Experimental Study of Sand Bed Configurations in Front of a Vertical Wall Under Wave Action     

JAN Chyan-Deng 《中国海洋工程》1998,(4)

—When a 2-D progressive wave train normally or obliquely approaches a vertical wall and thenis normally or obliquely reflected from it,the combination of the approaching and reflected waves may re-sult in a standing wave or a short-crested wave in front of the wall.This paper presents the experimentalobservations of sand bed configurations under the action of these water waves in front of the wall.The ge-ometry of sand ripples under these water waves in front of the vertical wall is presented as a function offlow parameters,such as the water particle semi-excursion and the mobility number.  相似文献   

Characterizing random wave surface elevation data     

J.M Niedzwecki  J.W van de Lindt  E.W Sandt 《Ocean Engineering》1998,26(5):401-430

The definition and subsequent use of dimensional and dimensionless parameters to characterize various nonlinear aspects of ocean surface waves has again become a matter of great interest to the offshore community. The desire to ascertain whether laboratory simulations are adequately representing the surface waves found in the oceans and the concern over the mechanisms behind platform response phenomena, like ringing, has driven this resurgence of interest. This paper presents a depth independent characterization of single design waves, from which improved estimates of localized wave crest front and back slopes follow that are consistent with discrete time series analysis. Characterization of the nature of the entire wave data recorded requires a combination of spectral parameters and probabilistic models in addition to those used in the design wave characterization. A new expression for the direct evaluation of the kurtosis from knowledge of the spectral bandwidth, the relationship between some of the common spectral parameters, and some modified spectral parameters are presented and discussed. Three illustrative examples are presented. The first example provides a detailed examination of wave data measured from a series of random amplitude and random phase tests in a large model basin. The second presents estimates of the various parameters for the Pierson-Moskowitz and Wallops wave spectrum models. The third example investigates the use of the spectral peakedness ratio for comparing data with selected wave spectrum models. The examples illustrate how the formulae can provide a comprehensive local and global parametric characterization of surface wave elevation data.  相似文献   

均匀介质n维随机波动的空间结构   总被引：1，自引：0，他引：1  

吴克俭  孙孚  宋金宝 《海洋学报》1998,20(2):14-19

研究了均匀介质中n维随机波动的空间结构.导出了外观振幅、波数和相位的联合分布,据此分布,所有与空间有关的波要素的统计分布皆可导出.定义了外观波数谱并得到了其平衡区指数的上界为一(n+2).二维时,海浪外观波数谱平衡区指数的上界与Phillips通过动力学分析导出的Fourier波数谱平衡区指数完全一样.  相似文献   

单视数SAR图像Speckle滤波方法的研究   总被引：2，自引：0，他引：2  

徐新  廖明生  朱攀  卜方玲 《武汉大学学报(信息科学版)》1999,24(4):51

在分析单机数SAR影像的Speckle局部统计特性和现有的空间滤波算法的基础上,提出了一种新的Speckle滤波方法,该方法采用特殊的滤波窗口邻域划分方法,根据窗口相对标准差自适应地调整窗口尺寸和窗口内的滤波区域。该方法被用于多幅单视数ERS-1/2SAR图像去Speckle处理,并与以往的典型算法进行了比较,取得了较好的实验结果。  相似文献   

灌浆强度数值数学模型初步研究          下载免费PDF全文

彭环云  黄树华  贺茉莉 《探矿工程》1999,(6):1-3

通过对灌浆试验情况的分析,得出了影响灌浆强度数值的各种因素,并在此基础上,经过多元线性回归,推出了该值与影响因素之间的经验回归公式,供进一步研究和工程实践参考。  相似文献   

