A Idris

B P Huynh

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COMPUTATIONAL STUDY OF SINGLE-SIDED VENTILATION THROUGH A 3-
DIMENSIONAL ROOM WITH ROUNDED EDGES 
 
 
A. Idris 
Department of Mechanical Engineering 
Universiti Kuala Lumpur  
Malaysian Spanish Institute 
Kulim Hi-Tech Park, 09000 Kulim, Kedah 
Malaysia 
 
B.P. Huynh 
Faculty of Mechanical Engineering & IT 
University of Technology, Sydney 
Sydney, NSW, Australia 
 
 
 
 
 
ABSTRACT 
A commercial Computational Fluid Dynamics (CFD) 
software package is used to investigate numerically a 3-
dimensional rectangular-box room with rounded edges. The 
room has all its window openings located on one wall only. The 
standard K–ε turbulence model is used. Air's flow rate and flow 
pattern are considered in terms of wind speed and the openings' 
characteristics, such as their number, location, size and shape. 
Especially, comparison with ventilation rate corresponding to 
when the room edges are sharp is made; and thereby the effects 
of the edges being rounded are examined.  
 
INTRODUCTION 
Natural ventilation is created by pressure differences 
between the inside and outside of building induced by wind and 
air temperature differences, and it has been widely recognized 
as one way towards achieving low-energy building and clean 
environment. Air exchange is necessary to remove stale air and 
odours, dilute the product of combustion and respiration, 
remove harmful chemicals, and combat excess heat. Effective 
ventilation in a building will affects the occupant health and 
productivity. 
In achieving optimum efficiency of natural ventilation, the 
building design should start from the climatic conditions and 
orography of the construction to ensure the building 
permeability to the outside airflow to absorb heat from indoors 
to reduce temperatures. In the United State, large and thick 
building shapes, fire codes, security requirements and privacy 
concerns  often prevent design of cross ventilations eventhough 
the single-sided ventilation has fewer adaptive comfort hours 
than cross ventilation and much less ventilation volume [1]. 
In temperate climates, depending on local variations, 
design and occupational patterns, roughly 50 percent of total 
energy use for a typical building is used for indoor air 
conditioning, in term of cooling and heating[2]. According to 
Linden, the energy used in building corresponds to a significant 
proportion of total energy consumption, particularly in 
countries where the proportion of air-conditioned building is 
large. In the US, about 30% of total energy consumption is used 
in non-domestic buildings, and of that fraction about 30% is 
used in heating and cooling [3]. A study conducted in Sydney 
showed a reduction of 25 – 33% in naturally ventilated mixed 
mode buildings and high occupant comfort satisfaction 
score[4]. In OECD countries, the building sectors’ share of total 
energy consumption remains between 25% and 40% [5]. 
Most of the buildings in urban area are ventilated with 
single-sided ventilation only. Single-sided ventilation occurs 
when the building communicates with the outdoor environment 
through one or more openings located on the same exterior 
wall. Effective ventilation is important for buildings: houses, 
shelters, mobile homes, warehouses, greenhouses, etc. There 
are two major natural ventilation types: cross and single-sided 
ventilation. In both cases, air is driven in/out of the building 
due to pressure differences across the openings, which result 
from the combined action of wind and buoyancy driven forces. 
The physical processes are very complex and the interpretation 
of their role in ventilation effectiveness is a difficult task. 
Mathematical interpolation of the physical phenomena related 
to this type of ventilation has so far been handled by empirical 
and simulation models. Computational Fluid dynamic (CFD) 
has proven to be a powerful tool for the prediction of air flow 
and related variables distribution, thus helping the design and 
Proceedings of the ASME 2013 International Mechanical Engineering Congress and Exposition 
IMECE2013 
November 15-21, 2013, San Diego, California, USA 
IMECE2013-65843
1 Copyright © 2013 by ASME
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evaluation of HVAC and fire emergency systems under a wide 
range of scenarios[6].  
NOMENCLATURE 
Uj (j=1-3) – component of average velocity vector
g-the gravity acceleration 
µt- turbulent viscosity 
Cµ- empirical constant 
K-turbulent kinetic energy 
ε- dissipation rate 
ĸ- Von Karman’s constant 
Uave- the average flow velocity 
Ti –turbulence intensity 
L- length scale 
 
