Numerical assessment of tsunami attack on a rubble mound breakwater using OpenFOAM®     

《Applied Ocean Research》2018

A numerical assessment study of tsunami attack on the rubble mound breakwater of Haydarpasa Port, located at the southern entrance of the Istanbul Bosphorus Strait in the Sea of Marmara, Turkey, is carried out in this study using a Volume-Averaged Reynolds-Averaged Navier-Stokes solver, IHFOAM, developed in OpenFOAM^® environment. The numerical model is calibrated with and validated against the data from solitary wave and tsunami overflow experiments representing tsunami attack. Furthermore, attack of a potential tsunami near Haydarpasa Port is simulated to investigate effects of a more realistic tsunami that cannot be generated in a wave flume with the present state of the art technology. Discussions on practical engineering applications of this type of numerical modeling studies are given focusing on pressure distributions around the crown-wall of the rubble mound breakwater, and the forces acting on the single stone located behind the crown-wall at the rear side of the breakwater. Numerical modeling of stability/failure mechanism of the overall cross-section is studied throughout the paper.The present study shows that hydrodynamics along the wave flume and over the breakwater can be simulated properly for both solitary wave and tsunami overflow experiments. Stability of the overall cross-section can only be simulated qualitatively for solitary wave cases; on the other hand, the effect of the time elapsed during tsunami overflow cannot be reflected in the simulations using the present numerical tool. However, the stability of the overall cross-section under tsunami overflow is assessed by evaluating forces acting on the rear side armor unit supporting the crown-wall of the rubble mound breakwater as a practical engineering application in the present paper. Furthermore, two non-dimensional parameters are derived to discuss the stability of this armor unit; and thus, the stability condition of the overall cross-section. Approximate threshold values for these non-dimensional parameters are presented comparing experimental and numerical results as a starting point for engineers in practice. Finally, investigations on the solitary wave and tsunami overflow experiments/simulations are extended to the potential tsunami simulation in the scope of both representation of a realistic tsunami in a wave flume and stability of the rubble mound breakwater.  相似文献   

贵州安顺市PM2.5气象输送条件及贡献源空间分布     

曹青  谷晓平  张翅鹏  陈贞宏  吴哲红 《气象与环境学报》2022,38(2):55-61

利用贵州省安顺市2015—2019年大气污染物资料和气象资料,分析安顺市空气质量特征和主要大气污染物特征,通过TrajStat软件中HYSPLIT模型的后向轨迹模式,结合GDAS气象数据、PM_2.5浓度,分析不同季节输送途径及其污染轨迹,采用潜在源贡献作用和浓度权重轨迹分析方法,分析研究期内所有PM_2.5污染日（PM_2.5日浓度高于75 μg·m^-3）输送轨迹垂直与水平方向分布特征。结果表明: PM_2.5是安顺城区主要大气污染物,冬季输送污染轨迹占比较大,输送方向主要为贵州东北方向、偏南方向; 污染日PM_2.5输送路径以贵州东北方向近距离输送为主,该类轨迹基本分布在880—980 hPa高度; 潜在源高值区主要集中在贵阳整个地区、毕节织金县、黔西市、金沙县等,高贡献值区主要集中在安顺紫云县、镇宁县、毕节织金县、大方县等。  相似文献   

Origin,discovery, exploration and development status and prospect of global natural hydrogen under the background of “carbon neutrality”     

《China Geology》2022,5(4):722-733

Global energy structure is experiencing the third transition from fossil energy to non-fossil energy, to solve future energy problems, cope with climate change, and achieve net-zero emissions targets by 2050. Hydrogen is considered to be the most potential clean energy in this century under the background of carbon neutrality. At present, the industrial methods for producing hydrogen are mainly by steam-hydrocarbon (such as coal and natural gas) reforming and by electrolysis of water, while the exploration and development of natural hydrogen had just started. According to this literature review: (1) Natural hydrogen can be divided into three categories, including free hydrogen, hydrogen in inclusions and dissolved hydrogen; (2) natural hydrogen could be mainly from abiotic origins such as by deep-seated hydrogen generation, water-rock reaction or water radiolysis; (3) natural hydrogen is widely distributed and presents great potential, and the potential natural hydrogen sources excluding deep source of hydrogen is about (254±91)×10⁹ m³/a according to a latest estimate; (4) at present, natural hydrogen has been mined in Mali, and the exploration and development of natural hydrogen has also been carried out in Australia, Brazil, the United States and some European countries, to find many favorable areas and test some technical methods for natural hydrogen exploration. Natural hydrogen is expected to be an important part of hydrogen energy production in the future energy pattern. Based on a thorough literature review, this study introduced the origin, classification, and global discovery of natural hydrogen, as well as summarized the current global status and discussed the possibility of natural hydrogen exploration and development, aiming to provide reference for the future natural hydrogen exploration and development.©2022 China Geology Editorial Office.  相似文献   

