.
A statement on the estimated error and uncertainty in the numerical results.
10.9.3 Wind Climate
The wind climate is a description of the probability of experiencing certain wind speeds and directions. It can be used to determine quickly if the wind climate is benign or harsh, and if there are any strongly prevailing wind directions.
The severity of the wind climate is important because, the more severe, then the more likely that turbulence and hot gasses from high exhaust stacks will be a problem. In benign climates turbulence is unlikely to be a problem but hot gases might still be a hazard, especially if downward facing exhausts have been utilised.
An example set of wind speed / direction frequency statistics is shown in Figure
10.11. The example is for a Northern European location, and it should be noted that different geographic locations are likely to have very different wind speed and direction distributions. The entries in the table represent percentage annual duration for each wind direction and wind speed interval. In this case, the most probable wind direction is south with a total duration of 16.5%. This means that for 16.5% of the year, or 60 days, the winds will be from the southern sector.
The right hand column also shows that this is a relatively severe wind climate with the wind speed (expressed here as Beaufort number) being at Beaufort 7 or above for about 14% of the time.
Beaufort Number Wind direction (from)
N NE E SE S SW W NW Var Total
0 0+ 0+ 0+ 0+ 0+ 0+ 0+ 0+ 0.3 0.5
1 0.2 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.5 1.5
2 0.9 0.8 0.7 0.6 0.8 0.6 1.2 1.0 0.2 7.0
3 2.1 1.3 1.3 1.5 2.1 2.3 2.5 2.4 0+ 15.5
4 2.8 1.5 1.5 2.0 3.4 3.2 3.0 3.6 21.1
5 2.7 1.0 1.8 2.3 4.2 3.6 3.4 3.5 22.5
6 1.8 0.6 1.6 2.1 3.4 3.3 2.7 2.5 18.0
7 0.9 0.2 1.1 1.3 1.8 2.0 1.4 1.1 9.8
8 0.3 0.1 0.5 0.5 0.6 0.6 0.4 0.4 3.3
9 0+ 0+ 0.1 0.1 0.1 0.1 0.1 0.1 0.7
10 0+ 0+ 0+ 0+ 0+ 0+ 0.1
11 0+
12
Total 11.6 5.7 8.8 10.5 16.5 16.1 14.9 14.9 1.0 100
Figure 10.11 - Example of wind speed / direction frequency table.
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