








































 American Journal of Agricultural Science, Engineering and Technology 

COMPUTATIONAL STUDY OF CANARY GREENHOUSE SIDE WALL AND ROOF 

VENTS OPENING EFFECT ON NOCTURNAL AIRFLOW AND CLIMATE 

PATTERNS 

Hassan Majdoubi
1,3*, Hicham Fatnassi

2
, Thierry Boulard

2
, Allal Senhaji

3
, Salma Elbahi

1
, Hassan 

Demrati
4
, M’hamed Mouqallid

3
, Lahcen Bouirden

4 

ABSTRACT 

The following paper presents a Computational Fluid Dynamic (CFD) comparative study of 

the effect of side wall and roofs vents openings on canary greenhouse airflow circulation and 

climate distribution under different ventilation processes. The investigation was conducted in 

a one hectare canary greenhouse type, which is the most widespread type in the whole 

Mediterranean and along the Atlantic coast area of Morocco, especially in souss vally region. 

The simulations were performed with the commercial code CFD2000 based on the solution of 

the partial differential equations, which describe the flows, and was obtained by discretizing 

the space and time and solving the transport equations on the spatial grid as difference 

equations, used a finite volume discretization. The standard two equations k-ε model was 

used to describe the turbulent transport. The influence of external factors such the cover 

temperature, the wind speed, on the flow was simulated by boundary conditions, these values 

were obtained from experimental results. Simulations were conducted with a fixed wind 

speed equal 1.05 m/sec, tomato crop rows oriented north-south and the ventilation openings 

are continuous and equipped with insects screen type 20/10. Results reveal that ventilation 

opening arrangements strongly affects the greenhouse wind speed, which can generate a 

heterogeneous climate, especially during daytime. But in the other hand, results confirm that 

there is no significant effect of the side wall vents opening on canary greenhouse air 

temperature and humidity fields. 

Key words: Greenhouse, CFD, Insect screen, Ventilation openings, Climate 

___________________________________________________________________________ 
1
Laboratoire de Recherche Scientifique et Pédagogique au Monde Méditerranéen, CRMEF 

Meknès-Tafilalet, Meknès, Maroc,  majdoubi76@yahoo.fr 
2
INRA, Univ. Nice Sophia Antipolis, CNRS, UMR 1355-7254 Institut Sophia Agrobiotech, 

06900 Sophia Antipolis, France 
3
Equipe de recherche en Energétique et Mécanique des Fluides, ENSAM Meknès, Maroc 

4
Laboratoire de Thermodynamique et Energétique (LTE), Faculté des Sciences, Agadir, Maroc 

*Corresponding Author

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INTRODUCTION 

Greenhouse production technology systems, no matter where, consist of fundamental climate control 

components, and depending on their design and complexity, they can provide a greater or lesser amount 

of climate control, and subsequent plant growth and productivity. Temperature and humidity are the most 

important parameters of the greenhouse climate that needs to be controlled in order to achieve optimal 

plant growth and maximize the yield. During day time especially in hot climate conditions, the major 

concern for greenhouse climate management is to extract the excess energy. This can be obtained by 

removing the extra heat through air exchange by means of ventilation openings. Contrarily, by night, 

especially in cold climate conditions, the challenge for greenhouse growers is to keep the heat received 

during the day in order to have a higher inside temperature than outside. This can be realized by using an 

internal curtain and/ or closed the ventilations openings. 

Natural ventilation is most important for controlling the temperature and humidity level. Several studies 

were been conducted on ventilation rate effect on airflow and microclimate distribution. Feuilloley et al., 

1994, suggested a simple and efficient way for a grower or constructor to determine the dimension of the 

vents of natural ventilation for tunnel greenhouses in Mediterranean climate. Boulard et al., (1995 a & b), 

have studied by measurements the air exchange rate of a twin-span plastic greenhouse with continuous 

roof vents and by simulation. Kittas et al., (1995 & 1996), studied again the ventilation in the same 

greenhouse as Boulard et al., (1995) presented a non-dimensional ventilation function per unit of 

greenhouse window and ground areas, respectively. Sase et al., (2006), have analyzed the air movement 

and their effect on microclimate uniformity in a single span ventilated greenhouse. They show that the 

internal air movement in a naturally-ventilated greenhouse is affected by many factors such as wind 

velocity, wind direction, temperature difference between internal and external air, greenhouse structure 

and vent configuration that includes size, shape and arrangement of vent openings. Also Willits (2006) 

examined the effect of airflow rate, outside relative humidity, and canopy size on the behavior of the 

evapotranspiration coefficient and upon thermal stratification. 