高低频系统相互作用对Rossby波破碎过程的影响     

张潮  谭言科  李崇银  平已川 《大气科学》2019,43(2):221-232

利用美国国家环境预报中心和能源部（NCEP/DOE）的逐日再分析资料（NCEP-DOE AMIP-Ⅱ）,对2010年12月20日发生在北太平洋一次典型的反气旋式波破碎（AWB）事件进行研究,分析了波破碎过程中等熵位涡场的演变特征,揭示了波破碎过程中高频扰动以及低频信号的逐日演变特征,并对2010年冬季350 K等熵面上逐日高频位涡（PV）扰动和低频变化做经验正交函数（EOF）分析,得到了其主要模态,并从等熵位涡方程出发研究了波破碎过程中位涡高、低频变化的原因。研究表明,波破碎过程中高频低PV空气从北太平洋西部日本附近沿东北方向向对流层上层侵入,而来自阿拉斯加湾附近的高频高PV空气向对流层下层侵入。高频位涡场EOF分解得到的前两个模态共同描述了北太平洋中纬度地区自西向东移动的天气尺度波列;低频位涡场EOF分解的第一模态在北太平洋呈弧形波列结构。天气尺度波在传播过程中受到低频场的平流作用逐渐偏离其传播主要模态的位置,并发生破碎,同时高频流场对高频位涡的平流可以产生低频变化,使得低频变化的空间形态向其冬季主要模态转变。  相似文献   

不同定义的湿位涡分析及在台风中的诊断     

刘赛赛  张立凤  赵艳玲 《大气科学》2019,43(3):565-576

本文对不同定义的湿位涡做了理论分析,并利用1522号台风“彩虹”的数值模拟结果对各种湿位涡进行了诊断。主要结论有:经典湿位涡、广义湿位涡和改进湿位涡的差异主要是由不同定义的位温造成的,相当位温、广义位温和修改位温的构成均是在位温基础上添加一显含水汽的附加量;经典湿位涡、广义湿位涡和改进湿位涡的构成均能分为干、湿分量两部分,其干分量表达式相同,都与Ertel干位涡的定义一样,水物质相变潜热的影响隐含在位温中;不同定义湿位涡的本质差异表现在不同的湿分量上,湿分量的表达式中显含了水物质的作用。对台风的诊断分析发现,改进湿位涡分布与Ertel干位涡非常相似,呈现中空分布的位涡塔结构,大值区对应眼墙内侧,改进湿位涡湿分量与经典湿位涡的湿分量分布相似,只是湿分量的绝对值更小,这反映了改进湿位涡既能保持干位涡的分布特征,其分布和演变可反映台风的结构和演变,又能合理地体现水汽分布的影响,所以在台风诊断中有更广泛的应用前景。经典湿位涡在低层表现为负值,这与水汽梯度的分布关系很大,但与垂直速度、潜热加热大值区等都没有很好的匹配关系,用其分析台风结构和演变具有一定局限性;广义湿位涡其形式较复杂,仅在近饱和区域才能发挥其诊断优势。  相似文献   

An efficient hybrid integral-equation method for point-absorber wave energy converters with a vertical axis of symmetry     

《Applied Ocean Research》2019

To assist in the prototyping and controller design of point-absorber wave energy converters (WECs), an easy-to-implement hybrid integral-equation method is presented for computing the frequency-domain hydrodynamic properties of bodies with a vertical axis of symmetry in waves. The current hybrid method decomposes the flow domain into two parts: an inner domain containing the body and an outer domain extending to infinity. The solution in the inner domain is computed using the boundary-element method, and the outer-domain solution is expressed using eigenfunctions. Proper matching at the domain boundary is achieved by enforcing continuity of velocity potential and its normal derivative. Body symmetry allows efficient computation using ring sources in the inner domain. The current method is successfully applied to three different body geometries including a vertical truncated floating cylinder, the McIver toroid, and the coaxial-cylinder WEC being developed in the authors’ laboratory. In particular, the current results indicate that, by replacing the flat bottom of the coaxial-cylinder WEC with the Berkeley-Wedge (BW) shape, viscous effect can be significantly reduced with only minor negative impact on wave-exciting force, thus increasing WEC efficiency. Finally, by comparing to experimental measurements, the current method is demonstrated to accurately predict the heave added mass and wave-exciting force on the coaxial-cylinder WEC with BW geometry. If a viscous damping correction factor is used, the heave motion amplitude can also be accurately computed.  相似文献   

