.
3. presence of sub-adiabatic
condition.
4. environment is slightly stable
and limited vertical mixing may
occur.
C) Conning Plume
ELR line
ALR line

7. 1. Extreme inversion condition is must to form this plume.
2. Emission can’t lift due to extremely stable environment and only
spread horizontally
3. No vertical mixing and plume ill simply extend over large distance.
D) Fanning Plume ELR line
ALR line

8. 1. strong super adiabatic condition above a surface inversion is favorable
2. Upward movement is rapid.
3. plume has minimum downward movement due to inversion below the
stack exit point.
4. minimum or no
concentration touches ground
surface.
5. Most ideal/ favorable
situation for plume
dispersion.
E) Lofting Plume
ELR line
ALR line

9. 1. presence of inversion layer above the stack exit point.
2. Super adiabatic condition is below the stack exit point.
3. pollutant can’t lift in the vertical direction due to inversion layer.
4. maximum concentration near ground
will occur due to turbulence in the
lower area.
5. Most unfavorable situation in
environment creating maximum
pollution near ground.
F) Fumigating Plume
ELR line
ALR line

10. 1. presence of inversion layer above and below the emission level, i.e. dual
inversion layer.
2. Pollutants neither go up nor go down- trapped between two inversion layer.
3. considered as bad condition for dispersion as the dispersion can’t go above a
certain height.
G) Trapping Plume
ELR line
ALR line

11. Enhancing Dispersion with Smokestacks
1. Pollution emitted from a taller stack has to travel a longer
distance to get to the ground, so it will become more diluted.
2. It may be possible for taller stacks to get above low-level
inversion layers.

12.  With a tall enough smokestack, pollution is
emitted within the inversion aloft, forming
a fanning plume that does not pollute the
area near the smokestack. If it's not tall
enough, it will fumigate the countryside.
 In case when the inversion is at the ground,
we need the smokestack tall enough to be
above the ground inversion, so that a
lofting plume is formed. Architects will
need to know the average depth of the
nocturnal radiation inversion in order to
know how tall to build the smokestack.
Tall and Short Smoke Stacks

13. The faster the smoke streams out, the more
momentum it has, and the higher it will fly before
it levels out and disperses toward the ground.
Exit Velocity

14.  Narrowing the smokestack's
opening forces the smoke out as a
faster streaming, narrower jet.
 Backpressure from the smaller
opening may reduce the efficiency
of the flow of smoke out of the
chimney, however, partially
offsetting the increasing in plume
momentum.
Methods for Increasing Exit Velocity

15.  The higher the temperature, the greater the positive buoyancy in smoke streaming
out of the smokestack.
Exit Temperature
 The smoke has to rise higher before it is adiabatically cooled to a
neutral buoyancy temperature.