Boundary-Layer Flow Over Complex Topography

Finnigan, John; Ayotte, Keith W.; Harman, Ian N.; Katul, Gabriel G.; Oldroyd, H. J.; Patton, Edward G.; Poggi, Davide; Ross, Andrew; Taylor, Peter A.

doi:10.1007/s10546-020-00564-3

Cited by 74 publications

(72 citation statements)

References 309 publications

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“…The resulting hydrodynamic variations are described by a linear theory that Jackson and Hunt [1] developed for wind profiles over low hills. Their work inspired analyses of laminar [2][3][4][5][6] and turbulent [7][8][9][10][11][12][13][14][15][16][17][18] flows on shallow bedforms, as recently reviewed by Finnigan et al [19]. Flow modulation associated with fluid-structure interactions also drives the dynamics of wind-driven wave generation at a liquid surface [20,21], or on compliant thin sheets [22][23][24], leading to the flag instability when a free end is allowed to flap [25].…”

Section: Introductionmentioning

confidence: 99%

Basal Pressure Variations Induced by a Turbulent Flow Over a Wavy Surface

2021

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Turbulent flows over wavy surfaces give rise to the formation of ripples, dunes and other natural bedforms. To predict how much sediment these flows transport, research has focused mainly on basal shear stress, which peaks upstream of the highest topography, and has largely ignored the corresponding pressure variations. In this article, we reanalyze old literature data, as well as more recent wind tunnel results, to shed a new light on pressure induced by a turbulent flow on a sinusoidal surface. While the Bernoulli effect increases the velocity above crests and reduces it in troughs, pressure exhibits variations that lag behind the topography. We extract the in-phase and in-quadrature components from streamwise pressure profiles and compare them to hydrodynamic predictions calibrated on shear stress data.

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Section: Introductionmentioning

confidence: 99%

Basal Pressure Variations Induced by a Turbulent Flow Over a Wavy Surface

2021

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“…The turbulent fluctuations also increase significantly in the presence of the hills. The increase in

σ_{\tilde{w}}

from Figure 2b to Figures 2d and 2f is apparent throughout the domain, with the largest increase located in the highly turbulent wake downwind of the hill crest (Finnegan et al., 2020; Kaimal & Finnigan, 1994). The r.m.s.…”

Section: Resultsmentioning

confidence: 98%

“…The turbulent fluctuations also increase significantly in the presence of the hills. The increase in   w from Figure 2b to Figures 2d and 2f is apparent throughout the domain, with the largest increase located in the highly turbulent wake downwind of the hill crest (Finnegan et al, 2020;Kaimal & Finnigan, 1994) u for the large hill in Figure 2f. The wake region behind the large hill extends across the periodic boundary and reaches the upwind region near  x 0.5 km.…”

Section: Vertical Flow Statisticsmentioning

confidence: 90%

Gentle Topography Increases Vertical Transport of Coarse Dust by Orders of Magnitude

et al. 2021

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Dust particles emitted in the atmosphere are responsible for numerous phenomena of global consequence here on Earth. In particular, coarse dust (with diameter greater than 5 μm) absorbs shortwave and longwave radiation which contributes to warming of the planet (Kok et al., 2017), redistributes mineral nutrients such as iron and phosphates to ocean (Jickells et al., 2014) and land ecosystems (Swap et al., 1992) through its long-range transport, and alters the nucleation of clouds and their subsequent precipitation (Mahowald & Kiehl, 2003).Given the importance of coarse dust to local and global processes, it is critical for models to accurately represent coarse dust concentrations. Yet there is a consistent disparity between measured observations and global dust models, where models severely underestimate the presence of coarse dust (Adebiyi &

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“…Investigations focused on flows over isolated valleys or double ridges are scarce when compared with studies centred on single hills or ridges (Finnigan et al 2020). The field campaign at Perdigão has provided analysis of specific properties of the flow (e.g., Menke et al 2018Menke et al , 2019Fernando et al 2019;Letson et al 2019).…”

Section: Introductionmentioning

confidence: 99%

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

Freitas¹,

Harms²,

Leitl³

2021

Boundary-Layer Meteorol

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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.

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Boundary-Layer Flow Over Complex Topography

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Cited by 74 publications

References 309 publications

Basal Pressure Variations Induced by a Turbulent Flow Over a Wavy Surface

Basal Pressure Variations Induced by a Turbulent Flow Over a Wavy Surface

Gentle Topography Increases Vertical Transport of Coarse Dust by Orders of Magnitude

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

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