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A large-eddy simulation (LES) with a one-equation subgrid-scale (SGS) model was developed to investigate the flow field and
pollutant dispersion inside street canyons of high aspect ratio (AR). A 1/7th power-law wall model was implemented near rigid
walls to mitigate the demanding near-wall resolution requirements in LES. This LES model had been extensively validated against
experimental results for street canyons of AR = 1 and 2 before it was applied to the cases of AR = 3 and 5. A ground-level
passive pollutant line source, located in the middle of the street, was used to simulate vehicular emissions. Three and five
vertically aligned primary recirculations were developed in the street canyons of AR 3 and 5, respectively. The ground-level
mean wind speed was less than 0.5% of the free stream value, which makes it difficult for the pollutant to be transported
upward for removal. High pollutant concentration and variance were found near the buildings where the air flow is upwards.
It was found that the velocity fluctuation, pollutant concentration and variance were all closely related to the interactions
between the primary recirculations and/or the free surface layer. Several quantities, which are non-linear functions of AR,
were introduced to quantify the air quality in street canyons of different configurations. 相似文献
2.
基于SGS的城市地理信息公共平台建设及应用 总被引：1，自引：1，他引：0
依托城市基础测绘成果数据,按照<地理信息公共服务平台>、<地理空间框架基本规定>等相关标准及规范,经过数据提取、重组、加工并制作了面向政务服务的地图产品数据;基于超图数字城市地理信息公共服务平台SGSV6.0,快速搭建了广州市政务基础地理信息共享服务平台,使得政府部门可以通过在线浏览、简单系统定制、地图API接口开发和... 相似文献
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Drilling through shale layers is associated with many problems such as wellbore instability, hole wash out, pipe stuck, etc. Reactive shale with swelling potential can lead to such problems. Reactive shale is a shale that has high swelling clay mineral like montmorillonite although there was a little amount of this clay mineral. So determine the type of clay mineral in shale formation and obtain the distribution of swellable clay mineral can help us in the selection of stable well path and determination of well location that has least instability problem, prevention and prediction of problem associated with swelling clay mineral such as pipe stuck, hole wash out, bit balling, etc. In this paper, we used thorium and potassium from corrected gamma ray (CGR) log to obtain the type and percentage of clay mineral. Then used X-ray diffraction for more detail analysis of clay mineral constitute. Finally, geostatistical modelling is used to obtain the continuity of clay mineral in the reservoir and estimate the amount of desire clay mineral along the reservoir. 相似文献
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对流边界层的大涡模拟研究 总被引：5，自引：0，他引：5
本文建立了一个均匀平坦地面上对流边界层的大涡模式,模式考虑了水汽,采用了考虑浮力和固壁影响订正的一阶闭合。并用所建模式进行了由热扰动发展的对流边界层的模拟及其对地表热状况变化响应的初步探讨性模拟工作。通过模拟认为,模式较好地反映了对流边界层的主要结构。 相似文献
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This present paper proposes a two-dimensional lattice Boltzmann model coupled with a Large Eddy Simulation (LES) model and applies it to flows around a non-submerged groyne in a channel. The LES of shallow water equations is efficiently performed using the Lattice Boltzmann Method (LBM) and the turbulence can be taken into account in conjunction with the Smagorinsky Sub-Grid Stress (SGS) model. The bounce-back scheme of the non-equilibrium part of the distribution function is used to determine the unknown distribution functions at inflow boundary, the zero gradient of the distribution function is set normal to outflow boundary to obtain the unknown distribution functions here and the bounce-back scheme, which states that an incoming particle towards the boundary is bounced back into fluid, is applied to the solid wall to ensure non-slip boundary conditions. The initial flow field is defined firstly and then is used to calculate the local equilibrium distributions as initial conditions of the distribution functions. These coupled models successfully predict the flow characteristics, such as circulating flow, velocity and water depth distributions. The comparisons between the simulated results and the experimental data show that the model scheme has the capacity to solve the complex flows in shallow water with reasonable accuracy and reliability. 相似文献
6.
Yongcun Zhao Xianghua Xu Biao Huang Weixia Sun Xuexin Shao Xuezheng Shi Xinling Ruan 《Environmental Geology》2007,52(7):1423-1433
A total of 540 topsoil samples (0–15 cm), 188 subsoil samples (20–40 cm), and four individual soil profiles were collected
in this study for mapping the Cu- and Pb-contaminated areas in soils of Zhangjiagang city, an industrialized city in the Yangtze
River Delta region of China. Robust geostatistical methods were applied for identifying possible spatial outliers of Cu and
Pb data, and then a sequential Gaussian simulation was employed for delineating the potential areas where Cu or Pb concentration
was affected by diffuse pollution. The results showed that the spatial outliers of Cu and Pb were strongly associated with
various types of factories. The anthropogenic input of Cu to soils at local hotspots was closely related to emissions of printing
and dyeing, metallurgical, and chemical factories, whereas a lead oxide factory and a chemical factory resulted in a considerable
increase of Pb in the topsoil of the study area. Approximately 30% of the total land area of the study was at potential risk
from the Cu or Pb diffuse pollution resulting from rapid industrialization of the area over the past 20 years. 相似文献
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The flow characteristics of tidal jets induced by a Tidal-Jet Generator (TJG) are investigated using a finite-difference numerical scheme, named Navier–Stokes (NS)–Marker and Cell (MAC)-TIDE, based on the fully 3D NS equations. The TJG is an enclosed rectangular breakwater, which has vertical opening and a large enclosed volume inside. During both phases of tide, strong and uni-directional jets can be obtained locally from the inlet of the TJG, due to the water level difference between the inner and outer sides of TJG.The computed results are extensively compared with three other independently developed numerical models; 3D-ADI, DVM, and CIP-CSF. These models are based on quasi-3D, 2D depth-averaged, and fully 3D NS equations, respectively. It is seen that the present fully 3D numerical model NS–MAC-TIDE can predict the maximum intensity of inlet velocity with higher accuracy than the other numerical models when compared with the empirical function proposed from the experiments. The numerical simulations based on NS–MAC-TIDE can reproduce successfully the processes of generation, development, and dissipation of tidal jets. The effects of gap opening on the main characteristics of the tidal jet flow are assessed. Through numerical assessment, it is also clearly demonstrated that the residual time of a pollutant distributed around the front of the TJG can be decreased by significant amount due to the locally induced tidal jet. The TJG can thus utilize tidal energy for water purification in local marine environment by providing a flushing mechanism. 相似文献
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