基于分层EOF的深海声速剖面时变特征建模          下载免费PDF全文

张林虎  刘杨  刘焱雄  陈冠旭  李梦昊 《海岸工程》2022,41(3):209-222

针对目前局部海域小时间尺度声速场建模方法未顾及不同深度区间内声速变化规律的问题,本文根据实测深海声速剖面的统计特征,提出了声速剖面分层方法,并进一步基于经验正交函数（Empirical Orthogonal Function, EOF）提出了局部小时间尺度的声速剖面分层时变模型构建方法。利用南海实测全海深声速剖面数据,分析了分层EOF第一模态系数和等效平均声速的日变化特征,并比较了不同拟合模型的精度。最后,利用试验海区的温度和潮汐数据分析了声速剖面周期变化的影响因素。结果表明： ①声速剖面分层EOF第一模态系数及等效平均声速具有日周期变化特征,上层声速日周期变化特征不明显,中层声速日周期变化特征较明显,下层声速变化较小但仍具有日周期变化特征;②局部海域小时间尺度声速拟合应考虑长期变化项的影响;③试验海区声速剖面EOF第一模态系数变化与温度显著相关,提取的声速剖面时变特征与海区潮汐周期特征基本吻合。  相似文献   

闽江流域水体氨氮降解系数实验模拟研究   总被引：3，自引：0，他引：3  

游雪静  张玉珍  苏玉萍  陈锦  姜炳棋  林燕秋 《福建地理》2014,(1):61-67

本研究采用模拟实验对闽江流域氨氮的降解规律进行研究,降解系数采用稳态一维降解模型进行分析计算,闽江上游流域氨氮的平均降解系数为0.140~0.260 d-1,中下游流域氨氮的平均降解系数为0.099~0.203 d-1。结果表明,闽江上游流域氨氮自净能力比中下游流域的自净能力好,古田溪断面的氨氮平均降解系数低于全国的平均值,说明氨氮自净能力相对较弱,本研究为确定流域水环境容量和纳污能力及制定污染物总量控制提供科学依据。  相似文献   

强迫摇荡运动三维球体水动力系数的CFD计算     

韩翔希  赵成璧  唐友宏  范少涛  林慰  陈晓明 《海洋工程》2014,32(3):96-103

采用计算流体力学(CFD)的雷诺平均法(RANS方法),并考虑了自由表面的影响(采用VOF方法模拟自由表面),来模拟三维球体的单自由度强迫摇荡运动,得到纵荡、升沉及横摇的附加质量与阻尼系数。该数值模拟结果与三维势流理论计算的结果进行比较,趋势基本一致,但CFD方法更能凸显粘性的作用。本文所应用方法能合理给出浮式结构物的水动力系数,更精确描述海洋浮式结构物周围的流场,可应用于船舶与海洋工程浮式结构物的水动力性能研究。  相似文献   

Chalcophile element partitioning between sulfide phases and hydrous mantle melt: Applications to mantle melting and the formation of ore deposits     

《Journal of Asian Earth Sciences》2014

Understanding the geochemical behavior of chalcophile elements in magmatic processes is hindered by the limited partition coefficients between sulfide phases and silicate melt, in particular at conditions relevant to partial melting of the hydrated, metasomatized upper mantle. In this study, the partitioning of elements Co, Ni, Cu, Zn, As, Mo, Ag, and Pb between sulfide liquid, monosulfide solid solution (MSS), and hydrous mantle melt has been investigated at 1200 °C/1.5 GPa and oxygen fugacity ranging from FMQ−2 to FMQ+1 in a piston-cylinder apparatus. The determined partition coefficients between sulfide liquid and hydrous mantle melt are: 750–1500 for Cu; 600–1200 for Ni; 35–42 for Co; 35–53 for Pb; and 1–2 for Zn, As, and Mo. The partition coefficients between MSS and hydrous mantle melt are: 380–500 for Cu; 520–750 for Ni; ∼50 for Co; <0.5 for Zn; 0.3–6 for Pb; 0.1–2 for As; 1–2 for Mo; and >34 for Ag. The variation of the data is primarily due to differences in oxygen fugacity. These partitioning data in conjunction with previous data are applied to partial melting of the upper mantle and the formation of magmatic-hydrothermal Cu–Au deposits and magmatic sulfide deposits.I show that the metasomatized arc mantle may no longer contain sulfide after >10–14% melt extraction but is still capable of producing the Cu concentrations in the primitive arc basalts, and that the comparable Cu concentrations in primitive arc basalts and in MORB do not necessarily imply similar oxidation states in their source regions.Previous models proposed for producing Cu- and/or Au-rich magmas have been reassessed, with the conclusions summarized as follows. (1) Partial melting of the oxidized (fO₂ > FMQ), metasomatized arc mantle with sulfide exhaustion at degrees >10–14% may not generate Cu-rich, primitive arc basalts. (2) Partial melting of sulfide-bearing cumulates in the root of thickened lower continental crust or lithospheric mantle does not typically generate Cu- and/or Au-rich magmas, but they do have equivalent potential as normal arc magmas in forming magmatic-hydrothermal Cu–Au deposits in terms of their Cu–Au contents. (3) It is not clear whether partial melting of subducting metabasalts generates Cu-rich adakitic magmas, however adakitic magmas may extract Cu and Au via interaction with mantle peridotite. Furthermore, partial melting of sulfide-bearing cumulates in the deep oceanic crust may be able to generate Cu- and Au-rich magmas. (4) The stabilization of MSS during partial melting may explain the genetic link between Au-Cu mineralization and the metasomatized lithospheric mantle.The chalcophile element tonnage, ratio, and distribution in magmatic sulfide deposits depend on a series of factors. This study reveals that oxygen fugacity also plays an important role in controlling Cu and Ni tonnage and Cu/Ni ratio in magmatic sulfide deposits. Cobalt, Zn, As, Sn, Sb, Mo, Ag, Pb, and Bi concentrations and their ratios in sulfide, due to their different partitioning behavior between sulfide liquid and MSS, can be useful indices for the distribution of platinum-group elements and Au in magmatic sulfide deposits.  相似文献   

