Measurements and one-dimensional model calculations of snow transport over a mountain ridge

AbstractWind transport of snow can cause an additional snow load on leeward slopes, which often has a considerable influence on avalanche danger. For a quantitative assessment of this process, a model is proposed which calculates the snow transport over a two-dimensional mountain ridge, based on input measurements of wind speed and precipitation. Since the topography is idealized, the model is focused on the snow mass that is transported over the ridge, and no statements are made about the exact snow distribution over the slopes. Three transport modes are distinguished: snow transport in saltation, snow transport in Suspension, and preferential deposition of precipitation. Suspension is modelled with a one-dimensional diffusion equation, and for the saltation layer a newly developed model, based on the microscale physical processes, is implemented. The effect of speed-up of the wind over the ridge is included by assuming an analytical wind profile with a maximum wind speed at a few meters above the ridge Advective effects are taken into account in a parameterization of the turbulent shear stress profile. The model is compared with measurements taken at the experimental snowdrift site Gaudergrat in the Parsenn area, Switzerland, and good agreement is obtained between calculated and measured results.

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Turbulent shear stress measurements in the vicinity of aortic heart valve prostheses

Journal of Biomechanics ◽

10.1016/0021-9290(86)90020-5 ◽

1986 ◽

Vol 19 (6) ◽

pp. 433-442 ◽

Cited By ~ 95

Author(s):

Ajit P. Yoganathan ◽

Yi-Ren Woo ◽

Hsing-Wen Sung

Keyword(s):

Shear Stress ◽

Heart Valve ◽

Turbulent Shear ◽

Stress Measurements ◽

Heart Valve Prostheses ◽

Aortic Heart Valve ◽

Turbulent Shear Stress ◽

Valve Prostheses

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Impact of fluid turbulent shear stress on failure surface of reservoir bank landslide

Arabian Journal of Geosciences ◽

10.1007/s12517-018-4030-4 ◽

2018 ◽

Vol 11 (22) ◽

Author(s):

Xuan Zhang ◽

Liang Chen ◽

Faming Zhang ◽

Chengteng Lv ◽

Yi feng Zhou

Keyword(s):

Shear Stress ◽

Failure Surface ◽

Turbulent Shear ◽

Turbulent Shear Stress

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Effects of Concave Curvature on Boundary Layer Transition Under High Free-Stream Turbulence Conditions

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/2001-gt-0191 ◽

2001 ◽

Cited By ~ 3

Author(s):

Michael P. Schultz ◽

Ralph J. Volino

Keyword(s):

Boundary Layer ◽

Free Stream ◽

Turbulent Transport ◽

Boundary Layer Transition ◽

Transitional Flow ◽

Turbulent Shear ◽

Radius Of Curvature ◽

Layer Transition ◽

Free Stream Turbulence ◽

Turbulent Shear Stress

An experimental investigation has been carried out on a transitional boundary layer subject to high (initially 9%) free-stream turbulence, strong acceleration K=ν/Uw2dUw/dxas high as9×10-6, and strong concave curvature (boundary layer thickness between 2% and 5% of the wall radius of curvature). Mean and fluctuating velocity as well as turbulent shear stress are documented and compared to results from equivalent cases on a flat wall and a wall with milder concave curvature. The data show that curvature does have a significant effect, moving the transition location upstream, increasing turbulent transport, and causing skin friction to rise by as much as 40%. Conditional sampling results are presented which show that the curvature effect is present in both the turbulent and non-turbulent zones of the transitional flow.

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Contribution towards a Reynolds-stress closure for low-Reynolds-number turbulence

Journal of Fluid Mechanics ◽

10.1017/s0022112076001961 ◽

1976 ◽

Vol 74 (4) ◽

pp. 593-610 ◽

Cited By ~ 261

Author(s):

K. Hanjalić ◽

B. E. Launder

Keyword(s):

Reynolds Number ◽

Shear Stress ◽

Reynolds Stress ◽

Dissipation Rate ◽

Numerical Solutions ◽

Low Reynolds Number ◽

Transport Processes ◽

Turbulent Shear ◽

Turbulent Shear Stress ◽

Low Reynolds

The problem of closing the Reynolds-stress and dissipation-rate equations at low Reynolds numbers is considered, specific forms being suggested for the direct effects of viscosity on the various transport processes. By noting that the correlation coefficient$\overline{uv^2}/\overline{u^2}\overline{v^2} $is nearly constant over a considerable portion of the low-Reynolds-number region adjacent to a wall the closure is simplified to one requiring the solution of approximated transport equations for only the turbulent shear stress, the turbulent kinetic energy and the energy dissipation rate. Numerical solutions are presented for turbulent channel flow and sink flows at low Reynolds number as well as a case of a severely accelerated boundary layer in which the turbulent shear stress becomes negligible compared with the viscous stresses. Agreement with experiment is generally encouraging.

