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DISPER software: Air pollution map produced by three different stacks (XZ-plane)
Canarina software for analysis of air pollution in environment: air pollution control, environmental engineering, environmental consultancy service, environment simulation, environmental modeling and environmental impact assessment. Air dispersion software: ISC 89 diffusion
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DISPER: Air pollution dispersion ˇ DISPER - Solutions - Data - Algorithms - Emissions - Graphs - ISC3 (VOL. 2)
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In
Equation (1-65), the integral in the longitudinal (i.e., upwind or x) direction
is approximated using numerical methods based on Press, et al
(1986). Specifically, the ISCST model
estimates the value of the integral, I, as a weighted average of previous
estimates, using a scaled down extrapolation as follows:
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where the integral term refers to the integral of the plume function in
the upwind direction, and IN and I2N refer to successive
estimates of the integral using a trapezoidal approximation with N intervals
and 2N intervals. The number of
intervals is doubled on successive trapezoidal estimates of the integral. The ISCST model also performs a Romberg
integration by treating the sequence Ik as a polynomial in k. The Romberg integration technique is
described in detail in Section 4.3 of Press, et al (1986). The ISCST model uses a set of three criteria
to determine whether the process of integrating in the upwind direction has
"converged." The calculation
process will be considered to have converged, and the most recent estimate of
the integral used, if any of the following conditions is true:
1) if
the number of "halving intervals" (N) in the trapezoidal
approximation of the integral has reached 10, where the number of individual
elements in the approximation is given by 1 + 2N-1 = 513 for N of
10;
2) if
the extrapolated estimate of the real integral (Romberg approximation) has
converged to within a tolerance of 0.0001 (i.e., 0.01 percent), and at least 4
halving intervals have been completed; or
3) if
the extrapolated estimate of the real integral is less than 1.0E-10, and at
least 4 halving intervals have been completed.
