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to 1.5 m upwind of the model. Table 5.1 summarizes part of the results. The
percentage of ground area of the scale model covered with sand at the end of the
experiment confirms two facts:
- the percentage of sand staying on the ground of the scale model is higher when
the simulation sets z
0
=1.5 m upwind of the model than when the simulation sets z
0
at
0.02 m. This means that if the city continues to grow northwardly, then N wind
circulation will be seriously affected in the city district, as the wind will not have the
ability to remove the sand scattered on the floor of the scale model.
- G-shaped buildings are much more effective obstacles to N wind than tower-
like buildings and L-shaped buildings.
Z
0
windward of
Telheiras (m)
Tower-like
buildings
(N blocks)
L-shaped buildings
G-shaped buildings
Z
0
=0.02
0.5
4.4
14.7
Z
0
= 1.5
3.2
16.8
37.2
Difference
+2.7
+12.4
+22.5
Table 5.1.
Percentage of ground area of the scale model covered with sand
at the end of the simulation for N wind [LOP 03, p.212]
Figure 5.15.
Erosion figures experiment inside a scale model representing Telheiras city
district [LOP 03]. The figure refers to the moment when the wind direction had
attained 9.3 m/s in an undisturbed area on the “ceiling” of the wind tunnel
Figure 5.15 shows a photograph of sand distribution during an experiment
considering a roughness length of 1.5 m windward of the city district. At the
moment the photograph was taken, wind speed had increased to 9.3 m/s in an
undisturbed area on the ceiling of the wind tunnel (Figure 5.14d) [LOP 03].
Different urban fabrics react differently to wind. When looking at the “tower-
shaped” buildings in the western part of Telheiras, it is clear that ventilation is
slightly hindered by this kind of building organization, and only the southernmost
blocks originate some sheltered areas (where the sand has remained on the ground).
I- and L-shaped buildings create wind corridors, such as x on Figure 5.16, where the
