The near-neutral atmospheric surface layer: turbulence and non-stationarity

Abstract

The neutrally stable atmospheric surface layer is used as a physical model of a very high Reynolds number, canonical turbulent boundary layer. Challenges and limitations with this model are addressed in detail, including the inherent thermal stratification, surface roughness and non-stationarity of the atmosphere. Concurrent hot-wire and sonic anemometry data acquired in Utah's western desert provide insight to Reynolds number trends in the axial velocity statistics and spectra.

Small wind turbines in turbulent (urban) environments: A consideration of normal and Weibull distributions for power prediction

“…When one also considers the propensity for strong winds across Dublin city, one can assume a neutral atmosphere at both sites considered here, where the majority of turbulent air flow is manifested mechanically. This position is consistent with the research carried out by Metzger and McKeon [14] where they demonstrate that in neutral environments, surface roughness dominates turbulence production. The authors further suggest that in the consideration of wind flow and turbulence, the wind resource is dependent on the mechanical effects of surface roughness.…”

“…From a wind resource perspective topography, the building morphology and the roughness length of the urban surface, 0 z , are the significant parameters to be considered when assessing the turbulent structure of air masses [14][15][16]. The factitious nature of the urban topography is discussed by Fernando in [17] and fluid dynamic analyses performed in [18] describes the complexity associated with the urban topography as being the rule governing the wind resource.…”

On the asymptotic state of high Reynolds number, smooth-wall turbulent flows

“…Their Figure 1 shows good support for (5) 10 12 ) have also been obtained using LES. 7 An immediate consequence of (5) is that 2 , and so both vanish asymptotically.…”

“…Research to achieve extremely large outer-scale Reynolds numbers, Re = U o /ν, where U o is an outer-scale velocity, is the outer length scale, and ν is the kinematic viscosity, has either made large, as in the surface layer turbulence and environmental science test (SLTEST) experiments 2 and in long working-section wind-tunnels 3 or has reduced ν while holding fixed, as in the super-pipe experiments. 4 In practice, the experimental search for high-Reynolds number, wall-bounded turbulence will generally encounter wall roughness.…”

Applicability of the Bulk-Transfer Approach to Estimate Evapotranspiration from Boreal Peatlands

“…The most remarkable feature is the recurrence of near-neutral stratification conditions defined by jz/Lj , 0:1 at the three field sites. This threshold has been used in several other studies (Högström 1988;Mahrt et al 2001;Novick et al 2004;Grachev et al 2007;Metzger et al 2007). The Necopastic, Mer Bleue, and Western Peatland sites are under near-neutral conditions 76%, 43%, and 40% of the time, respectively, mostly during daytime.…”