Content uploaded by Journal of Environmental Studies
Author content
All content in this area was uploaded by Journal of Environmental Studies on Jul 25, 2022
Content may be subject to copyright.
Journal of Environmental Studies
Vol. 48, No. 1, Spring 2022
Journal Homepage: www.Jes.ut.ac.ir
Print ISSN: 1025-8620 Online ISSN 2345-6922
The Relationship Between the Placement of Building Blocks and Wind
Flow at the Pedestrian Level
Mahsa Samadpour Shahrak1, Mehrdad Karimimoshaver1*
1 Department of Architecture, Faculty of Art and Architecture, Bu-Ali Sina University,
Hamedan, Iran
DOI: 10.22059/JES.2022.331141.1008229
Document Type
Research Paper
Received
September 23, 2021
Accepted
May 27, 2021
Abstract
Assessing human comfort outdoors is one of the key criteria in the design of building. One of the
effective factors in creating comfort conditions is wind flow. The purpose of this study is to
investigate the effect of urban blocks on wind flow for creating the comfortable condition. The ratio of
buildings height to distance (H/W) and the orientation of buildings as the most important factors
affecting wind flow were examined. The ratios of 0.5, 1, 1.5, and 2 were selected and orientations of
135° to 200° were examined. A residential complex in Tabriz was selected as a case study and weather
information of the last 19 years (2002-2021) of Tabriz was extracted from the Meteorological
Organization. Months of the year that were unfavorable in terms of comfort conditions were identified
by using the Penwarden standard. Accordingly, January 6, 2021, was selected as one of the coldest
days of the year, and to simulate different scenarios, Envi-met (4.4.5) software was used. The results
show that the H/W ratios of 0.5 to 1 and the orientations of 200° to 185° and 135° are the most
appropriate. In this research two important factors, H/W and their orientation were studied in a linear
form. One of the limitations of the research is that only the comfort conditions in the outdoor
environment of the buildings have been studied. Therefore, in future research, the arrangement of
urban blocks to consume less energy inside buildings can be examined.
Keywords: Outdoor thermal comfort, wind speed, building orientation, H/W ratio
* Corresponding Author: Email: mkmoshaver@basu.ac.ir
Journal of Environmental Studies
Vol. 48, No. 1, Spring 2022
16
Introduction
Among the various factors of environmental comfort in outdoor space, wind flow has a great impact
on the quality of urban spaces. In the 1970s, Lawson et al. reported the death of two elderly women
due to sudden, strong winds around buildings. Wise et al. have conducted studies on shops that do not
have customers due to wind conditions in the area. Various researches have been done on the shape
and form of blocks, their ratio of height to their distance (H/W), orientations, and the effect of these
factors on wind speed. However, most of this research has been done in areas with warm climates and
cannot be generalized to other regions with different climates, and in most studies, the summer season
has been analyzed and studied. A limited number of studies have examined the cold days of the year
and cold climate. This research, in line with the research done in this field and with a more
comprehensive look at the relationship between H/W ratio and also examining the orientation of
buildings with more accurate angles, in the form of linear buildings, examines outdoor thermal
comfort. This research has been done around one of the residential blocks in Tabriz, Iran with a dry
climate and relatively hot summers and cold winters.
Materials and Methods
The study site is located in a residential area of Tabriz city. Tabriz (38.12°N, 46.24°E) is a metropolis
in the Azerbaijan region of Iran and is the capital of East Azerbaijan Province. Tabriz has a population
of over 1.7 million (2016). Its climate is dry steppe and enjoys a mild and fine climate in spring, a dry
and semi-hot in summer, a humid and rainy in autumn, and snowy cold in winter. The prevailing wind
is from east to west. The average annual temperature is 12.6°C (54.7 °F). It's elevation ranges between
1,350 and 1,600 meters (4,430 and 5,250 ft) above sea level.
One of the pioneers who prepared a graph to predict pedestrians' outdoor comfort zone is Penwarden.
In 1975, he introduced his graph according to his comprehensive field studies in the UK. This graph
that had been used for several years shows the needed periods for sunshine, shade, and wind according
to the metabolic rate of the pedestrian with suitable seasonal clothes. For this reason, in this study, the
Penwarden index was used to identify months of the year when conditions are unfavorable for
pedestrians. Thus, January was identified as the worst month of the year in terms of thermal comfort.
Also, February and December do not have favorable conditions. As a result, January 6, 2021, was
selected as one of the coldest days of the year, and the effect of building blocks on wind flow in winter
was investigated (Fig1).
Figure 1: Status of different months of the year in Penward index, right: shadow, left: sunny
The Relationship Between the Placement of ...
