水与流体饱和孔隙介质界面上非镜面反射声场的实验研究   总被引：5，自引：0，他引：5  

诸国桢  朱喜福  郭宏智 《地球物理学报》2001,44(1):83-92

用光学法和发射-接收法研究了水与流体饱和孔隙介质界面上声波的非镜面反射声场．测量了入射角θ_i为16°－80°范围内的反射系数R，记录了θ_i在Rayleigh波临界角θ_c附近±4°范围内两束反射波的反射角、波束位移△、波形和频谱．实验发现：(1)在θ_c附近±4°范围内，观察到θ_i两束反射波A和B，其中波束B沿界面有波束位移△，实验测出△随θ_i增大而减小，并非在θ_i=θ_c时最大．(2)反射角等于θ_i的波束的频谱很接近于入射波的频谱，反射角等于θ_c的波束的频谱相对于入射波有频谱的负偏移．(3)波束A的相位与发射换能器直达波的相位一致，波束B的相位与波束A相反  相似文献   

Spatial averaging of hydraulic conductivity in three-dimensional heterogeneous porous media   总被引：4，自引：0，他引：4  

A. J. Desbarats 《Mathematical Geology》1992,24(3):249-267

Numerical models of groundwater flow require the assignment of hydraulic conductivities to large grid blocks discretizing the flow domain; however, conductivity data is usually available only at the much smaller scale of core samples. This paper describes a geostatistical model for hydraulic conductivity at both the core or point scale and that of grid blocks. Conductivity at the block scale is obtained empirically as a spatial power-average of point scale values. Assuming a multivariate Gaussian model for point log-conductivity, expressions are derived for the ensemble mean and variance of block conductivity. The expression for the ensemble mean of block scale conductivity is found to be similar to an expression for the ensemble effective conductivity of an infinite field derived analytically by earlier authors. Here, block conductivities obtained by power averaging are compared with effective conductivities obtained from a numerical flow model and are found to be in excellent agreement for a suitably chosen averaging exponent. This agreement deteriorates gradually as the log variance of conductivity increases beyond 2. For arbitrary flow field geometry and anisotropic conductivity covariances, the averaging exponent can be calibrated by recourse to numerical flow experiments. For cubic fields and an isotropic spatial covariance, the averaging exponent is found to be 1/3. In this particular case, it was found that flow field discretization at the block scale through local averaging of point conductivities gave similar results to those obtained directly using a point scale discretization of the flow field.  相似文献   

基于BISQ模型双相各向同性介质中地震波数值模拟   总被引：11，自引：2，他引：9  

孟庆生  何樵登  朱建伟  王德利 《吉林大学学报(地球科学版)》2003,33(2):217-221

基于BISQ机制,推导了双相各向同性介质中弹性波数值模拟方程,并借助交错网格有限差分方法进行了波场模拟。证实了三种波(快纵波、慢纵波、横波SV)的存在和波场特征;在合成地震记录中,观测列三种波的反射,由于各种波相互之间的转换,转换波在地震记录中显示也很清楚,这使得波场变得更为复杂化。  相似文献   

A new scheme for numerical modelling of flow and transport processes in 3D fractured porous media     

Andrés Peratta  Viktor Popov 《Advances in water resources》2006

The objective of this work is to develop a new numerical approach for the three-dimensional modelling of flow and transient solute transport in fractured porous media which would provide an accurate and efficient treatment of 3D complex geometries and inhomogeneities. For this reason, and in order to eliminate as much as possible the number of degrees of freedom, the fracture network, fractures and their intersections, are solved with a coupled 2D–1D model while the porous matrix is solved independently with a 3D model. The interaction between both models is accounted for by a coupling iterative technique. In this way it is possible to improve efficiency and reduce CPU usage by avoiding 3D mesh refinements of the fractures. The approach is based on the discrete-fracture model in which the exact geometry and location of each fracture in the network must be provided as an input. The formulation is based on a multidimensional coupling of the boundary element method-multidomain (BEM-MD) scheme for the flow and boundary element dual reciprocity method-multidomain (BE-DRM-MD) scheme for the transport. Accurate results and high efficiency have been obtained and are reported in this paper.  相似文献   

沉水植物黑藻对上覆水中各形态磷浓度的影响   总被引：16，自引：2，他引：16  

王圣瑞  金相灿  赵海超  崔哲  颜昌宙  步青云  楚建周  周小宁 《地球化学》2006,35(2):179-186

室内模拟研究了沉水植物黑藻对上覆水中不同形态磷浓度的影响及其季节性变化,并从沉水植物生长、间隙水和碱性磷酸酶活性(APA)三方面进行了讨论,进一步揭示磷在浅水湖泊水-沉积物界面的交换机理。结果表明,在本研究条件下,上覆水中各形态磷以溶解性总磷(DTP)为主,其他形态磷浓度变异较大,黑藻降低了上覆水中总磷(TP)、溶解性活性磷(SRP)和DTP浓度,也降低了DTP和SRP占总磷的比例,从而使颗粒态总磷(PP)和溶解性有机磷(DOP)占总磷比例升高。黑藻主要通过吸收上覆水中的磷和抑止沉积物、上覆水中APA使上覆水中各形态磷浓度保持较低水平,其中对SRP和DTP浓度的影响更明显。上覆水中各形态磷浓度呈现明显的季节性变化。在7～8月,TP、SRP和DTP浓度呈下降趋势,并在8月达到最低值;9～10月间有所升高,但仍然维持在较低水平,不同采样时间存在波动。  相似文献   

