冲刷漏斗纵剖面形态数值模拟技术研究   总被引：1，自引：0，他引：1       下载免费PDF全文

冯小香  张小峰  韦直林  李建兵 《水科学进展》2008,19(1):19-26

提出σ坐标系垂向分层的优化方法,较好地解决了传统σ坐标变换用于底孔泄流数值模拟时存在网格边界变化的问题;采用一维水流模型为立面二维模型提供自由水面边界,即"动刚盖法"确定自由表面;根据坝前趋孔水流的流动特性和水下纵坡稳定性受力分析,分别导出σ坐标系下床面泥沙边界条件和底孔泄流初期河床滑塌的判别式。在此基础上建立底孔泄流条件下立面二维水流泥沙数学模型,并将之应用于有刚性护坦条件下冲刷漏斗形成的数值模拟。模拟结果表明,漏斗冲刷平段长度、漏斗纵坡等数值试验结果与水槽试验基本一致,验证了模型的合理性和可靠性。  相似文献   

Models for recession flows in the upper Blue Nile River     

A. Mishra  T. Hata  A. W. Abdelhadi 《水文研究》2004,18(15):2773-2786

Stream‐flow recessions are commonly characterized by the exponential equation or in the alternative power form equation of a single linear reservoir. The most common measure of recession is the recession constant K, which relates to the power function form of the recession equation for a linear reservoir. However, in reality it can be seen that the groundwater dynamics of even the simplest of aquifers may behave in a non‐linear fashion. In this study three different storage–outflow algorithms; single linear, non‐linear and multiple linear reservoir were considered to model the stream‐flow recession of the upper Blue Nile. The recession parameters for the linear and non‐linear models were derived by the use of least‐squares regression procedures. Whereas, for the multiple linear reservoir model, a second‐order autoregressive AR (2) model was applied first in order to determine the parameters by the least‐squares method. The modelling of the upper Blue Nile recession flow performed shortly after the wet season, when interflow and bank storage may be contributing considerably to the river flow, showed that the non‐linear reservoir model simulates well with the observed counterparts. The variation related to preceding flow on a recession parameter of the non‐linear reservoir remains significant, which was obtained by stratification of the recession curves. Although a similar stratification did not show any systematic variation on the recession parameters for the linear and multiple linear reservoir models. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

突水系数法在大淑村煤矿西翼6号煤安全开采中的应用     

王晓军 《中国煤炭地质》2015,(1):40-43

大淑村矿从勘探到生产阶段,对奥陶系石灰岩含水层的专门水文地质勘探程度较低,其含水层富水性及其变化规律,地下水补给、径流条件及水文地质单元划分尚未完全明确,对矿井后续生产拟开采的6号煤层,开采中受到水压高达4~10MPa的下伏巨厚奥陶系石灰岩岩溶裂隙承压水的潜在威胁,底板水害影响程度无法进行较为准确的评价。通过西翼奥灰放水试验,利用获得的主要水文地质参数,计算出6号煤层底板突水系数。经用突水系数法预算,开采西翼6号煤层时,奥陶系中统峰峰组石灰岩含水层水头高度需下降192.17m,其预计涌水量为924.43m3/h,才能满足煤层底板突水系数小于0.06MPa/m的要求,开采6号煤层才是安全的。  相似文献   

A simple concept for calibrating runoff thresholds in quasi‐distributed variable source area watershed models     

Zachary M. Easton  M. Todd Walter  Daniel R. Fuka  Eric D. White  Tammo S. Steenhuis 《水文研究》2011,25(20):3131-3143

Most semi‐distributed watershed water quality models divide the watershed into hydrologic response units (HRU) with no flow among them. This is problematic when watersheds are delineated to include variable source areas (VSAs) because it is the lateral flows from upslope areas to downslope areas that generate VSAs. Although hydrologic modellers have often successfully calibrated these types of models, there can still be considerable uncertainty in model results. In this paper, a topographic‐index‐based method is described and tested to distribute effective soil water holding capacity among HRUs, which can be subsequently adjusted using the watershed baseflow coefficient. The method is tested using a version of the Soil and Water Assessment Tool (SWAT) model that simulates VSA runoff and is applied to two watersheds: a New York State (NYS) watershed, and one in the head waters of the Blue Nile Basin (BNB) in Ethiopia. Daily streamflow predicted using effective soil water storage capacities based only on the topographic index were reassuringly accurate in both the NYS watershed (daily Nash Sutcliffe (E) = 0·73) and in the BNB (E = 0·70). Using the baseflow coefficient to adjust the effective soil water storage capacity only slightly improved streamflow predictions in NYS (E = 0·75) but substantially improved the BNB predictions (E = 0·80). By comparison, the standard SWAT model, which uses the traditional look‐up tables to determine a runoff curve number, performed considerably less accurately in un‐calibrated form (E = 0·51 for NYS and E = 0·45 for BNB), but improved substantially when explicitly calibrated to streamflow measurements (E = 0·76 for NYS and E = 0·67 for the BNB). The calibration method presented here provides a parsimonious, systematic approach to using established models in VSA watersheds that reduces the ambiguity inherent in model calibration. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

