baines reference
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CFD-Reference: Tall building in a boundary-layer
velocity field
As reference example for the application of the CFD module of PHYSICA in the field of
building aerodynamics the pressure distributions over the sidees and the top of a tall
building model have been computed. The obtained results are then compared to the
experimental results of:
[1] W.D. Baines:Effects of Velocity Distribution on Wind Loads and Flow Patterns on
Buildings. Proceedings of Symposium No. 16: Wind Effects on Buildings and Structures,
held at the National Physical Laboratory, England, 1963. Published by HMSO London1965.
which can be found together with other experimental results in the field of bluff-body
aerodynamics in:
[2] E. Simiu, R. Scanlan:Wind Effects On Structures. Third Edition, John Wiley and
Sons. 1996. Pp. 164-165
Geometrical Parameters
The fluid domain was discretized using an automatic tetrahedra netgenerator. Further modelconfigurations are listed in a table given below.
Model configuration v.1 v.2 v.3
Height of building 160.0m
Side length 19.72m
Height/ Side ratio 8.1143
Total length of
domain (in-flow dir.)
1000.0m
Total width (cross-
flow dir.)
600.0m
Total height () 600.0m
Upstream length (luff
side of building)
200.0m
Blocking ratio 0.88%
Finite volumes 90373
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Figure 1: Fluid domain (90373 tetrahedral volumes), detail building (below)
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Inflow condition, turbulence parameters
The inflow condition was set to a boundary layer wind profile using SOFiLOAD:
WINDLOADING
Wind according to code DIN 1055-4 (2004) Zone 2 Terrain category Regelprofil Binnenland
atmospheric wind v = 64.02 [m/sec]
Mean reference wind speed vref = 25.00 [m/sec]
Wind direction 1.000 0.000 0.000
Reference point 0.000 0.000 0.000 [m]
Reference direction 0.000 1.000 0.000
Surface height 0.000 [m]
- Coefficients o(Karman) A1 A2 A3 B1 B2 C coherences
Longitudinal 4.000 0.000 0.000 0.000 70.800 0.833 0.221 0.110 0.110
Lateral 4.000 0.000 3021.00 0.000 283.200 1.833 0.114 0.167 0.167
Vertical 4.000 0.000 3021.00 0.000 283.200 1.833 0.114 0.167 0.167
Windprofiles (according to design code or explicit specification)
h v-mean v-boe t-lon t-lat t-ver l-lon l-lat l-ver phase
[m] [m/sec] [m/sec] [m/sec] [m/sec] [m/sec] [m] [m] [m] [-]
8.000 20.33 31.43 4.73 0.00 0.00 79.986 0.000 0.000 0.000
82.000 35.01 46.66 4.75 0.00 0.00 206.216 0.000 0.000 0.000157.000 38.84 50.44 4.75 0.00 0.00 251.743 0.000 0.000 0.000
231.000 41.32 52.84 4.75 0.00 0.00 280.249 0.000 0.000 0.000
305.000 43.19 54.63 4.75 0.00 0.00 301.259 0.000 0.000 0.000
379.000 44.72 56.07 4.75 0.00 0.00 317.904 0.000 0.000 0.000
454.000 46.03 57.30 4.75 0.00 0.00 331.851 0.000 0.000 0.000
528.000 47.16 58.35 4.75 0.00 0.00 343.573 0.000 0.000 0.000
602.000 48.16 59.27 4.75 0.00 0.00 353.784 0.000 0.000 0.000
The pressure distribution of the reference solution is given as pressure coefficients, i.e.
pressure divided by the stagnation pressure:
So here we use the following constants:
vref = 38.96 m/s (Reference velocity on highest point of building)
= 1.25 kg/m (Reference density of air)
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cp=p
1
2v ref
2
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The turbulence parameters for the k- standard model where identified with a turbulence
intensity T = 10 % and a length scale of Lt = 20m (side length of building) according:
to:
k = 7.70 m/s (variance of velocity)
= 1.25 m/s (eddy energy dissipation)
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k=1
2T v ref
2
=k
3
2
Lt
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Figure 3: Reference solution [2]
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Figure 4: CFD solution (model configuration v.1)