Mahsa Samadpour Shahrak, Mehrdad Karimimoshaver
17
ENVI-met software (4.4.5) was used to simulate the surrounding environmental conditions. The
information entered in the software can be seen in Table 1.
Table 1: Information and data entered in ENVI-met software
Discussion of Results:
The comparison between the H/W ratio and wind speed shows that with increasing height above
ground level and this ratio, wind speed also increases.
The results show that in winter, with increasing the H/W ratio, the wind speed also increases. The
average of wind speed at the ratios H/W=0.5 and H/W=1 is close to each other and increases when this
ratio changes to H/W=1.5 and H/W=2. Therefore, H/W=0.5 to 1 ratio is suitable for design in this
climate, and increasing this ratio can disrupt outdoor comfort conditions. This study agrees with
researches that have examined this ratio in different climates in winter.
Also about the orientation of the blocks, Oke, Jin et al. concluded that in the linear pattern the angle
between the wind direction and the axes of the blocks are inversely related to the wind speed. As the
angle between the wind direction and the axes of blocks increases, the wind speed decreases. Studies
in the subtropical climate of Tunisia's Mediterranean climate in summer, the Brazilian subtropical
climate, the temperate climate of the Netherlands in summer, the very cold climate of China
considered North-South (NS) orientation as the most appropriate one. Rizk-Hegazy et al. compare the
four directions of 70,160,100,10 degrees from the north in the hot and dry climate of Saudi Arabia and
consider 160 degrees clockwise from the north as the most suitable option. Also, studies conducted in
the hot and dry climate of Algeria, hot and humid climate of Brazil are considered northeast-
southwest(NE-SW), Northwest-Southeast (NW-SE) as the best orientation. This study, which
examines eight angles, shows that the angles of 200° to 185° and 135° have a lower average wind
speed, so it creates favorable conditions at the site, and angles of 175°, 165°, 155°, and 145° have
higher average wind speeds and cause unfavorable conditions in the environment.
Conclusions:
The present study evaluates wind speed as the most important factor affecting thermal comfort
conditions around residential blocks in a linear manner. Assuming that the height, distance, and
orientation of the blocks are the factors that can affect wind speed. In this study, an arid climate with
relatively hot summers and cold winters was selected as the study area. By using the Penwarden index,
and comparing temperature and wind speed, the months of the year with the worst comfort conditions
were identified. January was selected as the month that needs to be studied more closely to improve
environmental conditions. Examining the number of changes that occur in the average wind speed in
changing the H/W ratio, it can be concluded that with increasing H/W ratio, the average wind speed
has an upward trend. And, ratios of H/W=0.5 to 1 can be considered the most appropriate ratio.
Concerning the orientation of the buildings, it shows that the average wind speed was the lowest at an
Information entered in ENVI-met
46.24°E, 38.12°N
Geographical Location
Tabriz, East Azerbaijan Province, Iran
Name of the area
2021.01.06
Date
x-Grids=50, y-Grids=50, z-Grids=40
Model Dimensions
dx=4,dy=4,dz=5
Size of grid cell in meter
9 AM-8 PM, 11hours
Simulation time
Min: -9°c, Max: 0.6°c
Temperature
2.9m/s
Wind speed
70°(North-East)
Wind direction
58%
Relative humidity
Albedo: 0.4, Thermal capacity: 2.08 [J m−3 K−1] × 106,
Thermal Conductivity: 1.63 [W m−1 K−1]
Pavement material: Cement Concrete
Thickness: 15cm, U-value: 2.54 (W/ m2K)
Building envelope: Cement Walls
Journal of Environmental Studies
Vol. 48, No. 1, Spring 2022
18
angle of 200°, and with the change of the direction of the buildings clockwise to the north, the average
of this index increased and reached the highest value at an angle of 165° then it decreases. Therefore,
angles of 200° to 185° and 135° are the most favorable, and angles of 175° to 145° are not suitable. In
this research two important factors, H/W and their orientation were studied in a linear form. One of the
limitations of the research is that only the comfort conditions in the outdoor environment of the
buildings have been studied. Therefore, in future research, the arrangement of urban blocks to
consume less energy inside buildings can be examined.
