两方程湍流模型对内背风波数值模拟的影响          下载免费PDF全文

Xuhui Hu  Xuefeng Zhang  Lei Lin  Lianxin Zhang  Shifan Wang 《大气和海洋科学快报》2021,14(5):30-36

为了深入理解非静力近似下的波-湍相互作用问题,本研究在σ坐标的海洋环境研究和预报模型(MERF)中引入常用的Mellor-Yamada两方程湍混合参数化方案(MY2.5),评估垂向湍混合对小尺度背风波传播过程的影响.瞬时状态场的模拟结果表明,无论是否为非静力近似条件,上述湍参数化方案的引入都会减弱背风波传播的模拟效果.从时间平均场的试验结果来看,垂向湍混合过程会显著减小非静力近似和静力近似之间的差异.此外,能量收支分析的诊断结果表明,MY2.5方案会显著抑制陆坡地形下的背风波传播过程,进而将更多的潮能转化到不可逆的湍混合过程中.  相似文献   

Characterization,modeling, and remediation of karst in a changing environment     

Zexuan Xu  Nicolas Massei  Ingrid Padilla  Andrew Hartmann  Bill Hu 《Environmental Earth Sciences》2018,77(12):476

This introductory editorial paper provides a review and prospective outlook of the achievements and challenges in karst research under a changing environment. A brief discussion of the past and future karst research has been focused on: (1) data and new technologies; (2) modeling of karst flow and reactive transport; (3) responses of karst hydrosystems to climate variability and changes across scales.  相似文献   

Spatial and temporal analyses of air pollutants and meteorological driving forces in Beijing–Tianjin–Hebei region,China     

Zizhan Hu  Xuguang Tang  Chen Zheng  Menglin Guan  Jingwei Shen 《Environmental Earth Sciences》2018,77(14):540

Due to its negative impact on the living environment of human beings, ambient air pollution has become a global challenge to human health. In this study, surface observations of six criteria air pollutants, including PM_2.5, PM₁₀, SO₂, NO₂, CO and O₃, were collected to investigate the spatial and temporal variation in the Beijing–Tianjin–Hebei (BTH) region during 2013–2016 and to explore the relationships between atmospheric pollutants and meteorological variables using quantile regression model (QRM) and multiple linear regression model (MLRM). The results show that BTH region has experienced significant air pollution, and the southern part generally has more severe conditions. The annual average indicates clear decreasing trends of the particulate matters, SO₂ and CO concentrations over the last 4 years and slight increasing trends of NO₂ and O₃ in several cities. The seasonal and monthly characteristics indicate that the concentrations of five species reach their maxima in the winter and their minima in the summer, whereas O₃ has the opposite behaviour. Finally, the pseudo R² values show that the QRMs have the best performance in the winter, followed by spring, fall, and summer. Specifically, all the meteorological factors have significant impacts on air pollution but change with pollutants and seasons. The MLRM results are generally consistent with the QRM results in all seasons, and the inconsistencies are more common in the fall and winter. The results of this research provide foundational knowledge for predicting the response of air quality to climate change in the BTH region.  相似文献   

Extreme deformation characteristics and countermeasures for a tunnel in difficult grounds in southern Shaanxi,China     

Jinxing Lai  Xiuling Wang  Junling Qiu  Jianxun Chen  Zhinan Hu  Hao Wang 《Environmental Earth Sciences》2018,77(19):706

The Qingling–Bashan (QB) mountain region in southern Shaanxi mainly consists of strongly compressive zones from east to west, with tight folds and compressive fractures. There is a wide distribution of soft rocks of various types, such as phyllite and slate, accompanied by complex geological structures. Ironically, tunnel construction in these difficult grounds with complicated geological conditions embraces a high risk of extreme deformation due to various unpredictable reasons, which can frequently cause collapse and result in budget overruns during the construction period. Therefore, it is crucial to conduct effective countermeasures to eliminate or avoid such adverse impacts. This paper provides a case study on the “Yingfeng tunnel” (a tunnel constructed in soft rock consisting of a slate ground) based on a geological survey, indoor experiments and in situ monitoring. A successive rock mass deformation resulted in the tunnel lining seriously intruding into construction clearance and some other sections, even collapsing during the construction. The maximum displacement amount was 62.5 cm, while the maximum deformation speed reached as high as 34.18 mm/day. Additionally, to evaluate the construction impacts of tunnelling-induced geo-hazards, an investigation on extreme deformation was conducted. Considering the time-dependent features of the rock mass deformation, the constraint-convergence method was used to put forward applicable countermeasures in this paper. Finally, from the feedbacks of monitoring results, extreme deformation of the Yingfeng tunnel was effectively controlled.  相似文献   

Development of efficiently coupled thermo-hydro-mechanical model to predict hydraulic fracture morphology in heavy oil reservoirs     

Yongquan Hu  Qiang Wang  Jinzhou Zhao  Ziyi Guo  Yong Zhang  Chun Mao 《Environmental Earth Sciences》2018,77(23):778

