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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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CFD-Reference: W.D. Baines tall building 6/6

Figure 4: CFD solution (model configuration v.1)