Transient‐state groundwater flow in various geometries with wells at arbitrary positions: analytical methods     

M. W. Roth  C. M Wilson  M. Z. Iqbal 《水文研究》2003,17(17):3519-3530

We have developed a method for analytically solving the porous medium flow equation in many different geometries for horizontal (two‐dimensional), homogeneous and isotropic aquifers containing impermeable boundaries and any number of pumping or injection wells located at arbitrary positions within the system. Solutions and results are presented for rectangular and circular aquifers but the method presented here is easily extendible to many geometries. Results are also presented for systems where constant head boundary conditions can be emulated internal to the aquifer boundary. Recommendations for extensions of the present work are briefly discussed. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

土壤渗滤处理技术在海岛生活污水处理中的应用     

焦卫东 《台湾海峡》2005,24(3):304-309

土壤渗滤处理系统设备简单、投资少、操作管理方便、能耗低,净化效果良好,在处理海岛生活污水领域具有广阔的发展前景.根据鼓浪屿目前污水水质、水量的特点,采用土壤渗滤高度水处理技术对污水进行处理,污染物经过土壤的物理、化学和生物作用,出水达到《城市污水再生利用城市杂用水水质》(GB/T18920-2002),具有不产生污泥,运行简单,氮磷去除效率高,无二次污染等特点.  相似文献   

Prediction of local scour around circular piles under waves using a novel artificial intelligence approach     

Iman Ahmadianfar  Xuefeng Chu 《Marine Georesources & Geotechnology》2021,39(1):44-55

Abstract

The scour phenomena around vertical piles in oceans and under waves may influence the structure stability. Therefore, accurately predicting the scour depth is an important task in the design of piles. Empirical approaches often do not provide the required accuracy compared with data mining methods for modeling such complex processes. The main objective of this study is to develop three data-driven methods, locally weighted linear regression (LWLR), support vector machine (SVR), and multivariate linear regression (MLR) to predict the scour depth around vertical piles due to waves in a sand bed. It is the first effort to develop the LWLR to predict scour depth around vertical piles. The models simulate the scour depth mainly based on Shields parameter, pile Reynolds number, grain Reynolds number, Keulegan–Carpenter number, and sediment number. 111 laboratory datasets, derived from several experimental studies, were used for the modeling. The results indicated that the LWLR provided highly accurate predictions of the scour depths around piles (R?=?0.939 and RMSE = 0.075). Overall, this study demonstrated that the LWLR can be used as a valuable tool to predict the wave-induced scour around piles.  相似文献   

A Forced System of Two Cylinders with Various Spacings   总被引：3，自引：0，他引：3  

邹建锋  任安禄邓见 《中国海洋工程》2004,18(3):391-402

The spectrum characteristics and wake structures for a circular cylinder oscillating in a wake are investigated by use of the currently modified virtual boundary method. A forced system of two cylinders with a small spacing ( the downstream one is made to oscillate in the transverse direction) is studied and interesting flow characteristics are observed. A vortex switch and the change of vortex modes (between 2S mode and 2P mode) are observed in the “lock-in“ region. Vortex bands are formed and lost with the increasing excitation frequency. Information concerning saddle points in the flow field is obtained for different excitation frequencies. For a forced system of two cylinders with a large spacing, the upstream cylinder sheds vortexes because there is no downstream cylinder oscillating in the wake. No distinct “lock-in“ response is found for the downstream cylinder.  相似文献   

软粘土中插入式大直径薄壁圆筒结构的一种极限状态分析模型     

王乐芹  周锡礽  张伟 《海洋技术学报》2005,24(1):95-100

根据插入式大直径薄壁圆筒结构的工作特点建立了其合理的破坏机制，以此为基础建立了受横向荷载作用的插入式大直径薄壁圆筒结构的上限法极限分析模型，从中可以得到作用于插入式大直径薄壁圆筒结构上的横向极限荷载近似的上限解；并根据上限法模型计算结果，提出了计算受横向荷载作用的插入式大圆筒结构侧壁极限抗力的简化修正模型，利用此修正模型，基于极限平衡法，可以求解作用于插入式大直径薄壁圆筒结构上的横向极限荷载。  相似文献   

