Air Flow Over Complex Terrain

Finnigan, John

doi:10.1007/978-3-642-73845-6_13

Cited by 39 publications

(36 citation statements)

References 53 publications

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“…For example, on the hill top, R is negative since the centre of curvature of the streamlines lies in the negative z direction. In the streamline system, the mean continuity equation is trivial and is replaced by a geometric identity between R and L, (Finnigan, 1988): a,($$+a,(;)-;=o.…”

Section: Equations Of Motion In the Streamline Coordinate Systemmentioning

confidence: 99%

“…Available field and wind-tunnel data reviewed by Finnigan (1988) show that on smooth, symmetrical, two-dimensional ridges, the critical slope angle for steady separation is around 20" but that separation will occur on hills less steep than this if the surface is rough. For example, on a wind-tunnel model hill of similar profile to the present one but with a maximum slope angle of 16" and covered with a model plant canopy that produced a value h/z0 = 50, a steady separation bubble extended about 2h downwind of the crest (unpublished work by J. J. Finnigan, M. R. Raupach, and Y. Brunet).…”

Section: The Wake Regionmentioning

confidence: 99%

“…Australia. Moreover, many wind-tunnel experiments have in fact been performed; a recent review by Finnigan (1988) lists fifteen wind tunnel simulations and ten field experiments between 1978 and 1985. The reasons for the lack of reliance on wind-tunnel data must evidently be compelling.…”

Section: Introductionmentioning

confidence: 99%

“…This is presently an area of active research. Another response, the one taken in this paper, is to stay with fully rough models and point out that these in any case represent a situation of practical importance: hills covered with tall vegetation Finnigan, 1988). The evolution of the most recent ideas on boundary-layer flow over hills is examined from two different perspectives in the recent reviews by and Finnigan (1988).…”

Section: Introductionmentioning

confidence: 99%

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A wind tunnel study of turbulent flow over a two-dimensional ridge

Finnigan

Raupach

Bradley

et al. 1990

Boundary-Layer Meteorol

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105

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We present a wind-tunnel simulation of adiabatic atqospheric flow normal to a rough, twodimensional ridge. The data are analyzed in physical streamline coordinates, which are described in some detail. The mean velocity speed-up on the hill top is adequately predicted by existing formulae while the behaviour of the wake flow fits into a pattern that emerges from other wind-tunnel experiments. The turbulent stresses evolve in response to the extra strain rates induced by the hill, streamline curvature and acceleration: 3 is coupled strongly to acceleration while z and 7 follow curvature. These differing responses lead to significant phase differences between the changes in the component stresses as the hill is traversed. An analogous response is seen in the components of turbulent stress divergence, which are computed as part of streamwise momentum budgets. Only very close to the surface is turbulent stress divergence comparable to the inertial and pressure terms in the momentum budget; over most of the flow regime, the mean flow response is approximately inviscid. Finally, we compare our results with data from other wind tunnel models and from real hills.

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Section: Equations Of Motion In the Streamline Coordinate Systemmentioning

confidence: 99%

Section: The Wake Regionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A wind tunnel study of turbulent flow over a two-dimensional ridge

Finnigan

Raupach

Bradley

et al. 1990

Boundary-Layer Meteorol

Self Cite

105

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“…The comparison with Zeman and Jensen's model is quite good between 8 and 16m and again at 50m. Finnigan (1988) showed that streamline curvature has a stabilizing influence on turbulence, implying a reduction in stress, over the crest of a hill. Although MSFD does not incorporate effects of streamline curvature, its comparison with data at 8 m and above is about as good as the Zeman-Jensen model, which &es include those effects.…”

Section: Effect Of Increased Vertical Resolution In Msfd Outputmentioning

confidence: 99%

Shear stress results from a mixed spectral finite-difference model: Application to the Askervein Hill project data

Walmsley

Padro

1990

Boundary-Layer Meteorol

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Beljaars et al. (1987) developed a model for neutrally stratified boundary-layer flow over roughness changes and topography. It has been discovered that a constant parameter. LI, was missing in the algebraic-stress closure equations of their paper. This omission also occurred in the MSFD model code but only affects the Askervein Hill shear-stress results for the E--E-T turbulence closure in Beljaars et al. It also changes the stress results of Karpik (1988). but not his conclusions regarding the robustness of his improved numerical scheme. The present paper demonstrates the effect of the omission of the parameter, a, and tests the sensitivity of the model to variations in its value. The new results are compared with the data and model results of Zeman and Jensen (1987).

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Aeolian processes across transverse dunes. I: Modelling the air flow

Boxel

Arens

Dijk

1999

Earth Surf. Process. Landforms

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This paper discusses a two-dimensional second-order closure model simulating air flow and turbulence across transverse dunes. Input parameters are upwind wind speed, topography of the dune ridge and surface roughness distribution over the ridge. The most important output is the distribution of the friction velocity over the surface. This model is dynamically linked to a model that calculates sand transport rates and the resulting changes in elevation. The sand transport model is discussed in a separate paper.The simulated wind speeds resemble patterns observed during field experiments. Despite the increased wind speed over the crest, the friction velocity at the crest of a bare dune is reduced compared to the upstream value, because of the effect of stream line curvature on turbulence. These curvature effects explain why desert dunes can grow in height. In order to obtain realistic predictions of friction velocity it was essential to include equations for the turbulent variables in the model. In these equations streamline curvature is an important parameter.The main flaw of the model is that it cannot deal with flow separation and the resulting recirculation vortex. As a result, the increase of the wind speed and friction velocity after a steep dune or a slipface will be too close to the dune foot. In the sand transport model this was overcome by defining a separation zone.

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Air Flow Over Complex Terrain

Cited by 39 publications

References 53 publications

A wind tunnel study of turbulent flow over a two-dimensional ridge

A wind tunnel study of turbulent flow over a two-dimensional ridge

Shear stress results from a mixed spectral finite-difference model: Application to the Askervein Hill project data

Aeolian processes across transverse dunes. I: Modelling the air flow

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