Problems of atmospheric shear flows and their laboratory simulation

Abstract

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.

Development of an experimental approach to study coupled soil‐plant‐atmosphere processes using plant analogs

“…Intermediate‐scale experimentation was originally introduced in the early 1990s and has been extensively adopted at CESEP for studying the fate and transport behavior of nonaqueous phase liquids [e.g., Illangasekare et al ., ; Barth et al ., ; Moreno‐Barbero and Illangasekare , ] and CO 2 leakage, exsolution, and trapping [e.g., Plampin et al ., ; Trevisan et al ., ; Agartan et al ., ]. According to the definition provided above, wind tunnel testing can also be considered a form of intermediate‐scale testing; wind tunnels have historically been employed in the investigation of the atmospheric boundary layer development [e.g., Cermak and Arya , ; Cermak , ; Burton , ], atmospheric gas dispersion [e.g., Meroney and Neff , ; Michioka et al ., ], and wind erosion of soils and dune formation [e.g., Bagnold , ; Gabriels et al ., ]. Haghighi and Or [, ] and Trautz [], among others, have further demonstrated that intermediate‐scale experimentation can be adopted with great success for studying a class of problems related to coupled porous media‐free flow systems (e.g., bare‐soil evaporation).…”

Numerical and wind tunnel modeling on the windbreak effectiveness to control the aeolian erosion of conical stockpiles

“…Among others, it is desirable to reproduce the wind profile in the test section. Cermak and Arya [14], like other authors, state that "to satisfy, even approximately, the various criteria of similarity between atmospheric shear flows and simulated flows in wind tunnels, thick turbulent boundary layers with large turbulence intensities are required". To appropriately model the boundary layer in a wind tunnel, a long roughened surface would be necessary.…”

Large-Eddy Simulation of the Evolving Stable Boundary Layer Over Flat Terrain

“…It is di cult to apply the results of laboratory experiments, conducted in controlled conditions, to the complex conditions found in the PBL. Indeed the PBL does not usually have a w ell-de ned outer edge, as do laboratory ows (Cermak and Arya, 1970). Laboratory conditions may allow study of selected processes at low Reynolds number.…”