降雨入渗补给地下水数值模拟研究     

何渊 《中国煤炭地质》2014,(7):36-41

针对在地下水资源评价中入渗补给量采用经验估算存在较大误差的问题,以神东矿区为例,在广泛调查矿区包气带岩性结构并结合野外取样、室内参数测定的基础上,采用数值模拟的方法建立包气带水分运移数值模拟模型,定量模拟矿区内不同地段降雨入渗强度,探讨影响降雨入渗强度的主要因素,计算得出研究区降雨入渗系数大致在0.18~0.27,分析认为影响降雨入渗强度的因素有降雨量、潜水埋深、包气带岩性等。其中在研究区广泛分布的风积沙对地下水资源起到了一定的保护作用。  相似文献   

A two‐dimensional model of hydraulic performance of stormwater infiltration systems     

D. Browne  A. Deletic  G. M. Mudd  T. D. Fletcher 《水文研究》2013,27(19):2785-2799

Stormwater infiltration systems are a popular method for urban stormwater control. They are often designed using an assumption of one‐dimensional saturated outflow, although this is not very accurate for many typical designs where two‐dimensional (2D) flows into unsaturated soils occur. Available 2D variably saturated flow models are not commonly used for design because of their complexity and difficulties with the required boundary conditions. A purpose‐built stormwater infiltration system model was thus developed for the simulation of 2D flow from a porous storage. The model combines a soil moisture–based model for unsaturated soils with a ponded storage model and uses a wetting front‐tracking approach for saturated flows. The model represents the main physical processes while minimizing input data requirements. The model was calibrated and validated using data from laboratory 2D stormwater infiltration trench experiments. Calibrations were undertaken using five different combinations of calibration data to examine calibration data requirements. It was found that storage water levels could be satisfactorily predicted using parameters calibrated with either data from laboratory soils tests or observed water level data, whereas the prediction of soil moistures was improved through the addition of observed soil moisture data to the calibration data set. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

On the prediction of the Toce alpine basin floods with distributed hydrologic models     

Nicola Montaldo  Giovanni Ravazzani  Marco Mancini 《水文研究》2007,21(5):608-621

With the objective of improving flood predictions, in recent years sophisticated continuous hydrologic models that include complex land‐surface sub‐models have been developed. This has produced a significant increase in parameterization; consequently, applications of distributed models to ungauged basins lacking specific data from field campaigns may become redundant. The objective of this paper is to produce a parsimonious and robust distributed hydrologic model for flood predictions in Italian alpine basins. Application is made to the Toce basin (area 1534 km²). The Toce basin was a case study of the RAPHAEL European Union research project, during which a comprehensive set of hydrologic, meteorological and physiographic data were collected, including the hydrologic analysis of the 1996–1997 period. Two major floods occurred during this period. We compare the FEST04 event model (which computes rainfall abstraction and antecedent soil moisture conditions through the simple Soil Conservation Service curve number method) and two continuous hydrologic models, SDM and TDM (which differ in soil water balance scheme, and base flow and runoff generation computations). The simple FEST04 event model demonstrated good performance in the prediction of the 1997 flood, but shows limits in the prediction of the long and moderate 1996 flood. More robust predictions are obtained with the parsimonious SDM continuous hydrologic model, which uses a simple one‐layer soil water balance model and an infiltration excess mechanism for runoff generation, and demonstrates good performance in both long‐term runoff modelling and flood predictions. Instead, the use of a more sophisticated continuous hydrologic model, the TDM, that simulates soil moisture dynamics in two layers of soil, and computes runoff and base flow using some TOPMODEL concepts, does not seem to be advantageous for this alpine basin. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Chemical and physical properties affecting strontium distribution coefficients of surficial-sediment samples at the Idaho National Engineering and Environmental Laboratory, Idaho     