–
(H/W)
°°
H/W
°°°
H/W
LawsonPenwarden
Wise
Karimimoshaver
Metje
Müller
mkmoshaver@basu.ac.ir Email:
DOI: 10.22059/JES.2022.331141.1008229
DOR: 20.1001.1.10258620.1401.48.1.2.5
Kim
(Hegazy and Qurnfulah, 2020)
Achour-YounsiKharrat
H/W
HegazyQurnfulah
Shui
Liu
Lin
Masnavi
Javanroodi
Nasrollahi
EyniTaban
RozatiGhanbaran
Karimimoshaver
(H/W)
°°
¸¸
WRPLOT
Lakes Environmental
WRPLOT
WRPLOT
Station Elevation
Lon
Lat
Station ID
Data Fields (2002-2021)
E
N
Farsicad.com
Ashrae, 1997
Penwarden and Wise, 1975
(0.5 clo)
(1.0 clo)
(1.5 clo)
(Taleghani et al., 2015
u/t+ui(u/xi)=-p’/x+Km(2u/x2i)+ f(v –
vg)- Su
v/t+ ui(u/xi)=-p’/y+Km(2v/x2i)+ f(u –
ug)- Sv
w/t+ ui(w /xi)=-p’/z +Km(2 w /x2i)+
g (Ɵ (z) / - Ɵref(z))- S w
f ( = 104
'pƟ
ZƟref
p
W
u
x
v
y
w
z
0
(ui= u,v,w i=1,2,3)Su,
Sv , Sw
Wang
and Akbari, 2016; Taleghani and Berardi, 2018
ampm
°N°E
Tabriz, East Azerbaijan Province, Iran
x-Grids=, y-Grids=, z-Grids=
dx=,dy=,dz=
°c
°c
°c
]
1−
K
3−
m [J 2.08 capacity: Thermal 0.4, Albedo: ]
1−
K
1−
m [W 1.63 Conductivity: Thermal ,
6
10 ×
K)
2
m (W/ 2.54 value:-U 15cm, Thickness:
Kasmaei
H/W
H/W
H/W
H/W=0.5
H/W=2
H/W=0.5H/W=1
H/W=1.5H/W=2
H/W
H/W
H/W=0.5,1
(Johansson et al., 2006)
(Martinelli and Matzarakis, 2017)
H/W
Jamei
and Rajagopalan, 2017Nasrollahi et)
(al., 2017H/W
°°
°°
°
°
°
°
°
°°
°°
°°
°°
°°
°
OkeJin
Oke, 1988, Jin et al, 2017
(E-W)(N-S)
(NE-SW)NW-)
(SE
Achour- Younsi and Kharrat, 2016, )
Martins et al., 2012, Nasrollahi et al., 2017,
(Taleghani et al., 2015, Hegazy and Qurnfulah, 2020
Achour-Younsi and)
(Kharrat, 2016Martins et)
(al., 2012
(Taleghani et al., 2015)
(Liu et al., 2019)(N-S)
HegazyQurnfulah
(Lin et al., 2019)
(NW-SE)Nasrollahi
°°
°°
°°
°°
H/W
H/W
°
°°°
°
°°°
1 Height to Width
2 WCET (Wind Chill Equivalent Temperature)
3 Navier–Stokes
4 Boussinesq–Approximation
Achour-Younsi, S., & Kharrat, F. (2016). Outdoor thermal comfort: impact of the geometry of an
urban street canyon in a Mediterranean subtropical climate–case study Tunis, Tunisia.
Procedia-Social and Behavioral Sciences, 216, 689-700.
Ashrae, A.H.-F., 1997. American Society of Heating, Refrigerating and Air- Conditioning Engineers.
Inc. Atlanta.
Eyni, A., & Taban, M. (2019). Evaluation of the effect of physical structure on the wind flow pattern
in urban environments (case study: Siyah-Poshan and Gozare Shahi neighborhoods in Ghaleh
district of Dezful). Environmental Sciences, 17(2), 155-172.
Hegazy, I. R., & Qurnfulah, E. M. (2020). Thermal comfort of urban spaces using simulation tools
exploring street orientation influence of on the outdoor thermal comfort: a case study of Jeddah,
Saudi Arabia. International Journal of Low-Carbon Technologies, 15(4), 594-606.
Jamei, E., & Rajagopalan, P. (2017). Urban development and pedestrian thermal comfort in
Melbourne. Solar Energy, 144, 681-698.
Javanroodi, K., Mahdavinejad, M., & Nik, V. M. (2018). Impacts of urban morphology on reducing
cooling load and increasing ventilation potential in hot-arid climate. Applied energy, 231, 714-
746.
Jin, H., Liu, Z., Jin, Y., Kang, J., & Liu, J. (2017). The effects of residential area building layout on
outdoor wind environment at the pedestrian level in severe cold regions of China. Sustainability,
9(12), 2310.
Johansson, E. (2006). Influence of urban geometry on outdoor thermal comfort in a hot dry climate: A
study in Fez, Morocco. Building and environment, 41(10), 1326-1338.
