Selfstudy notes GAUSSIAN PLUMES Western （高斯羽毛西方Selfstudy笔记）.pdfVIP

Self-study notes - GAUSSIAN PLUMES You should read appropriate text books in order to understand the meaning of those words which are given here in italics. Consider a point source somewhere in the air where a pollutant is released at a constant rate Q (kg/s). The wind is blowing continuously in a direction x (measured in metres from the source) with a speed U (m/s). The plume spreads as it moves in the x direction such that the local concentrations C(x,y,z) (kg/m3) at any point in space form distributions which have shapes that are “Gaussian” or “normal” in planes normal to the x direction. In the lateral, or y, direction the profile shape is given by ⎛⎜ −y 2 ⎞⎟ ⎜ ⎟ 1 ⎜2 σ 2 ⎟ ⎝ y ⎠ e σ 2 π y whilst in the vertical, or z, direction it is given by ⎛ 2 ⎞ ⎜ −z ⎟ 1 ⎜⎜⎝2 σz2 ⎠⎟⎟ e σ 2 π z The parameters σ and σ (m) are the standard deviations of these Gaussian distributions, which indicate the spread y z of the plume in the y and z directions, respectively. They increase with the distance x from the source. The area under the distribution, determined by integration of the functions given above between plus an