scope:

Wind-tunnel and water-channel investigations on (physical) models are methods commonly accepted to be suitable for finding answers to air-hygiene and micro-climate problems, and for the validation of numerical flow and dispersion models. The wind tunnel is particularly suited for investigations on areas with complex building or topographical structures. The good performance of physical modelling is mainly a result of the physical similarity of the simulation of the relevant flow and dispersion processes. This requires the modelling of the atmospheric boundary layer, and an appropriate test model.

This guideline is meant to implement standardised experimental techniques and quality assurance for laboratories investigating environmental issues. While the emphasis is put on wind-tunnel experiments, the essence of the statements made will also apply to water channels. This guideline supplies the users of such test facilities with specifications concerning experimental procedures, and indicates reference measurements and data records suitable for evaluation purposes. The fundamentals of flow mechanics and parameters of the atmospheric boundary layer, relevant to modelling, are described. Applications and limitations of physical model investigations are shown.

Problems of building aerodynamics are dealt with in a guide published by the Windtechnologische Gesellschaft e.V. (WTG, 1994).

This guideline deals with the physical modelling of

• flow fields and
• concentration fields
• on scales between several metres and several kilometres (microscale).

These investigation methods are specially used in cases where mechanically induced turbulence prevails, and which are not covered by existing standards and guidelines. This applies in particular to

• the dispersion of air contaminants in urban and industrial areas, and in orographically structured terrain,
• influences on the wind field resulting from adjoining further buildings to existing building areas.

Therefore, this guideline is restricted to the modelling of the well-mixed boundary layer.

Physical model experiments yield three-dimensional flow and concentration fields for the applications listed in Table 1.

The results obtained using the model can be related to the actual environmental situation by applying similarity laws.