人口流出地区城镇化路径机制再认识——以四川省县域单元为例   总被引：1，自引：1，他引：1  

肖磊  潘劼 《地理科学进展》2020,39(3):402-409

论文以四川省县域单元为研究对象,探讨了人口流出地区城镇化发展的特征与机制。研究发现,不同于沿海地区,四川省县域城镇化以生活为主导,农民进城的目标以生活与教育为主,而非进城务工。进城人群的主体是劳动力大量流失后剩下的留守人群,进城生活的经济来源相当程度上依赖外出劳动力打工收入的返还。在产业支撑城镇化能力较弱的同时,形成了异地工业化带动本地城镇化的特殊模式。在特殊的人口进城机制影响下,人口流出地区往往呈现特殊的城镇化表现,如人口流出越多,城镇化速度越快,县城可以脱离制造业而繁荣发展,县域城镇人口增速远超过地级市等。基于新的认识,研究对城镇化机制相关认识进行了探讨,并就此类地区城镇化发展的长期趋势、潜在问题进行了展望。  相似文献   

Ferromanganese crusts as indicators for paleoceanographic events in the NE Atlantic   总被引：4，自引：0，他引：4  

A. Koschinsky  P. Halbach  J. R. Hein  A. Mangini 《International Journal of Earth Sciences》1996,85(3):567-576

Hydrogenetic ferromanganese crusts reflect the chemical conditions of the sewater from which they formed. Fine-scale geochemical analysis of crust layers in combination with age determinations can therefore be used to investigate paleoceanographic changes which are recorded in geochemical gradients in the crusts. At Tropic seamount (off northwest Africa), uniform crust growth influenced by terrigenous input from the African continent occurred during approximately the past 12 Ma. Phosphatization of these crusts is minor. In contrast, crusts from Lion seamount, located between Madeira and the Portuguese coast, display a much more variable growth history. A pronounced increase in Ni, Cu, and Zn is observed in some intervals of the crusts, which probably reflects increased surface productivity. A thick older phosphatized generation occurs in many samples. Hydrographic profiles indicate that Mediterranean outflow water (MOW) may play an important role in the composition of these crusts.¹⁰Be dating of one sample confirms that the interruption of the MOW during the Messinian salinity crisis (6.2–5 Ma ago) resulted in changes in element composition. Sr-isotope dating of the apatite phase of the old crust generation has been carried out to obtain a minimum age for the older generation of Atlantic crusts and to determine whether crust phosphatization in the Atlantic can be related to phosphatization episodes recorded in Pacific crusts. The preliminary data show that the old phosphatized crust generation might be as old as approximately 30–40 Ma.  相似文献   

激电法预报地下涌水量的回归分析方法研究   总被引：3，自引：1，他引：3  

杨进  曲维娟 《物探与化探》1997,21(5):371-376

本文介绍经验回归函数的建立,回归系数的显著性检验及回归预测方法,并以山西五台山北麓峪河洪积扇找水实测资料为列,分析了激电参数与富水性之间存在相关性。  相似文献   

A model approach for in- and outflow calculation of upper lake constance: —An investigation of a 60 year time span and observations about the flood of 1999     

Gustav Wagner  Heinz Gerd Schrder  Joachim Gurtz 《Limnologica》2002,32(1)

The revised empirical model for in- and outflow calculation of Upper Lake Constance has provided satisfying results supported by measured values. The given model was implemented to simulate total water inputs of the lake during the period from 1941 to 2000 with emphasis on the flood conditions of 1999. Analysis of annual water input development reveals a tendency toward slight increases until the 1960s. Thereafter, a reduction in inputs can be noted. This trend probably continues to hold true to present. Weather conditions of given individual years have caused distinct fluctuations to the water budget.Unusual meteorological conditions led to extreme flooding in early May of 1999. Daily water inputs of up to 200 mio m³ generated the highest water levels ever observed for this time of the year. Continual extraordinarily high water inputs occurring from February until July and then again from September until the end of 1999 resulted in the second largest annual total water input recorded since 1941.  相似文献   

一次后向传播对流风暴特征及传播机制     

武冰路  尹泽疆  王萌  秦睿  程月星 《气象科技》2020,48(6):836-845

利用常规观测资料、FY 4A气象卫星红外云图以及多普勒天气雷达资料，分析了2019年5月17日夜间发生在京津冀中部伴有强冰雹、短时强降水和短时大风的强对流天气过程。利用VDRAS资料与国家自动站资料进一步揭示对流风暴形成的环境条件以及后向传播的机制。结果表明：在有利于强对流发生发展的大尺度环流背景场下，京津冀中部的对流系统迅速发展。前期京津一带的强对流天气形成较强的东北风冷池出流，与渤海湾的东南气流交汇，在廊坊北京交界一带形成了向南移动的地面辐合线,并触发了对流。由于新生风暴单体与成熟风暴之间的正反馈作用，使得在廊坊北部形成东西向带状风暴系统，造成对流风暴不断向西传播。向西传播的风暴与西北东南向的平流共同作用，最终导致风暴运动方向为西南方向，成为典型的后向传播风暴。  相似文献   

Factors influencing variability of mercury input to the southern Baltic Sea     

《Marine pollution bulletin》2014,87(1-2):283-290

The southern Baltic countries have been identified as significant sources of Hg into the sea. Are anthropogenic activities the sole source? How do meteorological parameters influence the deposition? Studies on input of Hg to the Baltic were conducted in 2008–2012 in the Polish coastal stations. The riverine load was found to depend directly or indirectly on the amount of precipitation and catchment type. Input of atmospheric Hg increased along with the number of precipitation episodes from remote maritime air masses, as well as with the number of days when continental air masses from regional (when domestic heating prevailed) and remote sources moved over the Baltic, during the heating season. During the non-heating season metal input was found to be proportional to episodes of rain from continental regional air masses and to the number of days under influence of continental and maritime air masses from regional sources.  相似文献