AixLib.Airflow.WindowVentilation.Utilities.WindProfilePowerLaw

# .AixLib.Airflow.WindowVentilation.Utilities.WindProfilePowerLaw

Wind profile power law relationship of Hellmann

## Information

This model contains the wind profile power law relationship of Hellmann.

The power law allows for the calculation of wind speeds at different heightghts based on the reference speed and heightght.

#### Roughness Classes and Lengths

#### Roughness class | #### Roughness length / m | #### Land cover types
0 | 0.0002 | Water surfaces: seas and Lakes
0.5 | 0.0024 | Open terrain with smooth surface, e.g. concrete, airport runways, mown grass etc.
1 | 0.03 | Open agricultural land without fences and hedges; maybe some far apart buildings and very gentle hills
1.5 | 0.055 | Agricultural land with a few buildings and 8 m high hedges seperated by more than 1 km
2 | 0.1 | Agricultural land with a few buildings and 8 m high hedges seperated by approx. 500 m
2.5 | 0.2 | Agricultural land with many trees, bushes and plants, or 8 m high hedges seperated by approx. 250 m
3 | 0.4 | Towns, villages, agricultural land with many or high hedges, forests and very rough and uneven terrain
3.5 | 0.6 | Large towns with high buildings
4 | 1.6 | Large cities with high buildings and skyscrapers

#### References

Hau, E. (2016). Windkraftanlagen: Grundlagen, Technik, Einsatz, Wirtschaftlichkeit (6. Auflage). Springer Vieweg.

https://wind-data.ch/tools/profile.php

## Revisions

- June 13, 2024, by Jun Jiang:
  First implementation (see issue 1492)

Generated at 2026-05-09T18:18:56Z by OpenModelicaOpenModelica 1.26.7 using GenerateDoc.mos