P&K 3781 (VDI 3781 2)
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Calculation of the stack height according to TA Luft 1986/2002
with regard to rugged terrain according to
VDI 3781 Part 2
Translated extract of VDI 3781 Part 2 published by
Dispersion of Pollutants in the Atmosphere
Stack heights with regard to rugged terrain
The known calculation procedures of the minimum stack height according to  are valid for flat terrain only. The purpose of the present Guideline VDI 3781 Part 2 is to extend the calculation procedure to rugged terrain. Therefore it replaces the draft VDI 2289 Part 3, edition 10.69.
To determine the correction, the geometry of the terrain and the conformity to the Science of flow are to be considered.
The theory based on this Guideline is fully described in the work of Stümke .
In derivation of this theory the following is assumed:
- easy to categorize long drawn-out elevation or depression,
- flat stationary Zone of flow vertically to the elevation or depression.
- Streamline motion in greater distance to the ground,
- Determination of the wind velocity in the layers near the ground of the relating streamline motion by formal transfer of the case of absent ground disturbance.
- Use of a simplified fixed form of the diffusion equation according to Fick with constant coefficients.
These conditions, according to the current state of knowledge, are necessary for a survey of the problem dealt with in this Guideline. However, according to terrain and climatic conditions of location, in reality the conditions serve its purposes roughly. Considering the climatic conditions, smaller stack heights may result than those calculated according to this Guideline.
In cases where this Guideline is not to be used, because of the conditions mentioned in the theory, an expert for dispersion should be consulted.