相关观测情况的可靠性研究   总被引：12，自引：3，他引：9  

欧吉坤 《测绘学报》1999,28(3):189-194

可靠性是测量网优化设计和数据质量控制要考虑的重要因素之一。在独立观测情况,测量网的可靠性可用多余度（或称多余观测分量）来表示,多余度越小,该余度越小,该观测位置的可靠性越差,但在相关观测情况,多余度的值域超出（０,１）区间,已不能可靠性特征。本文建议采用一种新的可靠性度量指标：ｒｉ＝（ＰＲ）ｉｉ／Ｐｉｉ,其中Ｐ是观测权阵,Ｒ是平差因子阵。ｒｉ的值域在一种新的可靠性度量指标;ｒｉ＝（ＰＲ）ｉｉ／ｐｉ  相似文献   

MAPGIS在内蒙古1: 50万数字地质图中的应用     

孙政平  张梅 《内蒙古地质》1999,(3)

ＭＡＰＧＩＳ是具有国际先进水平的完整地理信息系统。利用这套系统完成的内蒙古１∶５０ 万数字地质图是新一代的地质图件,具有传统地质图件无法比拟的先进功能。它可随时进行地质、地理内容的更新与修改;可按用户要求做图面分幅与投影转换;可进行各种地质、地理信息的分层检索与输出;对图中重要的地质内容,如地层、岩体、区域性大断裂、同位素年龄等建立了数据库,使其具有可视化功能;可与其他计算机图件进行迭置分析  相似文献   

两相饱和介质中的集中力点源位移场解与应用   总被引：20，自引：4，他引：16       下载免费PDF全文

丁伯阳  樊良本  吴建华 《地球物理学报》1999,42(6):800-808

通过两相饱和介质Ｂｉｏｔ方程变换,利用势场分解较好地解决了饱和两相介质中Ｐ１和Ｐ２波的耦合问题．再由Ｐｏｉｓｓｏｎ方程和Ｈｅｌｍｈｏｔｚ方程的特性,求解得到两相饱和介质在集中力点源作用下的位移场Ｇｒｅｅｎ函数,进而通过阶跃函数和Ｆｏｕｒｉｅｒ逆变换,求得两相介质在集中力．作用下的波场．由上述结果,根据扩容进水模型,合理地解释了孕震前各主要阶段在地震记录中垂直向振幅与振幅比统计值的变化．最后结合工作实例,利用两相介质波场理论求得由一般弹性介质理论不易求得的骨架固体力学参数．  相似文献   

华北北部克拉通地壳岩石的波速特征与地壳物质组成   总被引：8，自引：0，他引：8       下载免费PDF全文

张友南  孙君秀 《地震地质》1999,21(2):52-155

在高温高压条件下对华北北部太古宙变质岩做了波速（ＶＰ）测定,经拟合公式处理后划分出代表岩石酸性程度的波速级数,结合地质、地震测深资料,认为这种变质岩现时期的上地壳组成为“克拉通岩石组合”,其成分为ＴＴＧ变质岩＋孔兹岩系＋花岗岩＋少量基性变质岩和含石榴石基性岩;下地壳由三部分物质组成：“克拉通岩石组合”物质,太古代后幔源基性和超基性物质,地幔岩浆侵入时“克拉通岩石组合”围岩部分熔融留下的残余基性物质,后两种物质的生成使原“克拉通岩石组合”地壳基性化;中地壳为“克拉通岩石组合”物质＋幔源基性物质  相似文献   

Application of a Boussinesq model for the computation of breaking waves: Part 2: Wave-induced setdown and setup on a submerged coral reef     

C. Skotner  C. J. Apelt 《Ocean Engineering》1999,26(10):37

Based on a set of Boussinesq-type equations with improved linear frequency dispersion characteristics in deeper water, the present paper incorporates the simplified effect of spilling wave breaking into the equations. The analysis is restricted to a single horizontal dimension but the method can be extended to include the second horizontal dimension. Inside the surf zone the vertical variation of the horizontal velocity profile is assumed to be composed of an (initially unknown) organised velocity component below the roller and a surface roller travelling with the wave celerity. This leads to a new set of equations which is capable of simulating the transformation of waves before, during and after wave breaking. The model is calibrated and verified by comparison with several wave flume measurements. The results show that the model produces sound physical results.  相似文献