دانلود رایگان مقاله لاتین تشکیل استریمربرف از سایت الزویر
عنوان فارسی مقاله:
تشکیل استریمرهای برف در لایه مرزی جو آشفته
عنوان انگلیسی مقاله:
The formation of snow streamers in the turbulent atmosphere boundary layer
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Drifting snow is a typical two-phase flow that frequently occurred at high latitudes and its studies are of glaciological and hydrological importance (Zhou et al., 2014). The drifting snow process carries snow grains from one place to another and results in a redistribution of snow cover. On one hand, the non-uniform distribution snow layer caused by drifting snow on mountains may induce and aggravate various natural geologic hazards (Michaux et al., 2001). On the other hand, drifting snow is one of the main causes of the temporal and spatial variation of snow distribution, contributes greatly to the mass balance of the ice sheets (Gallée et al., 2013). Thus, the dispersion and transport characteristics of snow particles in the turbulent boundary layer require in-depth research. Many drifting snow models have been proposed to investigate this comprehensive phenomenon. Most of them are two-fluid models assume snow particles a continuous phase (Uematsu et al., 1991; Mann et al., 2000; Taylor, 1998; Déry and Yau, 1999; Fukushima et al., 1999, 2001; Xiao et al., 2000; Bintanja, 2000a, 2000b; Gauer, 2001; Lehning et al., 2008; Schneiderbauer and Prokop, 2011; Vionnet et al., 2014). These models have greatly improved our understanding of drifting snow process. However, snow grains can also saltate downflow due to the gravitational effect. The movement of mid-air snow particles and the interaction between snow grains and turbulent structures are essential for understanding the natural drifting snow process and its spatial structure under the action of turbulent wind. In recent years, some Euler-Lagrange models have been explored to investigate the drifting snow process, in which the snow particles were tracked with Lagrange method. Nemoto and Nishimura (2004) studied 2-D snow particle motions in the 1-D turbulent boundary layer based on particle tracking with consideration of the aerodynamic entrainment and wind modification. Later, Zhang and Huang (2008) presented a steady state snow drift model and analyzed the features of the steady state of drifting snow. The studies on the dispersion of solid particles in the 3-D turbulent boundary layer based on Large Eddy Simulation (LES) have also been conducted by researchers. Vinkovic et al. (2006) studiedthe dispersion of solid particles in a turbulent boundary layer based on the large-eddy simulation combined with the dynamic Germano subgrid-scale (SGS) model, while the spatial structure of the sand flow was not discussed. Then, Dupont et al. (2013) simulated the wind-blown sand movement in the near surface turbulent flow layer and found the process of sand saltation is very intermittent in time and space due to the turbulence of the flow. Groot Zwaaftink et al. (2014) simulated the small-scale drifting snow in the turbulent boundary layer and analyzed the intermittency of drifting snow by simplifying the coupling effect between particles and wind field as a uniform roughness modification. This may be inaccurate since the saltating snow particles are nonuniform distributed in the turbulent flow. Huang and Wang (2015) performed the behaviors of snow particle in a fully developed turbulent boundary layer and snow streamers were reproduced. Up to now, the characteristic sizes of snow streamer and its formation mechanisms require further exploration. In addition, all above studies didn’t adopt an adequate SGS model to reflect the influence of non-uniform distributed saltation particles on the wind field, which will affect the final structure of the drifting snow to a great extent. Here, we investigate the influence of turbulent structures on saltating snow using a Lagrangian dynamic subgrid-scale (SGS) model (Meneveau et al., 1996). This model averages the Smagorinsky coefficient in time following fluid pathlines and can match the non-uniform drag force due to the saltating snow particles essentially. The coupling effect between snow particles and wind field is explicitly considered. Each saltating snow particle is tracked using a Lagrangian approach and a splash scheme is used to describe the grain-bed interactions. The development of drifting snow in the turbulent boundary layer with mixed grain size is numerically studied and ‘snow streamers’ in the turbulent boundary layer are reproduced. The most important improvement of this model is that the reaction force of each saltating particle is calculated and imposed on the wind field and each single particle is tracked separately in order to obtain the detail structure of blown snow in the turbulent boundary layer. The spatial distribution characteristic of snow streamers and its relevance with turbulent wind structure are analyzed in detail.
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کلمات کلیدی:
The Formation of Snow Crystals » American Scientist www.americanscientist.org › PAST ISSUE › January-February 2007 by K Libbrecht - Cited by 18 - Related articles FEATURE ARTICLE. The Formation of Snow Crystals. Subtle molecular processes govern the growth of a remarkable variety of elaborate ice structures. [PDF]The Formation of Snow Crystals citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.687.1381&rep=rep1... by KG Libbrecht - 2007 - Cited by 18 - Related articles The Formation of Snow Crystals. Subtle molecular processes govern the growth of a remarkable variety of elaborate ice structures. Kenneth G. Libbrecht. [PPT]Snow Formation - Atmospheric Sciences at UNBC cirrus.unbc.ca/454/week2/Week2_2013.ppt The formation of snow requires at least 3 conditions: 1) atmospheric moisture and 2) mechanisms to convert this water vapour into precipitation (i.e. vertical ... Searches related to formation of snow how cold does it need to be to snow at what temperature does it snow in celsius how is sleet formed what temperature does it have to be to snow highest temperature for snow snow temperature range how cold does it have to be to snow celsius can it be too cold to snow