The aim of the study involves examining the effect of heavy oil viscosity on fracture geometry in detail by establishing a heavy oil fracturing model and conventional fracturing model based on thermal–hydraulic–mechanical (THM) coupled theory, Walther viscosity model, and K–D–R temperature model. We consider viscosity and density within the heavy oil fracturing model as functions of pressure and temperature while that as constants within the conventional fracturing model. A heavy oil production well is set as an example to analyze the differences between the two models to account for the thermo-poro-elastic effect. The results show that temperature exhibits the most significant influence on the heavy oil viscosity while the influence of pressure is the least. In addition, a cooling area with a width of 0–1 m and varied length is generated near the fracture. The heavy oil viscosity increases sharply in this area, thereby indicating an area of viscosity increment. The heavy oil viscosity increases faster and is closer to wellbore, and a high viscosity increment reduces the mobility of the heavy oil and prevents the fracturing fluid from entering into the reservoir. The special viscosity distribution results in significant differences in pore pressure, oil saturation, and changing trends between these two models. In the heavy oil reservoir fracturing model, the thermal effect completely exceeds the influence of pore elasticity, and the values of the fracture length, width, and static pressure exceed those calculated in the conventional fracturing model. Thus, a comparison of the measured values indicates that the results obtained by considering viscosity as a function of temperature and pressure are more accurate. Therefore, the results of this study are expected to provide good guidelines for the design of heavy oil fracturing.  相似文献   

Characterization of the mechanical properties of a claystone by nano-indentation and homogenization     

Fan Zhang  Hanqun Guo  Dawei Hu  Jian-Fu Shao 《Acta Geotechnica》2018,13(6):1395-1404

Based on the analyses of mineralogical compositions by X-ray diffraction and microstructure by optical microscopy, the Young’ modulus and hardness of a claystone were characterized by the nano-indentation technique and homogenization method. Three distinct microstructural zones are identified in the claystone: clay matrix, a composite matrix of clay and small mineral grains and imbedded quartz grains. The elastic modulus and hardness of different zones were determined by nano-indentation testing. Based on the statistical analysis of nano-indentation results, the spatial mappings and frequency distributions of elastic modulus and hardness of the different zones were obtained. The elastic moduli of main constituent phases of the claystone are then estimated from the nano-indentation tests. These values were further used for the determination of the macroscopic elastic modulus of the claystone using two different homogenization schemes: the dilute scheme and Mori–Tanaka scheme. The predicted values by the homogenization schemes are compared with experimental data obtained from conventional uniaxial compression tests.  相似文献   

世界气象中心(北京)全球预报服务共享平台设计与实现     

胡争光  魏丽  薛峰  周庆亮 《气象科技》2019,47(4):581-591

世界气象中心(北京)建设是中国气象局承担世界气象组织(WMO)的全球数据处理和预报系统(GDPFS)要求的任务,为全球实时气象预报预测业务提供高效丰富的无缝隙天气气候监测、预报、预测分析指导产品及数据产品服务共享,提高区域性国际天气业务会商交流效率,国家气象中心设计并实现了世界气象中心(北京)全球预报服务共享平台,通过分析全球监测、预报预测等业务数据海量、异构、实时性强等特征,采用浏览器/服务器(B/S结构)多层架构和分布式实时处理、任务调度等关键技术实现了全球实况监测、天气模式、气候模式、模式检验数据的高效加工预处理、产品分析制作、产品自动流转、网络服务共享和业务指导等全流程业务功能,并提供了国际天气预报会商等专业化功能。平台自2018年6月6日业务运行以来,已有13个国家和地区注册会商用户,超过15万次全球访问量,为全球专业用户高效提供了全球实时天气监测、预报服务产品业务指导,未来将成为中国气象局对外气象业务指导和气象服务的重要窗口和纽带。  相似文献   

基于双波段图像的玉米长势自动观测技术研究     

胡树贞  张雪芬  何姣. 《气象与环境科学》2019,42(3):34-41

基于双波段图像的玉米长势自动观测方法研究  相似文献   

基于水位波动关联度的济南西部与济南泉群地下水关系研究          下载免费PDF全文

张郑贤  王维平  相华  盖燕如  李凤丽 《水文》2018,38(6):31-36

济南市以"泉城"闻名,近年来城市化进程的加快及地下水开采量的增大,对济南市区泉群喷涌产生了一定程度的影响。对2014～2017年济南西部玉符河下游的杜家庙、南八里、朱家庄等地及市区泉群的趵突泉、黑虎泉的岩溶水位波动规律进行分析,在地下水位波动幅度计算的基础上,利用灰色关联分析方法,从一个新的评价指标"水位波动关联度"的角度探寻济西与济南市区泉群地下水间的联系,为济南市保泉供水提供探索依据。以15d为地下水位均值计算周期,先计算全年的水位波动关联度,再将关联度的计算结果划分为:4～7月、8～11月和12月至次年3月三个时段,分别分析济西各岩溶井水位与泉水位的波动关联度。结果表明,12月至次年3月关联度的计算结果受外界干扰最小,这一时段济西与市区泉群水位波动关联度的均值为0.854,属高关联度,两者地下水位变化规律极其相似,两个地下水系统在统计学上存在着极强的联系。  相似文献   

Cosmogenic 26Al/10Be Burial Dating of the Uplift Rate of Southern Qinling Mountains since the Middle Pleistocene     

LU Yiming  SUN Xuefeng  TU Hu  ZENG Qiongxuan  XU Xinghua 《《地质学报》英文版》2018,92(4):1674-1675

正Objective The Qinling Mountains(QM)in Central China is a natural barrier that corresponds to the boundary between the southern and northern climate and environment(Gong Hujun et al.,2017).Northern QM is relatively steep,and southern QM is in contrast relatively low and gentle.Investigations have shown that the average uplift rate of  相似文献