Wave-Current Forces on Vertical Cylinders in Side-by-Side Arrangement for Irregular Waves Combined With Opposing Current     

Li Yucheng Wang Fenglong Professor  Dalian University of Technology  Dalian Senior Engineer  Dalian University of Technology  Dalian 《中国海洋工程》1993,(1)

- The wave-current forces on vertical piles in side-by-side arrangement induced by irregular waves with opposing current are investigated experimentally in this paper. The characteristics in both time and frequency domain of in-line, lift and resultant forces are analyzed. The grouping effect coefficients of inline, lift and resultant forces on piles related to KC number and relative spacing parameters are given. These results are compared with those in the case of irregular waves combined with following currents. It is found that the results in these two cases are quite different. The range of KC number tested is 10- 60, the range of Reynolds number is (0.55-3.43) ×104.  相似文献   

The Nonlinear Wave Force on a Circular Cylinder in Shallow Water     

Qiu Dahong 《中国海洋工程》1992,(2)

Based on the 1st order cnoidal wave theory, the nonlinear wave diffraction around a circular cylinder in shallow water is studied in this paper. The equation of the wave surface around the cylinder is formulated and by using this formula the wave surface elevation on the cylinder surface can be obtained. In this paper, the formula for calculating the cnoidal wave force on a circular cylinder is also derived. For the wave conditions which are often encountered in practical engineering designs, the ratios of the nonlinear wave forces to the linear wave forces are calculated, and the results are plotted in this paper for design purposes. In order to verify the theoretical results, model tests are conducted. After comparing the test results with the theoretical ones, it is concluded that, in shallow water, for the case of T g / d~(1/2) > 8-10 and H / d > 0.3, the cnoidal wave theory should be used to calculate the wave action on a cylindrical pier.  相似文献   

An Approach to Stability Analysis of Embedded Large-Diameter Cylinder Quay   总被引：3，自引：3，他引：3  

WANG  Yuanzhan 《中国海洋工程》2002,16(3):383-393

The large-diameter cylinder structure, which is made of large successive bottomless cylinders placed on foundation bed or partly driven into soil, is a recently developed retaining structure in China. It can be used in port, coastal and off-shore works. The method for stability analysis of the large-diameter cylinder structure, especially for stability analysis of the embedded large-diameter cylinder structure, is an important issue. In this paper, an idea is presented that is, em-bedded large-diameter cylinder quays can be divided into two types, i.e. the gravity wall type and the cylinder pile wall type. A method for stability analysis of the large-diameter cylinder quay of the cylinder pile wall type is developed and a method for stability analysis of the large-diameter cylinder quay of the gravity wall type is also proposed. The effect of sig-nificant parameters on the stability of the large-diameter cylinder quay of the cylinder pile wall type is investigated through numerical calculation.  相似文献   

Measurements of higher harmonic wave forces on a vertical truncated circular cylinder     

S.Y. Boo   《Ocean Engineering》2006,33(2):219-233

Wave forces on a vertical truncated circular cylinder in Stokes waves with the wave slopes ranging from 0.06 to 0.24, are measured in a wave tank. The higher harmonic wave forces are compared with the available values from theories of the FNV (Faltisen–Newman–Vinje) model and Varyani solution. The first harmonic horizontal forces measured are much larger than the theoretical values from the FNV model, while the first harmonic vertical forces are well predicted by the Varyani theory. It was also found that the FNV model significantly overpredicts the second harmonic horizontal forces in high frequency waves, but under predicts the third harmonic forces. The differences between the actual measurement and the theory, in the second and third harmonic horizontal forces, become smaller at low wave frequencies as the wave slope increases. In addition, the transverse instabilities in the incoming waves with high wave slope were observed, which is due to the nonlinear modulation. Measurements were, thus, carried out before the instability occurred.  相似文献   

Wave-Current Forces on Small Square Cylinders (Part I)     

Li Yucheng  He Ming Professor  Dalian University of Technology  Dalian Former master student  Dalian University of Technology  Dalian 《中国海洋工程》1994,(3)

-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coefficient CD and Cu related to KC number and the effect of direction of wave incidence are also given, which can be used in engineering practice.  相似文献