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Unstable or Neutral - Crossover Between Momentum and Buoyancy

For cases with stack gas temperature greater than or equal to ambient temperature, it must be determined whether the plume rise is dominated by momentum or buoyancy. The crossover temperature difference, (DT)_c, is determined as follows:

for F_b < 55,

(DT)_c=0.0297 T_s(v_s/d_s²)^1/3      (9)

and for F_b >= 55,

(DT)_c=0.00575 T_s(v_s²/d_s)^1/3     (10)

If DT, exceeds or equals (DT)_c, plume rise is assumed to be buoyancy dominated, otherwise plume rise is assumed to be momentum dominated.

Unstable or Neutral - Buoyancy Rise

For situations where DT exceeds (DT)_c as determined above, buoyancy is assumed to dominate. The distance to final rise, x_f, is assumed to be 3.5x^*, where x^* is the distance at which atmospheric turbulence begins to dominate entrainment. The value of x_f is calculated as follows:

for F_b < 55:

x_f=49F_b^5/8      (11)

and for F_b >= 55:

x_f=119F_b^2/5     (12)

The final effective plume height, h_e (m), is determined as

for F_b < 55:

h_e=h_s+(21.425 F_b^3/4/u_s)    (13)

and for F_b = 55:

h_e=h_s+(38.71 F_b^3/5/u_s)          (14)

Unstable or Neutral - Momentum Rise

For situations where the stack gas temperature is less than or equal to the ambient air temperature, the assumption is made that the plume rise is dominated by momentum. If DT is less than (DT)_c, the assumption is also made that the plume rise is dominated by momentum. The plume height is calculated as:

h_e=h_s+3d_s(v_s/u_s)     (15)

Briggs suggests that this equation is most applicable when v_s/u_s is greater than 4.

Algorithms I - Algorithms II - Algorithms III - Algorithms IV - Algorithms V -  Algorithms VI - Algorithms VII - Algorithms VIII - Algorithms IX - Algorithms X

Air pollution map (XY-Plane) produced by continuous discharge in time (three stacks). The red colour represents high pollutant concentrations. Wind: SW (225 degrees).

Pollution map (XY-Plane) produced by continuous discharge in a road region. The fucshia squares represent the road line (position of the different point sources) in a XY-Plane. The red colour represents high pollutant concentrations.