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Conditional Sampling in a Transitional Boundary Layer Under High Freestream Turbulence Conditions

Journal of Fluids Engineering ◽

10.1115/1.1521957 ◽

2003 ◽

Vol 125 (1) ◽

pp. 28-37 ◽

Cited By ~ 28

Author(s):

Ralph J. Volino ◽

Michael P. Schultz ◽

Christopher M. Pratt

Keyword(s):

Boundary Layer ◽

Shear Stress ◽

Streamwise Velocity ◽

Turbulent Shear ◽

Conditional Sampling ◽

Freestream Turbulence ◽

Mean Velocity ◽

Transitional Boundary Layer ◽

Turbulent Shear Stress ◽

Order Of Magnitude

Conditional sampling has been performed on data from a transitional boundary layer subject to high (initially 9%) freestream turbulence and strong (K=ν/U∞2dU∞/dx as high as 9×10−6) acceleration. Methods for separating the turbulent and nonturbulent zone data based on the instantaneous streamwise velocity and the turbulent shear stress were tested and found to agree. Mean velocity profiles were clearly different in the turbulent and nonturbulent zones, and skin friction coefficients were as much as 70% higher in the turbulent zone. The streamwise fluctuating velocity, in contrast, was only about 10% higher in the turbulent zone. Turbulent shear stress differed by an order of magnitude, and eddy viscosity was three to four times higher in the turbulent zone. Eddy transport in the nonturbulent zone was still significant, however, and the nonturbulent zone did not behave like a laminar boundary layer. Within each of the two zones there was considerable self-similarity from the beginning to the end of transition. This may prove useful for future modeling efforts.

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Abstract 329: The Role of TIE1 in Flow Mediated Lymphatic Vessel Remodeling and Valvulogenesis

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.36.suppl_1.329 ◽

2016 ◽

Vol 36 (suppl_1) ◽

Author(s):

Cristina Harmelink ◽

Bin Zhou ◽

Xianghu Qu ◽

H. Scott Baldwin

Keyword(s):

Network Formation ◽

Lymphatic Vessels ◽

Mechanical Stimulus ◽

Turbulent Shear ◽

Branch Points ◽

Turbulent Shear Stress ◽

Valve Development ◽

Lymphatic Vasculature ◽

Cellular Machinery ◽

Molecular Landscape

Recently, it has been shown that the mechanical stimulus of turbulent shear stress caused by onset of lymph flow is required for lymphatic remodeling, maturation, and lymphatic valve (LV) development. Homeostasis of the adult lymphatic vasculature also relies on flow-mediated signal transduction. However, the cellular machinery responsible for transducing mechanosensory signals required for lymphatic network formation and maintenance is unknown. Our laboratory has previously shown that TIE1 is at least partially responsible for mechanotransduction of turbulent flow required for initiation and maintenance of atherosclerotic plaque formation at the branch points of systemic vasculature in the adult animal. Moreover, TIE1 is expressed throughout lymphatic vasculature during mouse embryogenesis into adulthood, with enrichment in LVs. To circumvent the embryonic lethality caused by global Tie1 disruption, we conditionally deleted Tie1 using Nfatc1Cre. Nfatc1Cre drives recombination in lymphatic endothelial cells, with strong expression in the LVs. Nfatc1Cre:Tie1fl/fl mutants survive to birth but accumulate chyle in the peritoneal and pleural cavities by postnatal day 2. The lymphatic vessels in the mutants are dilated and tortuous, and do not undergo normal hierarchical remodeling. The constrictions that normally indicate intraluminal valve development are lacking in the mutant lymphatic vessels. Underlying these defects in the Nfatc1Cre:Tie1fl/fl mutants is loss of the normal molecular landscape associated with lymphatic patterning and valvulogenesis. Therefore, we hypothesize that Tie1 orchestrates the mechanotransduction necessary for intraluminal LV development and postnatal maintenance.

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Quantitative Spectroscopy of Wolf-Rayet Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100093611 ◽

1988 ◽

Vol 108 ◽

pp. 133-140

Author(s):

W. Schmutz

Keyword(s):

Representative Point ◽

Dimensional Model ◽

Model Calculations ◽

One Dimensional ◽

The Past ◽

First Results ◽

The One ◽

Expanding Atmospheres ◽

New Generation ◽

The Continuum

Advances in theoretical modeling of rapidly expanding atmospheres in the past few years made it possible to determine the stellar parameters of the Wolf-Rayet stars. This progress is mainly due to the improvement of the models with respect to their spatial extension: The new generation of models treat spherically-symmetric expanding atmospheres, i.e. the models are one-dimensional. Older models describe the wind by only one representative point. The older models are in fact ‘core-halo’ approximations. They have been introduced by Castor and van Blerkom (1970), and were extensively employed in the past (cf. e.g. Willis and Wilson, 1978; Smith and Willis, 1982). First results from new one-dimensional model calculations are published by Hillier (1984), Schmutz (1984), Hamann (1985), Hillier (1986), and Schmutz et al. (1987a); more detailed results are presented by Schmutz and Hamann (1986), Hamann and Schmutz (1987), Hillier (1987a,b), Wessolowski et al. (1987), Hillier (1987c) and Hamann et al. (1987). These results demonstrate that the step from zero- to one-dimensional calculations is essential. The important point is that the complicated interrelation between NLTE-level populations and radiation field is treated adequately (Schmutz and Hamann, 1986; Hillier, 1987). For this interrelation it is crucial to model consistently not only the line-formation region, but also the layers where the continuum is emitted. In fact, it is the core-halo approximation that causes the one-point models to fail in certain aspects.

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