Mantle process beneath Philippine Sea back-arc spreading ridges: A synthesis of peridotite petrology and tectonics   总被引：2，自引：0，他引：2  

Yasuhiko  Ohara 《Island Arc》2006,15(1):119-129

Abstract In order to obtain a general view of the mantle process beneath a back‐arc basin spreading ridge, the diversity of peridotite petrology and tectonic occurrences in two back‐arc basin spreading ridges from the Philippine Sea were examined: the Parece Vela Rift and the Mariana Trough. The Parece Vela Basin spreading ridge (Parece Vela Rift) was a physically fast/intermediate‐spreading ridge, although many tectono‐magmatic features resemble those of slow‐ to ultraslow‐spreading ridges. Two unusual features of the Parece Vela Rift further demonstrate the uniqueness of the ridge: full‐axial development of oceanic core complexes and exposure of mantle peridotite at segment midpoints. The Parece Vela Rift yields a lithological assemblage of residual but still fertile lherzolite/harzburgite, plagioclase‐bearing harzburgite and dunite; similar assemblages are reported from the equatorial Mid‐Atlantic Ridge at the Romanche Fracture Zone and the ultraslow‐spreading ridges from the Indian and Arctic Oceans. The tectono‐magmatic characteristics of the Parece Vela Rift suggest that diffuse porous melt flow and pervasive melt–mantle interaction were the important mantle processes there. Globally, this ‘porous melt flow‐type’ mantle process is likely to occur beneath a segment midpoint of the ridge having a thick lithosphere, typically an ultraslow‐spreading ridge. In contrast, the Mariana Trough is a typical slow‐spreading ridge, exposing mantle peridotite at segment ends. The Mariana Trough yields a lithological assemblage of residual harzburgite and veined harzburgite, a common assemblage among the global abyssal peridotite suite. The tectono‐magmatic characteristics of the Mariana Trough suggest that channeled melt/fluid flow and limited melt–mantle interaction are the important mantle processes there, because of the colder wall‐rock peridotite in the segment end. This ‘channeled melt flow‐type’ mantle process is likely to occur in the shallow lithospheric mantle at the segment ends of any spreading ridges.  相似文献   

多股水平淹没射流水力特性的影响因素研究   总被引：1，自引：0，他引：1       下载免费PDF全文

李艳玲  华国春  张建民  杨永全 《水科学进展》2006,17(6):761-766

采用数值模拟和模型试验相结合的方法,分析了水股分层、坎高、出口体型和跌坎形式等因素对多股水平淹没射流的流态稳定性和水力特性的影响。研究表明,多股多层水平淹没射流较单层多股水平淹没射流流态稳定性好、临底流速低、消能率高,是一种高效的新型消能方式。结合试验结果,提出中孔泄槽以等宽或微收缩为宜、表中孔最优坎高差应大于中孔水流的主流水深、跌坎形式的选择应结合具体工程特点等建议。  相似文献   

深层地热水开采与地面沉降的关系研究   总被引：5，自引：0，他引：5  

林黎  赵苏民  李丹  马风如  李会娟 《水文地质工程地质》2006,33(3):34-37

本文根据天津塘沽区深层地沉观测标观测到的地面沉降数据,分析了深层地下热水开采对地面沉降的影响比例.在分析地热水开采引起地面沉降机理的基础上,通过统计回归方法建立了深层孔隙型地热水开采量与地面沉降量的相关模型;提出了进行地热尾水回灌和建立深层沉降监测网以加强综合研究的防治对策.  相似文献   

多孔介质中水敏性应用的研究综述     

张晓辉  郑西来  林国庆  吴俊文  周骏 《水文地质工程地质》2006,33(4):81-84

水敏现象在石油、岩土和环境工程等领域广泛存在。有效地控制水敏现象的发生，不仅具有科学意义，还有一定的经济价值。本文在广泛查阅国内外研究成果的基础上，总结了水敏性在石油、岩土和环境工程方面应用的研究进展，并在此基础上提出了水敏性研究的发展方向。  相似文献   

利用Landsat 5 TM影像估算沉水植物地上生物量的研究——以江西省鄱阳湖国家自然保护区为例   总被引：5，自引：0，他引：5  

邬国锋  刘耀林  纪伟涛 《武汉大学学报(信息科学版)》2006,31(11):953-957

阐述了利用Landsat 5 TM影像在鄱阳湖国家自然保护区进行沉水植物地上生物量估算的方法和过程。研究结果显示，采用该影像，结合传统的采样策略和估算方法进行生物量的估算，在此研究区域中具有一定的局限性。分析了产生这一问题的原因，并对后续的研究工作提出了具体的建议。  相似文献