Fatnassi et al., (2009), experimental study confirmed the dependence of the greenhouse tunnel ventilation 

on wind direction and crop status, results show that the air exchange rate of a tunnel type greenhouse 

decreases with crop height, the high leaf density near the ventilation opening area causing an additional 

air pressure drop. More Recently, the coupled approach between energy balance simulations and 

computational fluid dynamics was used by Piscia et al., (2015), in order to analyze the effects of 

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 American Journal of Agricultural Science, Engineering and Technology 

ventilation on greenhouse climate under different sky climate conditions, the study‟s results indicate that 

ventilation during the night-time, in winter time,  improves greenhouse climate; in the clear-sky case, 

relative humidity was reduced and the temperature was raised since ventilation reduced or eliminated 

thermal inversion, whereas in the covered-sky situation, ventilating reduced the humidity content, but the 

temperature dropped. 

Canary and Spanish „Parral‟ greenhouse are naturally ventilated through the combination of sidewalls, 

operated manually, and opened fixed roof ventilators openings. Unfortunately, up to now, very few 

studies were conducted on canary greenhouse ventilation openings effect on airflow and microclimate 

distribution. Demrati et al., (2007), have used the energy balance method to predict the greenhouse 

ventilation rate of a banana crop canary greenhouse. Some authors used computer programs to investigate 

the influence of insect screens and predict the inside microclimate distribution, Fatnassi et al., (2003 & 

2006) have characterized the inside climate distribution and the air exchange rate of 0.5 ha canary type 

greenhouse, equipped with insect screens (6×6) on side and roof ventilation openings, then used these 

data for the validation of a three dimensional CFD simulation model. Campen (2003) and Molina-Aiz 

(2004) have analyzed the effect of wind speed and direction and the ventilation openings design on 

natural ventilation of a Spanish „Parral‟ greenhouse equipped with screened top and side ventilation. 

Result obtained by Majdoubi et al., (2007), showed that the relatively “bad” ventilation performance of 

canary greenhouse is not a result of the low value of the greenhouse wind−related ventilation efficiency 

coefficient (Cw) but a result of the low value of the discharge coefficient (Cd), caused by a high pressure 

drop along the air circulation. This latter is generated both by the use of fine insect screens with small 

openings and obstruction due to the crop rows orientation which was perpendicular to the prevailing wind 

direction.  

As a previous CFD study, Majdoubi et al., (2009), have analyzed the air circulation and the distributed 

climate during daytime in a 1-ha Canary type tomato greenhouse in the coastal area of southern Morocco. 

Analyses show that even with low outside wind speed, the outside wind governs the inside airflow, 

inducing a strong wind wise air current above the canopy and a very slow reverse flow inside the crop 

canopy. The weak air exchange within the canopy governs the climate at this level, with a major increase 

in air temperature and a more moderate increase in specific humidity. Keeping in mind these researches, 

in this paper, was designed a 3D CFD model to investigate the effect of different ventilation openings 

configurations on canary greenhouse climate during night time. Simulation conducted in the same 

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 American Journal of Agricultural Science, Engineering and Technology 

greenhouse already studied by Majdoubi et al., (2009) by using a commercial CFD package (CFD2000
®
/ 

Storm), the airflow circulation, temperature and humidity fields within a real large scale Moroccan canary 

greenhouse (1.125 ha area) equipped with insect screens (20/10) on the roof and sidewalls ventilation 

openings. A realistic model based on energy, mass and momentum exchanges was considered. As the 

regime in greenhouse is turbulent, the turbulent transfers were described by a k-ε model. Likewise, the 

dynamic influences of insect screens and tomato crop on airflow movement were modeled by means of 

the concept of porous medium with the Boussinesq assumption. Atmospheric radiations contribution was 

included in the model by customizing the roof cover temperature deducted from its energy balance by 

means of view factor law. Also, the CFD code was customized in order to simulate, in each element of the 

crop cover, the sensible and latent heat exchanges between tomato crop and greenhouse. 

