The Influence of Slopes of Isolated Three-Dimensional Valleys on Near-Surface Turbulence

Motivated by a limited understanding of how valleys affect near-surface turbulence, characterizations of neutrally stable atmospheric-boundary-layer flows over isolated valleys are presented. In particular, the influence of the slopes of the three-dimensional ridges that form the idealized valleys a...

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Bibliographic Details
Published in:Boundary-layer meteorology 2022, Vol.182 (1), p.55-74
Main Authors: Freitas, Sylvio, Harms, Frank, Leitl, Bernd
Format: Article
Language:English
Subjects:
Atmospheric boundary layer
Atmospheric Protection/Air Quality Control/Air Pollution
Atmospheric Sciences
Boundary layer flow
Boundary layer winds
Earth and Environmental Science
Earth Sciences
Flow separation
Fluid dynamics
Influence
Investigations
Meteorology
Research Article
Ridges
Simulation
Slopes
Surface roughness
Turbulence
Turbulence intensity
Valleys
Velocity
Wind tunnels
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Summary:Motivated by a limited understanding of how valleys affect near-surface turbulence, characterizations of neutrally stable atmospheric-boundary-layer flows over isolated valleys are presented. In particular, the influence of the slopes of the three-dimensional ridges that form the idealized valleys are investigated. Flows over three distinct symmetric valley geometries were modelled in a large boundary-layer wind tunnel. For each valley geometry, the high-resolution measurements from the crests of each of the ridges and the midpoint between them are compared with an undisturbed moderately rough classed boundary-layer flow over flat terrain with homogeneous surface roughness. Flow separation originates above the crests of the first ridges of all geometries and generates recirculation zones. These are characterized by slope-dependent increases in three-dimensional near-surface turbulence when compared with the attached flows further upstream. The recirculation zones longitudinally extend to roughly half the valley width. Above the crests of the second ridges, the longitudinal velocity component decreases and turbulence intensity increases when compared with the flows above the crests of the first ridges. Results also exhibit significant increases of turbulence above the inner-valley regions of all geometries.
ISSN:0006-8314
1573-1472
DOI:10.1007/s10546-021-00648-8