For diffusion analysis, diffusion parameters in lateral and vertical directions are essential, so their values usually need to be obtained. In the most popular Gaussian type concentration formula, the value of the lateral diffusion parameter σ
Y is relatively easy to obtain both in the wind tunnel and the atmospheric experiments. On the other hand, the vertical concentration distribution is not simple owing to the effect of shear in the turbulent boundary layer, so it is not so easy to decide the value of the vertical diffusion parameter σ
Z even in wind tunnel diffusion experiments.
In this paper, one graphical method for obtaining the vertical diffusion parameter σ
Z is described in detail using the wind tunnel diffusion data. The method is as follows. When several suitable curves of the nondimensional Gaussian type concentration formula are superposed one by one on the measured vertical concentration profile, the best-fit curve can be chosen. The value of parameter σ
Z can be calculated from the values of parameters of the chosen curve, and σ
Z can be obtained with the same order accuracy as that of the values of concentration.
Originally, this simple but practical method for diffusion analysis was briefly described by Sakagami (1965).
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