Water-table response to tidal forcing at sloping beaches

The groundwater response to tidal forcing is described by Laplace’s equation for the hydraulic head subject to appropriate boundary conditions. A previous solution to this problem based on long-wave and shallow-aquifer approximations is extended to higher-order and a general solution scheme, automated in Mathematica, is described. The solution can, in principle, be extended to arbitrary order, but is restricted to a detailed study of the properties of the solution when truncated to sixth-order. These results show that the mean water table height increases throughout the aquifer to a steady inland height elevated above mean sea level. The phase shift of the fluctuations and the asymmetry of the pore drainage process are investigated using Fourier analysis.     

Influence of the parameters of sweet-water flow in littoral sea zones on the dimensions of a saline-water tongue

Consideration is given to the model of motion of sweet groundwater in a trapezoidal pressure water-bearing stratum to a sea with saline water. For studying this model, a mixed multiparametric boundary-value problem of the theory of analytical functions is formulated and solved using the P. Ya. Polubarinova-Kochina method. The algorithm of calculation of the intrusion of seawater into the sweet-water layer in the case where its right-hand boundary modeling the littoral zone of the sea floor makes an arbitrary angle with the horizon is developed based on this scheme. The characteristic features of the modeled process and the influence of all determining physical parameters on the character and degree of intrusion are analyzed using the exact analytical dependences obtained and numerical calculations. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 427–433, May–June, 2008.     

A mathematical approach to a forest-impact problem

In this article a mathematical model of forests impact on aquifers is proposed. This phenomenon is the lowering of the groundwater table under areas covered by trees. The model includes a boundary-value problem with contact and free-boundary conditions. A variational formulation of this problem, which is a quasi-variational inequality, is obtained. Its equivalence with the original problem is proved; existence and uniqueness results are obtained. A numerical example of the model is given.     

Underground pollution travel from leach pits of on-site sanitation facilities: a case study

A long-term field study was undertaken under different hydro-geological conditions at some locations of the state of West Bengal (India) to understand the phenomenon of underground pollution movement, and to assess safe horizontal distance of water sources from on-site sanitation leach pits. The study showed that pollution travel from leach pits, both in horizontal and vertical directions, is dependent on soil type, permeability, hydraulic gradient, grain size, and position of groundwater table with respect to the leach pits. A minimum travel of pollutant of 2.055 m was found in clayey silt soil, whereas a maximum travel of 10.20 m was observed in gravel–sand composition of soils in 10-day period. The study also demonstrated that clay envelop around leach pit arrests the movement of pollutant (both chemical and bacteriological) to a considerable extent. In the present study, graphical technique has been suggested for estimating underground travel of bacteriological contamination under given soil composition.     

A time domain approach to SH waves on a piezoelectric layer

The propagation of transient shear horizontal waves in a piezoelectric layer with free boundaries is studied within a time domain approach. The layer is modeled as a dissipative electroelastic continuum via linear constitutive equations accounting for memory effects. A separation of space variables is employed to solve the problem for the Laplace transforms of the fields. The pertinent dispersion equations are derived in different cases where the boundary surfaces of the layer are matched with an external potential or are grounded. It is shown that transient wave solutions exist which are compatible with given time-dependent data at the surfaces. The wave amplitude decays along the layer according to the dissipative model and the potential field outside the layer, in the matched case, turns out to vanish as the reciprocal of the distance from the boundaries. Illustrative examples are given for a square pulse applied to the layer's surfaces.     

Deformation due to mechanical and thermal sources in generalised orthorhombic thermoelastic material

A dynamical two-dimensional problem of thermoelasticity has been considered to investigate the disturbance due to mechanical (horizontal or vertical) and thermal source in a homogeneous, thermally conducting orthorhombic material. Laplace-Fourier transforms are applied to basic equations to form a vector matrix differential equation, which is then solved by eigenvalue approach. The displacements, stresses and temperature distribution so obtained in the physical domain are computed numerically and illustrated graphically. The numerical results of these quantities for zinc crystal-like material are illustrated to compare the results for different theories of generalised thermoelasticity for an insulated boundary and a temperature gradient boundary.     

