wind-induced pressure coefficients on buildings dedicated to air change rate assessment with cfd...
TRANSCRIPT
Wind-induced pressure coefficients
on buildings dedicated to air change
rate assessment with CFD tool in
complex urban areas
Stephane.SANQUER, [email protected]
1. INTRODUCTION
2. NUMERICAL APPROACH
3. VALIDATION
4. PRESSURE FIELD ON A BUILDINGS WALLS IN A COMPLEX URBAN AREA
5. CONCLUSION
0. CONTENTS
Air Flow inside the building depends on external condition.
Wind Mappings/Pressure on the wall are the key parameters to optimize the master plan.
Cp DataBase useful for simple building shape otherwise not accurate for
complex with neighboring buildings
Numerical method will help designers : Computation Fluid Dynamics
1. INTRODUCTION
2. NUMERICAL APPROACH
Equations :
RANS equation :
Turbulence Equation k-L :
0''
iji
i
j
j
i
jij
ijFuu
x
u
x
u
xx
P
x
uu
j
j
i
j
j
iTk
ik
Ti
i x
u
x
u
x
uP
x
kku
x
Tt Lk 2/1
TL
kC
2/3
𝐿𝑇 = 𝜅 𝐷𝑊𝐶𝐿
Turbulence viscosity :
Dissipation rate :Turbulence Length Scale
09.001.0 CDepends on thermal stability (Yamada and Arritt)
𝐶𝐿 ?
Two parameters to tune : 𝐶𝐿 𝑎𝑛𝑑 𝐶𝜇
3. VALIDATION
Turbulence model Reference XR/b XR_TOP/b
k-e (Standard) Tominaga el al. 2.7 No separation
k-e (Modified) Tominaga el al. 3 to 3.2 0.52 to 0.58
Differential stress model Mochida et al. 4.2 >1
LES Tominaga el al. 1 to 2.1 0.50 to 0.62
k-l (CL=0.20, Cmu=0.09) UrbaWind 1.7 0.25
k-l (CL=0.15, Cmu=0.09) UrbaWind 2.5 0.60
k-l (CL=0.10, Cmu=0.09) UrbaWind 2.5 0.70
k-l (CL=0.15, Cmu=0.01) UrbaWind 1.5 0.60
k-l (CL=0.10, Cmu=0.01) UrbaWind 2 0.70
Experiment Meng and Hibi 1.42 0.52
Flow Separation :
Dimension : 20 x 20 x 40 mb
3. VALIDATION
Pressure coefficient on buildings :
-1.5
-1.0
-0.5
0.0
0.5
1.0
0 1 2 3
CFD (UrbaWind)
0
3
2
1
Cp
Wind tunnel and full scale results range
Mean results
Experimental values from
the Silsoe 6m Cube (NZ)
4. PRESSURE FIELD ON A BUILDINGS WALLS IN A COMPLEX
URBAN AREA
Sensibility of geometry of the building and wind direction
Cp=0 Cp=0.5
Cp=0.6 Cp=0.6
Impact of geometry
Imp
act
of w
ind
direct
ion
4. PRESSURE FIELD ON A BUILDINGS WALLS IN A COMPLEX
URBAN AREA
-1.5
-1.0
-0.5
0.0
0.5
1.0
0 1 2 3
0°-Detached
45°-Detached
0°- Urban
45° - Urban
0
3
2
1
Cp
0° 45°
CFD (DCp) 0° 45°
Detached 1.0 0.7
Urban 0.1 0.2
Table (DCp) 0° 45°
Urban 0.45 0.35
Influence of complex urban environment
DCp over estimated using table.
WINDa UCpAQ
4. PRESSURE FIELD ON A BUILDINGS WALLS IN A COMPLEX
URBAN AREA
H H H
H
H
M
L
L
L L
H
H
H HM
Influence of complex urban environment
H = High (DCp≥0.39) / M = Medium (0.17≤ DCp<0.39) / L = Low (DCp<0.17) Level of Natural Ventilation
Formulae or tables difficult to apply in a complex urban environment
5. CONCLUSION
Pressure Coefficient are sensible to wind direction, building shape, building environment.
Be careful when apply formulae or use table.
CFD tools can deal with complex area.
Thanks you