广西合浦、南宁、宁明、百色盆地烃源岩有机地球化学特征与勘探潜力分析   总被引：2，自引：1，他引：1  

邵昌民  赵斌 《海相油气地质》2011,16(1):33-44

广西合浦、南宁、宁明等第三系盆地的主要烃源岩层与百色盆地一样,均是中始新统深湖-半深湖相暗色泥质岩层,特点是分布面积广,厚度大,有机质丰度高.有机碳含量多数大于2.0%,达到"好"到"最好"的评价标准.有机质成熟度多数处于低熟阶段,部分在成熟阶段.干酪根类型主要为Ⅱ1型.综合分析认为:合浦、南宁、宁明三个盆地都具有优质...  相似文献   

Ensemble flood risk assessment in Europe under high end climate scenarios     

《Global Environmental Change》2015

At the current rate of global warming, the target of limiting it within 2 degrees by the end of the century seems more and more unrealistic. Policymakers, businesses and organizations leading international negotiations urge the scientific community to provide realistic and accurate assessments of the possible consequences of so called “high end” climate scenarios.This study illustrates a novel procedure to assess the future flood risk in Europe under high levels of warming. It combines ensemble projections of extreme streamflow for the current century based on EURO-CORDEX RCP 8.5 climate scenarios with recent advances in European flood hazard mapping. Further novelties include a threshold-based evaluation of extreme event magnitude and frequency, an alternative method to removing bias in climate projections, the latest pan-European exposure maps, and an improved flood vulnerability estimation.Estimates of population affected and direct flood damages indicate that by the end of the century the socio-economic impact of river floods in Europe is projected to increase by an average 220% due to climate change only. When coherent socio-economic development pathways are included in the assessment, central estimates of population annually affected by floods range between 500,000 and 640,000 in 2050, and between 540,000 and 950,000 in 2080, as compared to 216,000 in the current climate. A larger range is foreseen in the annual flood damage, currently of 5.3 B€, which is projected to rise at 20–40 B€ in 2050 and 30–100 B€ in 2080, depending on the future economic growth.  相似文献   

Monitoring global land surface drought based on a hybrid evapotranspiration model     

Yunjun Yao  Shunlin Liang  Qiming Qin  Kaicun Wang  Shaohua Zhao 《International Journal of Applied Earth Observation and Geoinformation》2011

The latent heat of evapotranspiration (ET) plays an important role in the assessment of drought severity as one sensitive indicator of land drought status. A simple and accurate method of estimating global ET for the monitoring of global land surface droughts from remote sensing data is essential. The objective of this research is to develop a hybrid ET model by introducing empirical coefficients based on a simple linear two-source land ET model, and to then use this model to calculate the Evaporative Drought Index (EDI) based on the actual estimated ET and the potential ET in order to characterize global surface drought conditions. This is done using the Global Energy and Water Cycle Experiment (GEWEX) Surface Radiation Budget (SRB) products, AVHRR-NDVI products from the Global Inventory Modeling and Mapping Studies (GIMMS) group, and National Centers for Environmental Prediction Reanalysis-2 (NCEP-2) datasets. We randomly divided 22 flux towers into two groups and performed a series of cross-validations using ground measurements collected from the corresponding flux towers. The validation results from the second group of flux towers using the data from the first group for calibration show that the daily bias varies from −6.72 W/m² to 12.95 W/m² and the average monthly bias is −1.73 W/m². Similarly, the validation results of the first group of flux towers using data from second group for calibration show that the daily bias varies from −12.91 W/m² to 10.26 W/m² and the average monthly bias is −3.59 W/m². To evaluate the reliability of the hybrid ET model on a global scale, we compared the estimated ET from the GEWEX, AVHRR-GIMMS-NDVI, and NECP-2 datasets with the latent heat flux from the Global Soil Wetness Project-2 (GSWP-2) datasets. We found both of them to be in good agreement, which further supports the validity of our model's global ET estimation. Significantly, the patterns of monthly EDI anomalies have a good spatial and temporal correlation with the Palmer Drought Severity Index (PDSI) anomalies from January 1984 to December 2002, which indicates that the method can be used to accurately monitor long-term global land surface drought.  相似文献   

广西"6.12"特大暴雨中西南涡与中尺度对流系统发展的相互关系研究   总被引：1，自引：1，他引：0  

陈涛  张芳华  端义宏 《气象学报》2011,69(3):472-485

基于多种观测和数值模式模拟资料,在位涡守恒和反演理论的框架下,对2008年广西"6.12"特大暴雨过程中的西南低涡系统发展过程及其伴随的中尺度对流系统活动特征进行了分析.从天气系统的综合分析看,低涡系统在初始阶段发展相当迅速,东移过程中低空西南急流有明显增强,为中尺度对流系统的活动提供了良好的环境条件.对位涡的诊断分析...  相似文献