Calculations are made for the wind directions that are considered to be the most favourable when outdoors. Consideration is given to buildings and essential topography within the neighbourhood.
The local wind environment is, to a great extent, governed by how the buildings are designed. To provide more direct answers regarding the wind environment that can be expected for a particular proposed construction, it is often the final proposals for the design which need to be studied in detail. This can be done with computer simulations of the wind environment.
The results from flow calculations are presented in the form of a so-called relative wind -this is because wind comfort criteria are based on this parameter. When calculating the relative wind, the effects of gusts (turbulence) is included. Turbulence makes the wind feel much stronger than if the wind speed had been the same but without the turbulence.
Besides the results from the flow calculations, wind statistics are also provided from the nearest weather station. Wind statistics provide a measure of how representative the wind directions examined are for the wind environment in general and, in this way, makes the interpretation of the results easier.
For this study, emphasis should be made on the differences in wind speed within the area, even if the results may be regarded as a good approximation of the absolute values.
Alternative solutions for garden areas and land development
Flow calculations provide answers regarding how planned measures to improve the wind environment can be expected to work. The calculations are made with and without the planned measures (bushes, trees, wind screens etc.), and are then compared to find the optimal solution.
Comparative studies can also be carried out as a part of the EID in order to determine whether the wind environment within an area changes when new buildings/constructions are erected and to what degree things change.
The spread of particles and air pollutants
Construction work carried out in heavily trafficked areas or close to other important emission sources must take into consideration the spread of air pollutants. Information regarding the levels of air pollutants which can be expected in different areas around a construction site is helpful when positioning ventilation outlets and when planning outdoor environments around buildings.
SMHI also calculates the levels of air pollutants from a regional scale to the area around a particular building. With CFD (Computational Fluid Dynamics) technology, a very high resolution image of the expected levels can be obtained. Besides emissions from traffic and industries, scenarios may also be studied with heavy emissions from accidents.
Ventilation - dimensioning and placing
When calculating natural ventilation and when designing ventilation systems, you need to know the pressure distribution of a building for different wind situations. When placing ventilation intakes, consideration must be given to the levels of air pollutants around the building, obtained through calculations of the spread from nearby emission sources.