The CFD Model 

i. Fluid flow equation

The velocity field U, and the associated temperature field T or water vapor content w can be 

deduced at any time from the resolution of the mass, momentum and energy balances: 

   (1) 

Where  is the studied variable, either the three components of the speed vector, the 

temperature T or a given mass component such as the air humidity content w,  is the diffusion 

coefficient of the quantity  , S the source term and jU the speed component. The governing 

equations are discretized following the procedure descripted by Patankar (1980). This consists of 

integrating the governing equations over a control volume. Theses equations are numerically 

solved using a finite volume code CFD2000 using the PISO algorithm developed by Issa (1985) 

(CFD2000
®
 manual, 2004). This code also allows for the modeling of the turbulent constraints

by means of the standard k- turbulence model (Launder, 1974). 

ii. Flow through a porous medium

In order to include the drag effect inducted by the insect screens and the crop cover, into our 

CFD study, the insect screens and the crop cover were simulated as porous medium and the air 

flows governed by the Darcy-Forchheimer equation (2): 















 S
XX

U
X j jj

j

j j

)()(
11 















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    )( 2UKCUKS F  (2) 

Where U is the air speed,  is the dynamic viscosity of the fluid, K is the permeability of the 

porous medium and is the non-linear momentum loss coefficient. The values of the aerodynamic 

proprieties (K and CF) of the porous medium (screen) were calculated using relations from 

literature, which correlate these proprieties with the porosity (Miguel, 1997) 

1,69103,44 K       (3) 

2,132 /104,30 FC        (4) 

Where   is screen porosity, it can be deduced from the dimensions of the thread [21]: 

 ))((. dldLlL  (5) 

Where L = 0.788 mm and  = 0.255 mm are mesh‟s length and width respectively, and d = 0.28 

mm, is the wire diameter.  

For the crop, this sink of momentum is proportional to the leaf density and it may be expressed 

by unit volume of the cover by the commonly used formula (Bruse, 1998):  

2UCLAIS D (6) 

Where LAI is the leaf area index and CD is the drag coefficient of the vegetal cover. For a 

mature greenhouse tomato crop, Haxaire (1999) found 0.32DC  , using wind tunnel facilities.  

For the crop and the range of air speed observed into the cover, the term in U of equation (2) can 

be neglected in front of the quadratic term and the non-linear momentum loss coefficient CF and 

the permeability K of the medium can be deduced from the combination of equations (2) and (6): 

DF CLAIKC  (7) 

For our simulations, the tomato crop cover was assimilated to a unique 2.6 m high parallelepiped 

block of porous medium with the same length and width than the greenhouse and with a leaf area 

index, LAI, equal to 3, the drag coefficient CD being equal to 0.32 (Haxaire, 1999) 

iii. Simulation of dynamic, thermal and hydrous effects of the crop cover

The coupled sensible and latent heat balances were considered at crop level by means of the 

equations describing respectively the sensible and the latent exchange, within each mesh of the 

crop assimilated to a porous medium, between the greenhouse air and the solid matrix of the 

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porous medium. The radiative flux, reaching each mesh of the crop cover was assimilated to a 

"volumic heat source boundary condition" and partitioned into convective sensible and latent 

heat flux (water vapor) depending on the heat and water exchanges between air and the virtual 

solid matrix representing the crop cover and characterized by its surface temperature: 

0 latsensnet QQR (8) 

The sensible heat flux SenQ  can be expressed with respect to the difference of temperature 

between inside air and the canopy:

  aivpSen rTTLAICQ   (9) 

and the latent heat flux LatQ   deduced from a similar relation : 

    saivevLat rrwwLAILLQ  *3

1

   (10) 

Where pC  and  are respectively the specific heat of air at constant pressure (J kg
-1

 K
-1

) and the

air density (kg m
-3

), iT is the greenhouse air temperature (K), vT is the vegetation temperature 

(K), ar the aerodynamic resistance between the leaf and the air within each mesh (s m
-1

), vL is 

the latent heat of vaporisation of water (J kg
-1

), *

vw is the saturated water content of the air at

vegetation temperature (kg kg
-1

), iw is the air water vapor content (kg kg
-1

), sr is the leaf stomatal

resistance (s m
-1

) and eL the Lewis number.

In order to take into account these new exchanges, the CFD code was customized by means of a 

"source model" (Haxaire, 1999): 

)var.( iableDependentvalueCoefSource  (11) 

Where the different terms of this equation were identified with the terms of the sensible and

latent heat transfer equations between the crop cover and the air within each mesh, i.e. for the 

temperature : 

arCpLAICoef  and vTvalue  , 

and for air humidity: 

saev rrLLLAICoef  3
1

...  and vwvalue  . 

