Journal of Heat Island Institute International Vol. 12-2 (2017)

Academic Article

The Influence of building shapes to the street wind
- Using wind tunnel experiment and numerical computation Ayana Fukui*1

Xiayue Wang*2

Masakazu Moriyama*3

Hitoshi Kono*4*1 Graduate school of Science and Technology, Setsunan University*2 The former graduate student of Setsunan University
3* Professor, Faculty of Science and Engineering, Setsunan University*4 Professor emeritus at University of Hyogo
Corresponding author: Masakazu Moriyama , moriyama@led.setsunan.ac.jp

ABSTRACTIn recent years, the shape of a building using a curved surface has increased from a quadrangular prism. One
reason is to avoid the occurrence of strong winds caused by buildings. In this study, wind tunnel experiments andnumerical computations are performed, and the influence on flow is evaluated by comparing the wind velocity
distribution around the building model typified by a quadrangular prism and a circular cylinder. As a result, at thepoint behind a building, the change in the wind velocity with the height of the circular cylinder is smaller than thatof the quadrangular prism. The effect of mitigating wind environments, which seems to have a cylindrical shape, isconfirmed.
Key Words : Wind tunnel experiment, Numerical computation, Building shape, Urban canyon

canyons in building groups of prism and cylinder as fundamental

1. Introduction

research using wind tunnel experiments and numericalcomputations.

In recent years, the shape of a building using a curved surface
has increased from a quadrangular prism. This seems to include
the meaning of mitigating the strong wind. In London, the head

2. Wind tunnel experiment

office of Swiss Re is in the smooth form, is reported to have few
strong wind caused by buildings than other square building.

2.1 Method of wind tunnel experiment

In this research, the influence of flow by comparing the wind

In the experiments presented in the paper, an urban area with avelocity distribution around the building model typified by acharacteristic street configuration is considered. The street andquadrangular prism and a circular cylinder using wind tunnel

the back of the building are the main examination target position.

experiment and numerical computation is evaluated. The

As shown in Fig. 1, the wind tunnel used in the experiment has apurpose of the research is to examine the mitigation effect of thetotal length of 300 cm, a working space of 30 cm × 45 cm,

wind environment which the cylindrical shape seems to have.

and the center of the working space at 175 cm from the inlet part

The meaning of the mitigating wind environments are to reduceof wind tunnel2). The wind velocity at the upper of the boundary

the large range of wind velocity. Here, the neutral atmosphericlayer was fixed with a value of 3 m/s. As the characteristics ofstability that approximates the natural wind of the outdoors inthe street shape, the ratio of the prism case is l : h : w= 1 : 1 : 1

the flow field of a three-dimensional street is assumed, and thefor the length between the building (l), the height (h) and thevelocity at upper level is assumed about 3 m/s, which iswidth (w) . The ratio of cylinder case is r : h : w = 1 : 1 : 1 forgenerally considered to be common in Osaka, Japan.

the diameter of cylinder (r). The width of the prism and theIn past studies, wind tunnel experiments and numerical

diameter of the circular cylinder are 3 cm.

computations were performed on single building model andsimple building group model1). However, in the study presented
here, we discussed the wind velocity distribution inside street- 40 -

0.2~0.9. The wind velocity of point ③ is extremely weakerAs shown in Table 1, two kinds of experiments with prisms andcylinders in three dimensional street model are conducted. The

than ① and ②. Especially the wind velocity of ③ is weakerwind velocity at the following 3 points under the regularthan ① and ② at z/h = 0.2.

arrangement is measured. ① in the street parallel to wind2) Comparison of ①, ② and ③ of the cylinder (see Fig.2

direction, ② in the center of the intersection, ③on the leewardright)

side of the building. For the measurement of the wind velocity,

As the same as 1), the wind profile of all points ①, ② and ③

CLIMOMASTER (KANOMAX, Model 6543-21)3) is installed

are almost no differences at the height of z/h= 1.3~2.0.