M. J. Liszewski  J. J. Rosentreter  K. E. Miller  R. C. Bartholomay 《Environmental Geology》2000,39(3-4):411-426

 The U.S. Geological Survey and Idaho State University, in cooperation with the U.S. Department of Energy, conducted a study to determine strontium distribution coefficients (K_ds) of surficial sediments at the Idaho National Engineering and Environmental Laboratory (INEEL). Batch experiments using synthesized aqueous solutions were used to determine K_ds, which describe the distribution of a solute between the solution and solid phase, of 20 surficial-sediment samples from the INEEL. The K_ds for the 20 surficial-sediment samples ranged from 36 to 275 ml/g. Many properties of both the synthesized aqueous solutions and sediments used in the experiments also were determined. Solution properties determined were initial and equilibrium concentrations of calcium, magnesium, and strontium, pH and specific conductance, and initial concentrations of potassium and sodium. Sediment properties determined were grain-size distribution, bulk mineralogy, whole-rock major-oxide and strontium and barium concentrations, and Brunauer-Emmett-Teller (BET) surface area. Solution and sediment properties were correlated with strontium K_ds of the 20 surficial sediments using Pearson correlation coefficients. Solution properties with the strongest correlations with strontium K_ds were equilibrium pH and equilibrium calcium concentration correlation coefficients, 0.6598 and –0.6518, respectively. Sediment properties with the strongest correlations with strontium K_ds were manganese oxide (MnO), BET surface area, and the >4.75-mm-grain-size fraction correlation coefficients, 0.7054, 0.7022, and –0.6660, respectively. Effects of solution properties on strontium K_ds were interpreted as being due to competition among similarly charged and sized cations in solution for strontium-sorption sites; effects of sediment properties on strontium K_ds were interpreted as being surface-area related. Multivariate analyses of these solution and sediment properties resulted in r² values of 0.8071 when all five properties were used and 0.8043 when three properties, equilibrium pH, MnO, and BET surface area, were used. Received: 30 November 1998 · Accepted: 16 February 1999  相似文献   

双基地激光测风雷达回波信号仿真研究          下载免费PDF全文

李绍辉  孙学金  邵连军  易欣  张传亮 《气象科学》2023,43(4):523-533

本文针对传统的体散射模型并未考虑大气不均匀性对信号传输的影响等问题,通过引入垂直非均匀的大气参数改进了模型,并利用其建立了体目标的双基地激光测风雷达方程,仿真了侧向散射回波信号,并与单基地雷达进行了对比分析。研究表明:水平方向上,双基地激光测风雷达的回波信号分布特征与单基地雷达差异较大,其回波信号等值线在近地面为卵形线,随着探测高度的增加,回波信号等值线逐渐变为以主、被动雷达为焦点的椭圆形,并最终趋近于圆形;垂直方向上,双基地激光测风雷达的回波信号随高度衰减剧烈,近地面的回波能量约为10^-10 J,4 km高度的回波能量约为10^-15J,在中低层大气(0~10 km),回波信号中气溶胶散射占比大,在高层大气(10 km以上),分子散射占比大。  相似文献   

Assessing the impact of the hydraulic properties of a crusted soil on overland flow modelling at the field scale     

Nane Chahinian  Marc Voltz  Roger Moussa  Gwenn Trotoux 《水文研究》2006,20(8):1701-1722

Soil surface crusts are widely reported to favour Hortonian runoff, but are not explicitly represented in most rainfall‐runoff models. The aim of this paper is to assess the impact of soil surface crusts on infiltration and runoff modelling at two spatial scales, i.e. the local scale and the plot scale. At the local scale, two separate single ring infiltration experiments are undertaken. The first is performed on the undisturbed soil, whereas the second is done after removal of the soil surface crust. The HYDRUS 2D two‐dimensional vertical infiltration model is then used in an inverse modelling approach, first to estimate the soil hydraulic properties of the crust and the subsoil, and then the effective hydraulic properties of the soil represented as a single uniform layer. The results show that the crust hydraulic conductivity is 10 times lower than that of the subsoil, thus illustrating the limiting role the crust has on infiltration. Moving up to the plot scale, a rainfall‐runoff model coupling the Richards equation to a transfer function is used to simulate Hortonian overland flow hydrographs. The previously calculated hydraulic properties are used, and a comparison is undertaken between a single‐layer and a double‐layer representation of the crusted soil. The results of the rainfall‐runoff model show that the soil hydraulic properties calculated at the local scale give acceptable results when used to model runoff at the plot scale directly, without any numerical calibration. Also, at the plot scale, no clear improvement of the results can be seen when using a double‐layer representation of the soil in comparison with a single homogeneous layer. This is due to the hydrological characteristics of Hortonian runoff, which is triggered by a rainfall intensity exceeding the saturated hydraulic conductivity of the soil surface. Consequently, the rainfall‐runoff model is more sensitive to rainfall than to the subsoil's hydrodynamic properties. Therefore, the use of a double‐layer soil model to represent runoff on a crusted soil does not seem necessary, as the increase of precision in the soil discretization is not justified by a better performance of the model. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献