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The aerodynamic resistance 
ar was deduced from the air speed within each mesh:

  5.0

0.288 UdCr vpa


           (12) 

Where vd is the characteristic length of the leaf (m), iU the interior air speed (m s-1),   is the air 

thermal conductivity (W m
-1

 K
-1

) and  is the air viscosity.

The radiative flux was considered as not limiting and the tomato leaf stomatal resistance deduced 

from air temperature and saturation deficit (Boulard et al., 1991): 































)1629106.107(0.34exp0.111 max

237.5

7.5

min
Dwrr i

T

T

ss
i

i

    (13) 

Where: 1150
min

 msrs   et  mbarD 10max 

Tomato crop temperature and humidity can be customized and calculated in simulation model 

according to the following equations (Majdoubi et al., 2009): 

   







 
 ).

)(
(

2

1

.

int
int v

t

a
v

vp

a
f Lai

r

ww
L

dz

zdR

LAIC

r
TT 


    (14) 




















saa

a

s

faf

a

f

s rrr

w

r

w
worww

r
ww

r

11
/)()( int

int


       (15) 

with LAI is the crop stand leaf area index and R(z) is the global radiation inside the greenhouse 

v. Meshes and boundary conditions

The computational grid used Cartesian body fitted coordinates and after several trials with 

different densities, the calculations were based on a 192 by 44 by 112 grid with finer resolutions 

were imposed near soil, walls and roof, due to stronger thermal gradients (Figure 1) (Majdoubi et 

al., 2009). The boundary conditions prescribed a null pressure gradient in the air, at the limit of 

the computational domain. The outside air speed was perpendicular to the West–East sidewalls 

ventilation openings with a measured value equal 1.05 ms
-1

. The driving force of natural

convection is the wind force and buoyancy force arising from small temperature differences 

within the flow according to the boussinesq hypothesis. The averages and standard deviations of 

the climate boundary conditions are summarized in Table 1. 

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Figure 1.Computational grid of the whole domain for the CFD simulation (Greenhouse, tomato crop and 

insect screens) 

Table 1. Experimental measurement (mean and S.D) performed between 2 and 5 h (end of night) 

during 3 days during summer time and used as boundary conditions for the simulation 

 Parameters Mean S.D

Outside temperature eT  (°C) 18.67 1.05 

Outside relative humidity eHR

(%) 
91.49 3.6 

Sky temperature Tsky(°C) 6.23 0.75 

Crop cover temperature vT  (°C) 18.11 1.23 

Soil surface temperature siT (°C) 20.34 0.98 

Wind direction  D v (degré) 120.11 10.45 

Wind speed  U (m/s) 1.05 0.023 

Solar radiation (W/m
2
) 0 0 

Net radiation Rnet (W/m
2
) -9.15 0.53 

Inside soil surface flux  Fs (W/m
2
) -15 1.21 

MATERIALS AND METHODS 

i. Site and greenhouse description

The experimental greenhouse is a large scale commercial canary plastic greenhouse covered with 

a 200 µm thickness single layer polyethylene plastic. Its surface occupies 1.125 ha (90 m length 

and 125 m width) with a height of 5 m at the gutter and 5.5 m at the ridge and was surrounded by 

similar greenhouses. The orientation of its spans and tomato crop rows was North-South, i.e, 

perpendicular to the direction of the prevailing sea wind.  

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Greenhouse ventilation was performed by means of seventeen roof ventilation openings 

(0.6×125 m
2
 each, total of 1.275 m

2
) covered with insect screens (20 meshes.cm

-1
 in width, 10

meshes.cm
-1

 in length with a wire diameter of 0.28 mm). The sidewalls ventilation openings

were equipped with similar insect screens.  The maximal opening areas reached 875 m² for the 

West-East sides and 630 m
2
 for the North-South sides. During the experiment, the roof and

sidewalls openings were maintained unchanged and equal to 1,275 m
2
 and 1,505 m

2
 respectively

(Figure 2). 

The greenhouse was occupied by a tomato crop (Solanum Lycopersicum, cv. Gabriella) planted 

with a plant density of 1.8 plant m
-2

 and north-south oriented rows, i.e. perpendicular to the

prevailing see breeze direction coming from west. 

Figure 2. Schematic view of the studied greenhouse, its ventilation system and the surrounding. 

ii. Inside and outside climatic parameters measurements

The following parameters were systematically recorded: 

 The inside net radiation Rnet was monitored by means a net radiometer (Q-7, Campbell

Scientific Ltd, UK), situated between the top of the crop canopy and the polyethylene

film of the roof.

