Review of Japanese Urban Models and a Scale Model Experiment - Meteorological and Air Quality Models for Urban Areas - page 33

(b)

(a)

Fig. 5.1 Examples of CFD application to realistic urban geometries. (a) Contour map of instanta-
neous surface wind in Sinjuku (from Kanda, 2006c), and (b) contour map of instantaneous surface
temperature field and surface wind vector at a coastal area in Tokyo (from Ashie et al., 2005). The
area is 500 m × 500 m for (a) and (b) (See also Colour Plate 7 on page 174)

Kono 2006; Kanda, 2006c; Yamada, 2006). Calculation of multi-reflective radiation
processes within real urban canopies requires tremendous computational loads, and
LES require unrealistic quasi-cyclic conditions for lateral boundaries.

5.2 Scale Model Experiments

5.2.1 Brief Review of Reduced Scale Model Experiments
for Urban Climate

In real cities, field data acquired using towers, aircrafts, and satellites yield a range of
valuable information but have not yet resulted in a comprehensive understanding of
the complex physics involved in the urban meteorology. Most of the difficulties arise
from the heterogeneity and diversity in cities. Reduced-scale physical models pro-
vide an alternative and powerful method to study urban climates, free of site-specific
diversities, although such models are often highly simplified. Indoor experiments
that use arrays of urban-like flow obstacles or roughness elements including cubes,
blocks, and cylinders have already contributed to the understanding of neutral-flow
structures (see review Kanda, 2006b). Outdoor experiments are a promising way
to systematically investigate relations between surface structures and physical pro-
cesses within and above the roughness sublayer (RSL) under realistic synoptic con-
ditions. Results from such models can be used to detect the physical parameters
needed to construct numerical models. Pioneering outdoor experiments using large-
scale obstacles (e.g., ~1 m) such as MUST (Yee et al., 2004) and Kit FOX (Hanna
and Chang, 2001) focused on dispersion processes and did not consider energy bal-
ance. Pearlmutter et al. (2005) evaluated urban surface energy fluxes using an open-
air scale model.