Karimimoshaver, M., Hajivaliei, H., Shokri, M., Khalesro, S., Aram, F., & Shamshirband, S. (2020).
A model for locating tall buildings through a visual analysis approach. Applied Sciences,
10(17), 6072.
Karimimoshaver, M., & Shahrak, M. (2022). The effect of height and orientation of buildings on
thermal comfort. Sustainable Cities And Society, 79, 103720. doi: 10.1016/j.scs.2022.103720
Karimimoshaver, M., Khalvandi, R., & Khalvandi, M. (2021). The effect of urban morphology on heat
accumulation in urban street canyons and mitigation approach. Sustainable Cities And Society,
73, 103127. doi: 10.1016/j.scs.2021.103127
Kasmaei, M. (2003), Climate and architecture, Khak
Kim, H., Lee, K., & Kim, T. (2018). Investigation of pedestrian comfort with wind chill during winter.
Sustainability, 10(1), 274.
Lawson, T. V., & Penwarden, A. D. (1975). The effects of wind on people in the vicinity of buildings.
4th Int. In Conf. Wind Effects on Buildings and Structures, Heathrow.
Lin, Y., Jin, Y., & Jin, H. (2019). Field study on the microclimate of public spaces in traditional
residential areas in a severe cold region of China. International journal of environmental
research and public health, 16(16), 2986.
Liu, Z., Jin, Y., & Jin, H. (2019). The effects of different space forms in residential areas on outdoor
thermal comfort in severe cold regions of China. International journal of environmental
research and public health, 16(20), 3960.
Martinelli, L., & Matzarakis, A. (2017). Influence of height/width proportions on the thermal comfort
of courtyard typology for Italian climate zones. Sustainable Cities and Society, 29, 97-106.
Martins, T. A. T. H. I. A. N. E., Adolphe, L., & Krause, C. L. Á. U. D. I. A. (2012, November).
Microclimate effects of urban geometry on outdoor thermal comfort in the Brazilian tropical
semi-arid climate. In Conference opportunities, limits e needs towards and environmentally
responsible architecture.
Masnavi, M. R., Laghai, H. A., & Ghobadi, N. (2012). Eco design and the optimization of passive
cooling ventilation for energy saving in the buildings: a framework for prediction of wind
environment and natural ventilation in different neighborhood patterns. In Design for innovative
value towards a sustainable society (pp. 177-182). Springer, Dordrecht.
Metje, N., Sterling, M., & Baker, C. J. (2008). Pedestrian comfort using clothing values and body
temperatures. Journal of Wind Engineering and Industrial Aerodynamics, 96(4), 412-435.
Müller, N., Kuttler, W., & Barlag, A. B. (2014). Counteracting urban climate change: adaptation
measures and their effect on thermal comfort. Theoretical and applied climatology, 115(1), 243-
257.
Nasrollahi, N., Hatami, M., Khastar, S. R., & Taleghani, M. (2017). Numerical evaluation of thermal
comfort in traditional courtyards to develop new microclimate design in a hot and dry climate.
Sustainable Cities and Society, 35, 449-467.
Oke, T. R. (1988). Street design and urban canopy layer climate. Energy and buildings, 11(1-3), 103-
113.
Penwarden, A. D., & Wise, A. F. E. (1975). Wind environment around buildings. HM Stationery
Office.
Rozati, S. H., & Ghanbaran, A. (2014). Comfort Evaluation in Urban Open Spaces Based on Wind
Comfort Criteria, Case Study: Isfahan. Environmental Sciences, 12(4).
Shui, T., Liu, J., Yuan, Q., Qu, Y., Jin, H., Cao, J., & Chen, X. (2018). Assessment of pedestrian-level
wind conditions in severe cold regions of China. Building and environment, 135, 53-67.
Taleghani, M., & Berardi, U. (2018). The effect of pavement characteristics on pedestrians’ thermal
comfort in Toronto. Urban climate, 24, 449-459.
Taleghani, M., Kleerekoper, L., Tenpierik, M., & Van Den Dobbelsteen, A. (2015). Outdoor thermal
comfort within five different urban forms in the Netherlands. Building and environment, 83, 65-
78.
Wang, Y., & Akbari, H. (2016). The effects of street tree planting on Urban Heat Island mitigation in
Montreal. Sustainable Cities and Society, 27, 122-128.
Wise, A. F. E. (1971). Effects due to groups of buildings. Philosophical Transactions of the Royal
Society of London. Series A, Mathematical and Physical Sciences, 269(1199), 469-485.