 The inside conductive heat flux exchange at soil surface FS which was measured by

means of a conductive flux meter (HFT3, Campbell Scientific Ltd, UK) situated 1 mm

below the soil surface.

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 The inside and outside air temperature T and relative humidity HR were measured by

means of thermo-hygrometers probes (HMP45 AC, Vaisala, Etoile Internationale, Paris)

 The inside soil surface, roof cover, tomato leaf temperatures were measured by means of

thermocouples (Copper- Constantan) which were stuck on the plastic or positioned 1mm

below the soil surface together with fine thermocouples which were inserted in the

principal vein of the terminal leaflet on the lower face of a leaf.

 The outside wind speed U and direction Dv were measured by means of a cup

anemometer and a wind vane (W200P, Campbell Scientific Ltd, UK) located 8.5 m high

on a mast situated 3 m over the greenhouse ridge (A 100R. Campbell Scientific Ltd, UK).

 The outside global radiation Rgo was measured by means a pyranometer (SP-LITE, Kipp

& Zonen, Campbell Scientific Ltd, UK).

The parameters described in Table 1 were systematically recorded, in order to determine the 

simulation boundary conditions and to validate the simulation model. 

RESULTS AND DISCUSSIONS 

After validation of our model (Majdoubi, 2007) details of air wind speed, temperature and 

specific humidity patterns in vertical or longitudinal profiles of the three studies cases: i) the 4 

sidewall closed (TPF), ii) the north and south sidewall closed (PNSF) and iii) the 4 sidewall 

opened (TPO), were presented in figures 3 to 13. 

i. Airflow circulation

For an outside wind direction perpendicular to the roof ventilation openings (i.e. west-east). 

Figure 3, illustrates a vertical cross-section along the flow direction in the middle of the 

greenhouse for the three configurations. It shows the development, at the level of crop cover, of a 

reverse flow from the leeward end to windward end part of the greenhouse for the three studies 

configurations, the wind speed at this level being much lower than above vegetation. However, it 

is noted that, with a north-south side wall ventilation opening closed, the velocity above the 

canopy is greater than for the other configurations. Velocity profiles are similar in the case where 

the sidewall ventilation openings are fully closed or open, either in or above the vegetation. 

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It therefore appears that, paradoxically, the closure of the North-South sidewall ventilation 

openings contributes significantly to increase the air exchange in the greenhouse, the roof 

ventilation opening also contributing significantly. The air velocity profiles across the middle of 

the greenhouse at heights of 1, 3 and 4 m were reported in Figures 4, 5 and 6. Results confirm 

the results of the previous figure concerning the airflow. The velocities in the vegetation at 1m 

above the soil surface are low in all three cases, with however a slight increase of wind speed in 

the case where the north and south sidewalls ventilation opening are closed. At the level of 3 m 

and 4 m above soil area, we also note that with a north and south sidewalls ventilation openings 

closed, the wind speed is highest in the greenhouse. Consequently, we can conclude that the 

contribution of the west sidewall ventilation opening, limited of an effect in the first 30 meters 

from the windward of the ventilation opening. After these are the roof ventilation openings 

which feed the air circulation in the greenhouse. 

These results confirm that greenhouse air velocity is governed mainly by roof ventilation 

openings at the gutter and it appears clearly that the roof openings are alternatively acted as air 

entrances and exits, which confirm the results observed by Majdoubi et al., 2009. 

Figure 3. Modeled profile of mean horizontal 

wind speed in the center of the greenhouse with 

three different vent configurations. 

Figure 4. Modeled horizontal air velocity profiles 

across the middle of the greenhouse along West–East 

direction at height 1m above soil surface. 

0

1

2

3

4

5

6

7

8

9

10

-0,2 0 0,2 0,4 0,6 0,8 1 1,2

H
e
ig

h
t,

 (
m

)

Velocity, (m,s-1)

TPF PNSF TPO

-0,2

0

0,2

0,4

0,6

0,8

1

1,2

20 40 60 80 100 120 140

V
e

lo
c

it
y,

  
(m

,s
-1

)

Length( west- east) ( m)

TPF PNSF TPO

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Figure 5. Modeled horizontal air velocity profiles 

across the middle of the greenhouse along West–

East direction at height 3m above soil surface. 

Figure 6. Modeled horizontal air velocity profiles 

across the middle of the greenhouse along West–East 

direction at height 4m above soil surface. 