METHODOLOGY  
a. Problem description 
 When dealing with wind driven natural ventilation, two 
different ventilation patterns can be identified, namely cross 
ventilation and single-sided ventilation. The fi
characterized by the presence of two or more openings on 
opposite sides of the building, and it can provide ventilation 
rates larger than those obtained by single
where the openings are located on a single
there are situations wherein single-sided ventilation is the only 
option. This occurs, for example, with buildings which have 
only one side exposed to the wind. Thus 
ventilation is investigated in the present study
cases are considered: 
• Case 1: Leeward ventilation with an opening on the
of sharps edges (a) and rounded edges (b).
• Case 2: Left-side ventilation with double opening on the 
walls of sharps edges (a) and rounded edges (b).
• Case 3: Top ventilation with an opening on the
sharps edges (a) and rounded edges (b). 
• Case 4: Windward ventilation with an opening on
of sharps edges (a) and rounded edges (b).
• Case 5: Cross ventilation of sharps edges (a) and rounded 
edges (b). 
 
 In this work, the intention is focused on computational 
study on single-sided wind driven ventilation. In order to 
perform the simulations, a building-like model, whose 
dimensions are 5 m x 5 m x 5 m. Ten different building
are used: the difference among five models is the location of 
the openings, which have the same total area of 4 m
shows a schematic view of the building mod
openings used in this work. Furthermore, a log
profile upwind of the building is employed. 
domain is sufficiently large to avoid disturbance of air flow 
around the building as shown in Figure 2. 
 
b. Computational method 
 The commercial software package CFD-
group is used for the computation. It is based
 
rst one is 
the 
-sided ventilation 
 facade. However, 
single-sided 
. Five different 
 walls 
 
 
 walls of 
 the walls 
 
 models 
2
. Figure 1 
el with different 
arithmic wind 
The computational 
ACE from the ESI 
 on the numerical 
solution of the governing equati
and Navier-Stokes equations
The package employs the Finite Volume Method to solve 
iteratively the couple system of governing equations for the 
three mean velocity components and pressure, plus K and ε, 
until satisfactory convergence 
been reached.  
A convergence criterion of reduction of residuals in the 
solved variables by four orders of magnitude is adopted. 
selection of a structured grid, instead of a more convenient 
unstructured one was due to more accurate results that may be 
obtained, at least for the case of the flow around a bluff body, 
using a structure grid as found in reference. Several attempts 
was taken to test different mesh distribution started with 583, 
200, with 14% increment, until it’s reaching 926,100 of total 
numbers of cell. These trials were made to all the cases and it 
shows a good results.  A 685,900 numbers of cells were
retained. Upwind spatial differential schemes have been used. 
Grid convergence tests have been performed to ascertain the 
adequacy of grid pattern use.
technique found in literature review were applied concerning 
the computational domain 
wind direction the computational domain was constructed had 
a height of 4H, width of 9H and length of 13H (H=5m)
 All fluid properties are assumed to be constant and
corresponding to those of air at 300 
sea level (101.3 kPa). In common notation, the following
values of molecular properties are u
1.846×10
−5
 N-s/m
2
; ν = 1.589
 
 
 Case 1 (a) 
 
Case 2 (a) 
 
Case 3 (a) 
 
Case 4 (a) 
ons which are the continuity 
. 
has occurred, or steady state has 
The 
 
 Consequently, a specific 
[7]. Thus, in the case of vertical 
 
 
K and standard pressure at 
 
sed: ρ = 1.1614 kg/m
3
; µ = 
×10
−5
 m
2
/s. 
 
Case 1 (b) 
 
Case 2 (b) 
 
Case 3 (b) 
 
Case 4 (b) 
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Case 5 (a) Case 
 
  
Fig. 1. Description of building models with single-sided ventilation
positive  x-direction; y is the upward-pointing vertical direction. 
 
