Computational Fluid Dynamics, horizontal flow through buildings

Computational Fluid Dynamics, horizontal flow through buildings

Outdoor air supply with facade ventilation devices
Outdoor air supply with facade ventilation devices "MŁnchner Tor"

Today, buildings are often designed to reduce mechanical ventilation for most of the operating time. Consequently, in planning these buildings, there is the need for a secure forecast of the natural ventilation efficiency. Computational Fluid Dynamics is used here.

In the case of natural ventilation of buildings, leakages in the external envelope of the building result from openable windows and seams at shut windows, leading to air infiltration into the building due to pressure differences between the outer environment and the inside of the building. These differences in pressure arise because of the interaction of wind forces and temperature differences between the inside and the outside of the building.

Due to the incoming wind flow at a skyscraper building, considerable differences in pressure with considerable luv and lee zones can occur on the shell surface. When the windows are open, the wind pressures also penetrate into the inside of the building and can result in unwanted effects within the storey there.


Effects that can be found often are:

  • Increased opening forces at closed doors and windows
  • Draughts in offices, corridors and entrance areas
  • Air flow noises at seams/joints and doors
  • Doors slamming shut
They determine the limits of natural ventilation.

Computational Fluid Dynamics tends to reduce those limitations in window ventilation as far as possible due to wind stress by targeted measures, e.g. in facade construction or window design. Today, especially in case of high-rise buildings, decentral facade ventilation devices are often on the short list to save expenses in systems.

The efficiency of these ventilation devices (power requirement, flow rate) also depends on the pressures at the exterior facade and the flow resistances of both facades and interior.

For recording the outer conditions in real terms Computational Fluid Dynamics is normally preceded by wind tunnel tests.



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