Problems of atmospheric shear flows and their laboratory simulation

Shear flows generated by movement of the atmosphere near the earth's surface are accompanied by complexities not ordinarily encountered in the treatment of turbulent boundary layers. Problems arising from the following physical features are considered:

1. thermal stratification;
2. surface roughness in the form of forests and cities;
3. non-uniformity of surface roughness and/or temperature (leading to 3-dimensional turbulent boundary layers);
4. surface irregularities in the form of hilly and mountainous topography.

The complex nature of atmospheric shear flows has stimulated efforts to study their characteristics in the laboratory under controlled conditions. Accordingly, questions of similarity between the laboratory and the atmospheric flows for both mean and turbulent quantities arise. Similarity criteria, or appropriate scaling relationships, are discussed. Wind tunnels designed for investigations related to atmospheric shear flows are described. These facilities are shown to have a capability for simulating such flows for a wide range of the physical features listed above.