Two-dimensional DNAPL migration affected by groundwater flow in unconfined aquifer

The dense non-aqueous phase liquid (DNAPL) migration process was experimentally investigated in a laboratory-scale tank (150 cm width, 82.5 cm height, and 15 cm depth) to assess a site characterization on DNAPL contamination below a groundwater table. The heterogeneous ground of the tank model consisted of Toyoura sand (hydraulic conductivity, k = 1.5 x 10(-2) cm/s for void ratio, e = 0.62) and silica #7 sand (k = 2.3 x 10(-3) cm/s for e = 0.72). A series of experiments was carried out with or without lateral groundwater flow. Hydrofluoroether was used as a representative DNAPL. The main results obtained in this study are as follows: (1) the DNAPL plume does not invade into the less permeable soil layer with higher displacement pressure head; (2) the DNAPL plume migrates faster with lateral groundwater flow than without it; (3) lateral groundwater flow does not affect lateral DNAPL migration; rather, it promotes downward migration; and (4) pore DNAPL pressure without groundwater flow is higher than that with it. The above experimental results were compared with numerical analysis. The fundamental behaviors of DNAPL source migration observed experimentally are expected to be useful for assessing the characteristics of two-dimensional DNAPL migration in an aquifer.     

近海面水层中声传播损失估计和分析

近海面水层通常存在声速梯度变化,并随着季节的更替而改变。根据南海典型中等深度海在春季、夏季、秋季和冬季的声速剖面,分析近海面水层中12 km水平距离内声传播损失的空间分布和频率变化规律。结果表明:春、夏两季由于负梯度声影区现象,声传播损失约在1 km的距离超过80 d B;秋、冬两季的典型特征是存在表面声道现象,当声源在近海面混合层内部时,混合层中声传播损失在截止频率以上小于球面扩展损失,而当声源深度大于混合层深度时,表面声道现象不明显。     

Riverbank filtration for sustainable water supply: application to a large-scale facility on the Nile River

Riverbank filtration (RBF) is an efficient and low-cost natural alternative technology for water supply application in which surface water contaminants are removed or degraded as the infiltrating water moves from the river/lake to the pumping wells. The removal or degradation of contaminants is a combination of physicochemical and biological processes. For more than 100 years, RBF has been used in Europe for public and industrial water supply along Rhine, Elbe, and Danube rivers. This paper presents an investigation of a full-scale RBF plant located in Upper Egypt as section of Nile valley to produce drinking water. The studied plant is constructed in 2004 to supply potable water for Sidfa city (30,000 residents), Assiut Governorate. It consists of 6 vertical wells, each about 60 m deep, with distance about 30 m from the west bank of Nile. Water samples from Nile as induced surface water, from background groundwater, and from production wellfield were collected and analyzed at three discrete events. Quality measurements of physical, chemical, and microbiological characteristics were obtained. Comparison of produced water with surface and background natural groundwater for the investigated plant has proven the effectiveness of RBF technique for potable water supply in Upper Egypt. Physicochemical and microbiological characteristics of the produced water are better than the allowable standards for drinking purposes. The results prove the implementation of RBF treatment method for water supply in Nile valley.     

Natural convection heat transfer of cold water in an eccentric horizontal cylindrical annulus — a numerical study

A numerical study of the natural convection heat transfer of cold water, having the density inversion between two isothermal eccentric horizontal cylinders is studied. A general code is developed for the body fitted coordinate system. This procedure transforms an arbitrarily shaped physical domain into a rectangular (square) domain. The governing equations in this computational domain are solved by the upwind finite difference scheme. The numerical solutions are obtained for a Rayleigh number (Ra) ranging between a Prandtl number (Pr) 12.0 and inversion parameter (γ) 0,−1 and −2. The affect of the radius ratio (R) on the flow patterns and heat transfer coefficients is studied by taking the Radius ratio as 1.5 and 2. The eccentricity affect is studied by moving the center of the inner cylinder horizontally and vertically (both positive and negative directions) with respect to the center of the outer cylinder. For the cases considered in the present study, it is again for the minimum heat transfer is observed like in the case of concentric annulus.