Wind Distribution
in Doushi Garden Site
Yi
Jiang, Ph.D. Student
Building
Technology Program, MIT
In
Doushi Garden site, there are over 10 highrise buildings. The lowest
one is 33 meters high, and the highest one 90 meters. Since Beijing
is windy in winter and spring, in such a highrise building area,
the investigation studies if the preliminary City Garden design
would cause discomfort in the site.
Determination
of the Incoming Wind
In
a typical year, there are 9 days during which the wind speed is
higher than 7.6 m/s (17 mph) in Beijing (1997 ASHRAE Fundamentals
Handbook, 26.30). So we set the incoming wind speed to be 7.6 m/s
at the height of 10 meters. The incoming wind profile is
U = c z^{1/4}
where U is the mean wind speed,
z is the height of the wind, and c is a constant.
Calculation
Results
We
plan to calculate four cases, in which the wind is from north, south,
east and west directions respectively. Two cases with the wind from
the north and the west are reported here.
For the wind from the north:
Fig. 1 (3 Dimensional) and
Fig. 2 (2 Dimensional) show the wind velocity distribution at the
height of 1.5 meters above the ground to evaluate pedestrian’s
comfort.
Fig. 3 shows the wind speed
distribution at section 11.
Fig. 4 shows the wind speed
distribution at section 22.
Fig. 5 shows the wind velocity
distribution at the height of 30 meters above the ground. Since
the heights of all buildings are above 30 meters, we would like
to find the wind speed at that height.
Fig. 6 shows the wind velocity
distribution at the height of 70 meters above the ground. There
are 8 buildings whose heights are above 70 meters.
For the wind from the west:
Fig. 7 (3 Dimensional) and
Fig. 8 (2 Dimensional) show the wind velocity distribution at the
height of 1.5 meters above the ground to evaluate pedestrian’s
comfort.
Preliminary
Analysis
Our
preliminary calculations found that the current design can cause
serious discomfort problems.
(1)
The wind speed at section 1 and 2 may reach 8 ~ 9m/s that
is well above the comfort limit (5 m/s)
(2)
Although the wind speed at the community area is not very
high for the north wind, the high wind speed will occur when the
wind is from the west due to the bell arrangement of the buildings.
(3)
At the height of 30 meters, the wind speeds
in the most buildings are 9~10 m/s. At the height of 70 meters,
the wind speed above 12 m/s.
Fig. 1 Wind velocity
distribution at the height of 1.5 meters (3D) above the ground.
Fig. 2
Wind velocity distribution at the height of 1.5 meters (2D) above
the ground.
Fig.
3 The wind speed distribution at section 11.
Fig.
4 The wind speed distribution at section 22.
Fig.
5 The wind velocity distribution at the height of 30 meters above
the ground.
Fig. 6 The wind velocity distribution at
the height of 70 meters above the ground.
Fig. 7 Wind velocity
distribution at the height of 1.5 meters (3D) above the ground.
Fig. 8 Wind velocity distribution at the
height of 1.5 meters (2D) above the ground.
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