The mathematical model applies numerical techniques to 
solve the Navier-Stokes continuity and energy equations for 
3D, turbulent fluid flow. In common notation, governing 
equations and turbulence-model constants are 
 

  0                                                                
 

 	 


  	



 	

  

 	

  i ju u 
        
- 	    	

 

                                                           
 
 

 	


 

  	

 !	"

 	  

 	




#

$
%
 
    &	'   ; (   ) 
)
 
 
*
 	

*
 

  	

+,"
*
 	 -
*
  

 	


 
where subscript t refers to turbulence; μ/  ρ
C2  0.09; C  1.44;	-  1.92;  89  1.0; 8* 
Fig. 2. Dimensions of computational domain
 
5 (b) 
. Mean wind is along the 
as follows [8] 
                (1) 
                               (2) 
        


 (                     (3) 


   -
*:
        (4) 
C2K ε= ; 	v/  μ/ ρ= ; 
1.0 
  
 
 
 
 Near the ground, the wind is strongly braked by obstacles 
and surface roughness. High
undisturbed air layers of the geostrophic wind (at approx. 5 km 
above ground) the wind is no longer influenced by the surface. 
Between these two extremes, wind speed changes with height. 
This phenomenon is called 
and with a neutrally stratisfied atmosphere, the logarithmic 
wind profile is a good estimation for the vertical wind 
 
? 
where h is the height from the ground

?@ABC the reference wind speed 
DEFG ,	DH the roughness height. In this work, the following 
values are employed: 
?@ABC
m [8]. The velocity component
equal to zero. 
 In order to determine the inlet turbulence values, 
turbulence intensity is assumed. For internal flows the 
turbulence intensity can be around 1
turbulence intensity is assumed
following relations are used for
computational flow domain
 
   I
JF
(  KL
M N= M
OP
 
where 
JF  is the average flow velocity, 
intensity, L is the reasonable length scale and 
Von Karman’s constant. 
According to the 
computational domain [7], a
the gradients of all the depen
vanish. Cross-ventilation (Case 5) was simulated in this 
investigation purposely to verify that the grid number of 
geometrical model used is trusted.
 above the ground in the 
vertical wind shear. In flat terrain 
shear [8]: 

?@ABC
QRS		 TTU			V
WXTABCTU 
 (5)  
, 
? wind speed at h, 
measured at reference height 
 = 5 m/s, href = 10 m and ho = 0.15 
s along Y and Z directions are 
-5%. For this simulation, 
 to be 5%. Therefore, the 
 K and ε at inlet to the 
: 
YZ [                                              (6) 
 
:=
                                                   (7) 
Y  is the turbulence 
κ = 0.41 is the 
literature, the outlet of the 
 constant pressure is assumed, while 
dent variables are assumed to 
 
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RESULT AND DISCUSSION 
 The main purpose of the present study is
flow patterns and air flow rate of sharp edges buildings and 
rounded edges buildings using RANS schem
wind driven natural ventilation in buildings
vertical lines in the middle section of the building A, B, and C 
are identified. Locations A and C have been chos
to describe the flow pattern close to the 
velocity components have been determined,
and vertical direction, respectively. The third velocity 
component in Z axis has been neglected as it
zero, due to the symmetry of the domain.  
The plots in Figs. 4 – 8 show the vertical distribution of X
direction velocity U for the 10 ventilation patterns evaluated. 
Numerical results have been obtained through 
shows in Table 1. 
 
Fig. 3. Location of air velocity is measured
 
 Fig. 9 illustrates the flow pattern inside 
five configuration considered in this analysis
4, and 5 it is found that the sharp edges and rounded edges has 
almost same flow pattern except for the Case 3. 
Among the configurations of single-sided ventilation, 
air flow rate of rounded edges is higher than sharp edges.
cross-ventilation (Case 5) shows a very high air flow rate 
compare to the single-sided but in this case the sharp edges has 
a higher flow rate than the rounded edges. It is believe the 
rounded edges not very much blocking the air flow through the 
top of building then it gives the good effect to the single
ventilation. 
 
Table 1: Numerical values of the ventilation rate (m
buildings 
 
Cases Air flow rate (m3/s) Cases 
Case 1 (a) 2.01 x 10-9 Case 1 (b) 
Case 2 (a) 4.01 x 10-8 Case 2 (b) 
Case 3 (a) 3.07 x 10-9 Case 3 (b) 
Case 4 (a) 6.69x 10-9 Case 4 (b) 
Case 5 (a) 7.2 x 100 Case 5 (b) 
 
 
 to investigate the 
e when modeling 
. In Fig. 3, three 
en in order 
openings. The 
 along streamwise 
 is supposed to be 
-
K-ε model. It is 
 
 of simulation 
the building for the 
. For the Case 1, 2 
  
the 
 The 
-sided 
3/s) of sharp edges 
Air flow rate (m3/s) 
2.29 x 10-5 
5.43 x 10-4 
7.66 x 10-4 
7.39 x 10-5 
7.01 x 100 
Fig. 4. Velocity distribution for 
Dots line: Sharp edges model; Solid line: Rounded edge model
0
2
4
6
8
10
-1 1
Y
 (
m
)
Section A : Case 1
0
2
4
6
8
10
-1 1
Y
 (
m
)
Section B :Case 1
0
2
4
6
8
10
-1 1
Y
 (
m
)
Section C: Case 1
 
 
 
single-sided, leeward ventilation (Case 1). 
 
