ISSN:
1573-1472
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract The mean velocity and longitudinal turbulence-intensity distributions inside the zone of and above high roughness elements were investigated experimentally. This was accomplished by using a model forest canopy. The results indicate that the flow may be divided into transition and fully-developed flow regions, followed by a short adjustment distance near the downstream terminus of the rough boundary. The transition region has a strong effect on the flow characteristics within and above the layer of roughness elements. Generally, a similar qualitative variation for both velocity and turbulence was found inside and above the roughness zone, whose influence extends to more than three times the roughness height. Investigation of the modified universal logarithmic law for describing the velocity variation above the roughness zone revealed that both of the so-called similarity parameters, i.e., friction velocity and roughness length, are not local constants. On the contrary, for a given flow and local conditions they vary drastically with height. It is suspected that this is due to the fact that the classical assumption of constant shear stress throughout the boundary layer or significant portions of it is not satisfied in the case of roughness elements many times greater in height than the thickness of the viscous wall zone.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02186035
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