in the center of the working space. Measurement is carried out

Although the difference is small, point ② is weaker than ① atadjusting to the position of points ①②③ by slightly moving

the height of z/h = 0.2~1.8. The wind velocity of point ③ isthe block model horizontally. Measurement point intervals in theextremely weaker than ① and ②.

height direction for the lower part are 0.5 cm from the bottom to3) Comparison of prism and cylinder in ① (see Fig.3 ① left)

3 cm. For the upper part from 3 cm to 6 cm, the intervals are 1

There is almost no difference between the prism and the cylinder,

cm. The sampling rate of wind velocity is 1 Hz and a

and the wind velocity increases monotonously with the height.

3-min-averaging time is used for each run.

However, the wind velocity of cylinder is slightly faster at theheight of z/h = 0.6~1.6.

2.2 Results of wind tunnel experiment4) Comparison of prism and cylinder in ② (see Fig.3 ② left)

The wind tunnel results of wind velocity with heights are shown

There is almost no difference between the prism and the cylinder,in Fig. 2, 3. U/Ur is the wind velocity ratio, and Ur is the wind

and the wind velocity increases monotonously with the height.

velocity at z/h = 2.0.

5) Comparison of prism and cylinder in ③ (see Fig.3 ③ left)

1) Comparison of ①, ② and ③ of prism (see Fig.2 left)

The wind velocity of prism is weaker a little than cylinder at theThe wind profile of all points ①, ② and ③ are almost noheight of z/h = 0.2~0.8, and the wind velocity is greatly changed

difference at the height of z/h=1.3~2. Although the difference iswhen exceeding the building height. The wind velocity withsmall, point ② is weaker than ① at the height of z/h =height of cylinder is almost same up to the building height.

Working section

PlanFig1. Wind tunnel
Table 1 Measurement points of wind tunnel experiments

Measurement points

Building model①The point in the street parallel to wind direction②The center of intersection③The point in the leeward side of the building- 41 -

Quadrangular prism（3cm×3cm×3cm）

Circular cylinder（diameter:3cm×hight:3cm）

Fig.2 Wind tunnel results of wind velocity with height (Left : prism, Right : cylinder)① The point in the street parallel to wind direction② The center of intersection③ The point in the leeward side of the building

Fig.3 Comparison of wind tunnel experiment and numerical computation (Left : wind tunnel, Right : numerical computation)- 42 -3. Numerical computation
3.1 Outline of numerical computation
The simulation is carried out using CFD software (STREAM Ver.
124)) with standard k-ε turbulence model. Boundary conditions
are given in Table 2.
1）Computation area
The computation area is 200 cm in X direction, 30 cm in Y
direction, 30 cm in Z direction. Because it is the simulation ofthe wind tunnel experiment, the Y direction and the Z direction
are set to the actual same size as the wind tunnel. The grid
spacing is 0.1 cm in the horizontal direction. It is 0.1 cm in thevertical direction from the bottom to the building height, andabove the building height an expanded grid interval is used.
Table 2

Boundary conditions
Power law
Inlet

Wind velocity:
3 m/s at height of z = 15cm
Power exponent: 1/3.7

OutletUpper surface
Bottom surface
Sides
Building surfaces

Free slip
Free slip
Logarithmic wind profile law over theFig.4 Culcuration results of wind velocity with heightsmooth surface(Upper : prism, Lower : cylinder)Free slip
Logarithmic wind profile law over the3) Comparison of prism and cylinder in ① (see Fig.3 ①)

smooth surface

The wind velocity of the cylinder is weaker until the buildingheight, and the prism and cylinder are the same if z / h = 1.2 is2）Computation caseexceeded.

The roughness of the same size as the wind tunnel case were4) Comparison of prism and cylinder in ② (see Fig.3 ②)

arranged in the computation case.

The difference between prisms and cylinders is small, but

Two cases are calculated : one is quadrangular prism (3 cm x 3

slightly cylindr is weaker than the prism.

cm x 3 cm) and the other is circular cylinder (diameter 3 cm,5) Comparison of prism and cylinder in ③ (see Fig.3 ③)

height 3 cm).

