Führer durch die Strömungslehre

Prandtl, L.; Oswatitsch, Klaus; Wieghardt, Karl

doi:10.1007/978-3-322-99491-2

Cited by 184 publications

(137 citation statements)

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“…4a, b). Prandtl's (1944) analytical slope-wind model predicts shallower slope winds for steeper slopes and higher static stability of the background atmosphere. This is in agreement with our simulations in which the background stability and the slope angle are higher over the slope of the main ridge than over the slopes of the first ridge.…”

Section: Flow Structurementioning

confidence: 95%

The impact of embedded valleys on daytime pollution transport over a mountain range

2015

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Abstract. Idealized large-eddy simulations were performed to investigate the impact of different mountain geometries on daytime pollution transport by thermally driven winds. The main objective was to determine interactions between plain-to-mountain and slope wind systems, and their influence on the pollution distribution over complex terrain. For this purpose, tracer analyses were conducted over a quasitwo-dimensional mountain range with embedded valleys bordered by ridges with different crest heights and a flat foreland in cross-mountain direction. The valley depth was varied systematically. It was found that different flow regimes develop dependent on the valley floor height. In the case of elevated valley floors, the plain-to-mountain wind descends into the potentially warmer valley and replaces the opposing upslope wind. This superimposed plain-to-mountain wind increases the pollution transport towards the main ridge by an additional 20 % compared to the regime with a deep valley. Due to mountain and advective venting, the vertical exchange is 3.6 times higher over complex terrain than over a flat plain. However, the calculated vertical exchange is strongly sensitive to the definition of the convective boundary layer height. In summary, the impact of the terrain geometry on the mechanisms of pollution transport confirms the necessity to account for topographic effects in future boundary layer parameterization schemes.

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Section: Flow Structurementioning

confidence: 95%

The impact of embedded valleys on daytime pollution transport over a mountain range

2015

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“…From the pointwise perspective, the basic physics of fluid flow over a heated or cooled slope is described by the 1942 Prandtl model [87][88][89]. This is a closed-form solution of the Navier-Stokes equations, providing slope-normal profiles of equilibrium laminar flow over homogeneous slopes.…”

Section: Pointwise Perspective On Upslope Windsmentioning

confidence: 99%

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

et al. 2018

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Abstract:The exchange of heat, momentum, and mass in the atmosphere over mountainous terrain is controlled by synoptic-scale dynamics, thermally driven mesoscale circulations, and turbulence. This article reviews the key challenges relevant to the understanding of exchange processes in the mountain boundary layer and outlines possible research priorities for the future. The review describes the limitations of the experimental study of turbulent exchange over complex terrain, the impact of slope and valley breezes on the structure of the convective boundary layer, and the role of intermittent mixing and wave-turbulence interaction in the stable boundary layer. The interplay between exchange processes at different spatial scales is discussed in depth, emphasizing the role of elevated and ground-based stable layers in controlling multi-scale interactions in the atmosphere over and near mountains. Implications of the current understanding of exchange processes over mountains towards the improvement of numerical weather prediction and climate models are discussed, considering in particular the representation of surface boundary conditions, the parameterization of sub-grid-scale exchange, and the development of stochastic perturbation schemes.

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“…Diffusion-induced flows form the basis for a variety of physical processes, including mineral transport in rocks [1], the melting of icebergs [2], the migration of tectonic plates [3], the processes of transport and mixing of passive substances, the formation of intensive valley and mountain winds in a stably stratified atmosphere [4] and density flows in the ocean [5].…”

Section: Introductionmentioning

confidence: 99%

“…The first mathematical model of diffusion-induced flows was created in the middle of the past century with application to the problem on mountain and valley winds [4]. The marked universality mechanism of hillside flows formation both in the stratified atmosphere and the ocean [1,7] restored the interest in the problem after a long pause.…”

Section: Introductionmentioning

confidence: 99%

“…The marked universality mechanism of hillside flows formation both in the stratified atmosphere and the ocean [1,7] restored the interest in the problem after a long pause. In the pioneering theoretical investigations of diffusion-induced flows the stationary solutions were obtained in the infinite plate approximation on the basis of a linearized system of equations [4]. For constant slope, and assuming along-slope flow that is a function only of the wall-normal coordinate (that is, unidirectional flow), the velocity profile for a steady diffusion-induced flow is …”

Section: Introductionmentioning

confidence: 99%

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Modeling of Molecular Diffusion in Non-Homogeneous Media

Zagumennyi

2017

Research Bulletin of the National Technical University of Ukraine "Kyiv Politechnic Institute"

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Background. Due to combined effects of medium inhomogeneity and action of external forces, i.e. Earth's gravitation, electro-magnetic forces, global rotation, etc., a number of specific fluid motions appear in the environmental and life systems even in absence of pure mechanical reasons. Among them are so called diffusion-induced flows which always exist around obstacles with arbitrary geometry due to breaking of natural molecular flux of a stratifying agent on an impermeable surface. Objective. The aim of the paper is to analyze numerically a diffusion induced flow structure and dynamics around motionless obstacles immersed into a stably stratified medium, including a sloping plate, a wedge-shaped obstacle, a disc, and a circular cylinder. The numerical results obtained are compared with the available analytical and experimental data. Methods. The problem is solved numerically using two different algorithms based on the finite difference and finite volume methods. The first approach is implemented in the specially developed Fortran program codes, and the second one is based on the open source package OpenFOAM with the use of C programming language for developing special own solvers, libraries, and utilities, which enable solving the problems under consideration. Results. The numerical simulation reveals a complex multi-level vortex system of compensatory circulating flows around a motionless obstacle, which structure is strongly dependent on its position relative to the horizon. The most intensive and extended high-gradient horizontal interfaces attached to sharp edges or poles of obstacles are clearly observed in the numerical computations and laboratory experiments. Diffusion-induced flows form intensive pressure deficiency zones around an obstacle, which may lead to generation of propulsion mechanism resulting in self-movement of neutral buoyancy bodies in a continuously stratified fluid, e.g. horizontal movement of a wedge, rotation of a sloping plate, etc. Conclusions. Diffusion-induced flows are a wide-spread phenomenon in biology, medicine, and environmental systems, since such flows inevitably occur in any inhomogeneous media, including different solutions, suspensions, mixtures, etc. A complex multilevel vortex structure of diffusion-induced flows on an obstacle becomes even more complicated due to self-motion of the obstacle itself and displacement of various admixtures, suspended particles, additives, etc., which are always present in the real systems.

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Führer durch die Strömungslehre

Cited by 184 publications

References 0 publications

The impact of embedded valleys on daytime pollution transport over a mountain range

The impact of embedded valleys on daytime pollution transport over a mountain range

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

Modeling of Molecular Diffusion in Non-Homogeneous Media

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