1.1.5.2

Lateral and VerticalVirtual Distances.The equations in Tables 1‑1 through 1‑4 define the dispersion parameters for an ideal point source. However, volume sources have initial lateral and vertical dimensions. Also, as discussed below, building wake effects can enhance the initial growth of stack plumes. In these cases, lateral (x

_{y}) and vertical (x_{z}) virtual distances are added by the ISC models to the actual downwind distance x for the σ_{y}and σ_{z}calculations. The lateral virtual distancein kilometersfor the rural mode is given by:where the stability‑dependent coefficients p and q are given in Table 1‑5 and σ

_{yo}is the standard deviation in meters of the lateral concentration distribution at the source. Similarly, the vertical virtual distance in kilometers for the rural mode is given by:where the coefficients a and b are obtained form Table 1‑2 and σ

_{zo}is the standard deviation in meters of the vertical concentration distribution at the source. It is important to note that the ISC model programs check to ensure that the x_{z}used to calculate σ_{z}at (x + x_{z}) in the rural mode is the x_{z}calculated using the coefficients a and b that correspond to the distance category specified by the quantity (x + x_{z}).

To determine virtual distances for the urban mode, the functions displayed in Tables 1‑3 and 1‑4 are solved for x. The solutions are quadratic formulas for the lateral virtual distances; and for vertical virtual distances the solutions are cubic equations for stability classes A and B, a linear equation for stability class C, and quadratic equations for stability classes D, E, and F. The cubic equations are solved by iteration using Newton's method.

1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 - 26 - 27 - 28 - 29 - 30 - 31 - 32 - 33 - 34 - 35 - 36 - 37 - 38 - 39 - 40 - 41 - 42 - 43 - 44 - 45 - 46 - 47 - 48 - 49 - 50

APLICACIONES castellano: DIS CUS DES RAD english: DIS CUS DES RAD

português: DIS CUS DES RAD italiano: DIS CUS DES RAD