The prism changes largely in wind velocity to the height of z/h =1.0. But the wind velocity of the cylinder does not change much

3.2 Results of numerical computationin the height direction until the height of z/h = 1.0.

The numerical computation results of wind velocity with heights
are shown in Fig. 3 and 4.

As shown in the upper part of Fig. 5, the horizontal vortexes

1) Comparison of ①, ② and ③ of prism (see Fig.4)

behind the prism and cylinder do not significantly affect the flow

The wind profile of points ① and ② are making similar

between buildings in the X axis direction.

changes. However, point ② is weaker than ① at the height ofz/h = 0.3~2.0. The wind velocity of point ③ isIn comparison of prism and cylinder, the wind velocity is similar,

extremely

as shown in the lower part of Fig.5, in the street parallell to theweaker than ① and ②.

wind direction.

2) Comparison of ①, ② and ③ of the cylinder (see Fig.4)

The results of the numerical computation here is not yet steadily.

The wind profile of points ① and ② are making similar

It seems that the further discussion about the behavior of thechanges. However, point ② is weaker than ① at the height ofz/h = 0.8~2.0. The wind velocity of point ③ isvortexes behind a building is needed.

extremely

weaker than ① and ②.

- 43 -Acknowledgment4. Comparison between wind tunnel experiments andThis work was supported by JSPS KAKENHI, Grant-in-Aid fornumerical computations

Exploratory, Grant Number JP 26630267.
A comparison of the results of wind tunnel experiments andnumerical computations are given in Fig. 3.
The results of the numerical computations are similar to theresults of the wind tunnnel in vertical profile of wind velocity.
However there are the different points as below.
The wind velocity of points ① and ② decrease monotonously
to the ground level in wind tunnnel, but in the results ofnumerical computations, the change of the height direction aresmaller than wind tunnnel at z/h=1.6～2.
In the point ③, the wind velocity of the wind tunnnel is almost
constant in the vertical direction at z/h=0.2～1.6. Especially thewind velocity of the prism is almost zero at z/h=0.9. The reason
seems the vortex of the vertical section caused by street canyons(see Fig. 5）.
5. Conclusions
The rusults of wind tunnel experiments and numericalcomputations are used to compare the wind velocity distribution
around the building model typified by prisms and cylinders toevaluate the influence on flow.
As the results, the wind velocity of point ③(behind bldg.) is
extremely weaker than ① (street) and ② (intersection). In
addition, in the wind tunnel experiment of point ③, the windvelocity of prism is weaker a little than cylinder at the height ofz/h = 0.3~0.8. In further, numerical computation of point ③, thechange of the wind velocity at the prism is large, the windvelocity of the cylinders is almost constant with heigh.
From the above, with regard to the behind a building, the wind
mitigation effect of the cylinder is confirmed by wind tunnel
experiments and also numerical computations.
References
1) Architectural Institute of Japan, AIJ Benchmarks for
Validation of CFD Simulations Applied to Pedstrian Wind
Environment around Buildings, Architectural Institute of Japan,
Sptember 26, 2016
2) Kono and Kusunoki " 3D stream and vortexes in the urban
canopy layer and transport of motor vehicles exhaust gas" ,International Journal of Environment and Pollution, vol. 25, Nos.
1/2/3/4, 2005.
3)http://www.kanomax-usa.com/product/climomaster-anemomet
er-model-6501-series/4)http://www.cradle-cfd.com/images/products/EN_ProductGuid
e_A4_email.pdf,pp.4-9- 44 -YXZ

A-A’ cross section

B-B’ cross section

XFig.5 Wind vector of computation results(Left : prism, Right : cylinder)(Upper : X - Y axis cross section (z / h = 1/5), Lower : X - Z axis cross section)(Received Apr. 30, 2017, Accepted Jul. 7, 2017)- 45 -