3 5
U (m/s)
3 5
U (m/s)
3 5
U (m/s)
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Figure 6. Velocity distribution for single-sided, top ventilation (Case 3). Dots 
line: Sharp edges model; Solid line: Rounded edge model 
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section A : Case 3
0
2
4
6
8
10
-3 -1 1 3 5
Y
 (
m
)
U (m/s)
Section B : Case 3
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section C : Case 3
 
 
Fig. 5. Velocity distribution for single-sided, left-side ventilation (Case 2).  
Dots line: Sharp edges model; Solid line: Rounded edge model 
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section A : Case 2
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section B : Case 2
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section C : Case 2
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Figure.7. Velocity distribution for single-sided, windward ventilation (Case 
4). Dots line: Sharp edges model; Solid line: Rounded edge model 
 
 
 
Figure 8. Velocity distribution for single-sided, cross ventilation (Case 5). Dots 
line: Sharp edges model; Solid line: Rounded edge model 
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section A : Case 4
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section B : Case 4
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section C : Case 4
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section A : Case 5
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section B : Case 5
0
2
4
6
8
10
-1 1 3 5
Y
 (
m
)
U (m/s)
Section C 
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CONCULUSION 
 In the present study, Reynolds averaged Navier–Stokes 
approach has been applied to wind driven natural ventilation in 
a cubic building; ten different configurations were considered 
(Five configurations of sharp edges and another five 
configurations of rounded edges). The simulations were 
performed with the standard turbulence K–ε models. As a 
result, the velocity distribution inside and around the building 
was determined, and the ventilation rate.  
 The numerical results show that the rounded edges 
building will provide more ventilated air compared to sharp 
edges building. The cross ventilation been simulated for the 
verification of the right grid numbers used. Further 
computational investigation will be performed using RNG and 
LES. However, a further experimental investigation is needed 
to validate the simulation results. 
REFERENCES 
 
[1] Y. Wei, Z. Guo-qiang, W. Xiao et al., “Potential model 
for single-sided naturally ventilated buildings in 
China,” Solar Energy, vol. 84, no. 9, pp. 1595-1600. 
[2] R. M. Pulselli, E. Simoncini, and N. Marchettini, 
“Energy and emergy based cost-benefit evaluation of 
building envelopes relative to geographical location 
and climate,” Building and Environment, vol. 44, no. 
5, pp. 920-928, 2009. 
[3] P.F.Linden, “The Fluid Mechanics of Natural 
Ventilation,” Annual Rev. Fluid Mechanic, vol. 31, pp. 
201-238, 1999. 
[4] C. Atkins, "All in the Mind. Essential Matters 2007 ", 
2007. 
[5] J. Morrissey, T. Moore, and R. E. Horne, “Affordable 
passive solar design in a temperate climate: An 
experiment in residential building orientation,” 
Renewable Energy, vol. 36, no. 2, pp. 568-577. 
[6] J. Domingo, R. Barbero, A. Iranzo, “Analysis and 
optimization of ventilation systems for an underground 
transport interchange building under regular and 
emergency scenarios,” Tunnelling and Underground 
Space Technology, vol. 26, no. 1, pp. 179-188. 
[7] G. Evola, and V. Popov, “Computational analysis of 
wind driven natural ventilation in buildings,” Energy 
and Buildings, vol. 38, no. 5, pp. 491-501, 2006. 
[8] H.Versteeg, and W.Malalasekra, An Introduction to 
Computational Fluid Dynamics: The Finite Volume 
Method Approach, New York: John Wiley & Sons, 
1995. 
 
 
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COMPUTATIONAL STUDY OF SINGLE-SIDED VENTILATION THROUGH A 3- DIMENSIONAL ROOM WITH ROUNDED EDGES

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COMPUTATIONAL STUDY OF SINGLE-SIDED VENTILATION THROUGH A 3- DIMENSIONAL ROOM WITH ROUNDED EDGES

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