Geoscience Reference
In-Depth Information
streets is found to be a function of wind speed. This is quite clear in simulation with
the N wind, when the E-W oriented streets proved warmer than the N-S ones. In
courtyards, PET is higher near the buildings, but lower in the middle of the
courtyard. In the area of tall buildings to the W a mosaic of PET values are recorded,
PET being higher in the “wind-shadow” parts of the buildings.
Figure 5.13. PET estimated in Telheiras on two summer nights [AND 08]: a) warm night
with light N wind; b) cooler night with moderate N wind (see color section)
GIS modeling proved to be an adequate method to estimate the microclimatic
conditions under different weather types, using only a small number of parameters
and without requiring extra local measurements Assessment of the bioclimatic
comfort in outdoor public spaces in Lisbon has been carried out in subsequent
study [OLI 07] and in ongoing research in the frame of the Urbklim project
(Climate and urban sustainability. Perception of comfort and climatic risks)
(http://www.ceg.ul.pt/urbklim/index.html). In order to validate the use of PET in
Portugal and to assess comfort perception, questionnaires were carried out
simultaneously with weather measurement in several Lisbon green spaces .
5.8.2. Wind tunnel experiments to detect main trajectories of prevailing winds
Physical scale models permit the simulation of different meteorological
parameters within controlled conditions. Kanda synthesized the advantages and the
limitations of scale models [KAN 06].
A scale model of Telheiras (1:500) was built (Figure 5.14a and b) in the
Portuguese National Laboratory of Civil Engineering (LNEC) in Lisbon for the
study of wind speed and direction in this district of Lisbon. Several experiments
were carried out during 1 month [LOP 03; LOP SUB]. The objectives were twofold:
i) to study the airflow around the buildings and inside squares and inner courtyards;
ii) to verify how the increasing roughness due to city growth in the windward side of
the city would modify wind conditions in Telheiras district. In the aerodynamic
wind tunnel an artificial air current is created (Figure 5.14c) in an open circuit
aspiration tunnel with a 2 m × 3 m section, 10 m long. Wind speed inside the tunnel
may be adjusted up to 18 m/s. The simulation of vorticity and roughness may be
achieved through the use of different “separation elements” inserted in the tunnel
(wooden blocks of different forms, dimension and space in between) windward from
the scale model (Figure 5.14c). Several experiments were carried out for the three
Search WWH ::




Custom Search