Figures 7 and 8 illustrate the horizontal velocity profiles respectively at 1 and 4 m above the 

ground (from north to south). Results show that the north opening and south one contribute 

mainly to increase in the air wind speed only near the sides (up to 4 m), for the profile practiced 

at 1 m above the ground. 

Figure 7. Modeled horizontal air velocity profiles 

across the middle of the greenhouse along North-

South direction at height 1m above soil surface. 

Figure 8. Modeled horizontal air velocity profiles 

across the middle of the greenhouse along North-

South direction at height 4m above soil surface. 

ii. Temperature and humidity patterns

Figures 9 and 10 illustrate respectively the vertical profiles of simulated air temperature and 

specific humidity in the center of the greenhouse respect to the height. We can observe through 

the previous figures that there is no significant difference of air temperature and specific 

-0,2

0

0,2

0,4

0,6

0,8

1

1,2

20 40 60 80 100 120 140

V
e
lo

c
it

y
, 

(m
,s

-1
)

Length (weast-east), (m)

TPF PNSF TPO

-0,2

0

0,2

0,4

0,6

0,8

1

1,2

20 40 60 80 100 120 140

V
e
lo

c
it

y
, 

(m
,s

-1
)

Length (west- east), (m)

PTF PNSF PTO

-0,2

0

0,2

0,4

0,6

0,8

1

1,2

20 40 60 80 100 120 140 160

V
e
lo

c
it

y
, 

(m
,s

-1
)

Width (north-south), (m)

TPF PNSF TPO

-0,2

0

0,2

0,4

0,6

0,8

1

1,2

20 40 60 80 100 120 140 160

V
e
lo

c
it

y
, 

(m
,s

-1
)

Width (north-south), (m)

TPF PNSF TPO

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humidity between the three cases except at the soil surface where it is found that the temperature 

and specific humidity were higher (by about respectively 0.5° C and 5.66 10
-5

) in the case where

the four sidewalls ventilation openings ware open. 

Figure 9. Modeled vertical profile of air temperature 

in the centre of the greenhouse between two 

successive roof openings. 

Figure 10. Modeled vertical profile of air 

specific humidity in the centre of the greenhouse 

between two successive roof openings. 

Figures 11 and 12 show the air temperature and specific humidity profiles respectively along the 

length of the greenhouse at 1m above the ground. It is clear that the closing or opening of the 

sidewalls has no significant effect on canary greenhouse air temperature during the nighttime, 

but we can observe a slight increase of specific humidity for the case with all side wall 

ventilation openings were open. 

Figure 11. Modeled horizontal profiles of air 

temperature in the centre of the greenhouse from 

the West to the East at 1m high above soil 

surface. 

Figure 12. Modeled horizontal profiles of air specific 

humidity in the centre of the greenhouse from the 

West to the East at 1m high above soil surface.  

The horizontal profiles of air temperature and specific humidity respectively at 1m above the 

ground as a function of the width of the greenhouse (from north to south) were plotted in figure 

0

2

4

6

8

10

12

290 291 292 293 294

H
e

ig
h

t,
 (

m
)

Temperature, (K)

TPF PNSF TPO

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12 and 13, we can observe that temperature and specific humidity values are the same for all 

configurations and that the climate is homogeneous at the same height. 

Figure 13. Modeled horizontal air temperature 

profiles across the middle of the greenhouse 

along North-South direction at height 1m above 

soil surface. 

Figure 14. Modelled horizontal air specific humidity 

profiles across the middle of the greenhouse along 

North-South direction at height 1m above soil 

surface. 

CONCLUSION 

A 3D numerical simulation model of large scale canary greenhouse was developed and validated. 

Based on our results for the three vents opening configurations studied (the 4 side wall vents 

opening closed, the north-south side wall vents opening closed and the 4 side wall vents opening 

opened), it appears that during night time there is no significant effect of side wall vents opening 

on canary greenhouse wind speed, temperature and humidity values compared with the outside 

climate. So, we can make the following points: 

The opening of the forth greenhouse sidewall is not the configuration which can allows a 

maximum air exchange and therefore the moisture management related to the transpiration of the 

crop. 

The closure of the forth is accompanied by a limitation of the greenhouse air velocity, and thus 

renewed, but curiously does not induce increase moisture in the vegetation. This is paradoxical 

but is not very well explained. 

The opening only of the side wall located upwind and downwind accelerates the greenhouse air 

circulation which thus enables to remove excess moisture generated by perspiration of culture. 

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