logarithmic velocity profile
Near aerodynamically smooth surfaces, the result is
that is, the logarithmic velocity profile, where u*
is the friction velocity
and ν the kinematic viscosity
≅ 0.4 and has been called the Kármán constant or von Kármán's constant
. The equation fails for a height z
sufficiently close to the surface. For aerodynamically rough flow, molecular viscosity
becomes negligible. The profile is then z0
is a constant related to the average height ε of the surface irregularities by z0
= ε/30 and is called the aerodynamic roughness length
. Another derivation of the logarithmic profile was obtained by Rossby under the assumption that for fully rough flow the roughness affects the mixing length
only in the region where z
are comparable. Then l
For statically nonneutral conditions, a stability
correction factor can be included (see
equation in definition of aerodynamic roughness length
Haugen, D. A. 1973. Workshop on Micrometeorology. Amer. Meteor. Soc., . 392 pp.
Sutton, O. G. 1953. Micrometeorology. sect. 3.9.
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