Investigation of Groundwater Contaminant Discharge into Tidally Influenced Surface-Water Bodies: Experimental Results

An investigation of the effect of tidally influenced water elevations on the concentration of groundwater contaminants discharging to a surface-water body is studied using a one-dimensional homogeneous sand column. A constant water level is imposed upstream, and the downstream water level is controlled by a wave generator that controls the hydraulic head to mimic a 12-h tidal fluctuation. The experimental results demonstrate that the tidal fluctuations in the downstream reservoir result in a decrease in average contaminant concentration at the point of discharge to the tidally influenced surface-water body. The further upstream an observation well is located, the smaller the amplitude of the concentration oscillation. Fourier analysis suggests that the dominant frequency of the pressure at different locations along the length of the column is identically two cycles per day and that the concentration data have a dominant frequency of two cycles per day, but also exhibit harmonics.     

Penetration of Solid Bodies into Concrete

The results of an experimental study of quasistatic and dynamic penetration of solids into sand concrete are presented.Cylindrical bodies with conical tips and a ball were used. The resistance forces are compared for the taper angles of 180?, 90?, 60?, 30?, 9.5? and a ball. The flow character in the quasistatic immersion regime and in dynamic immersion due to inertia is determined.     

Transient Stochastic Analysis of Biodegradable Contaminant Transport: First-Order Decay

A stochastic methodology was used to analyze the field-scale transport of solutes in heterogeneous aquifers with first-order biodegradation. Spectral methods and perturbation techniques were utilized to develop expressions for the field-scale effective parameters in the mean transport model. Expressions were obtained for the longitudinal and transverse macrodispersivity coefficients, and effective velocity and an effective decay parameter for statistically anisotropic, and isotropic, heterogeneous porous medium, respectively. The behavior of these parameters was described as function of time and log K correlation scale. The expressions for asymptotic values of the dispersivity coefficients and effective velocity and decay parameters were also derived for the isotropic case.     

Numerical Investigation of Large Elastoplastic Strains of Three-Dimensional Bodies

A method of stress—strain analysis of elastoplastic bodies with large displacements, rotations, and finite strains is developed. The incremental loading technique is used within the framework of the arbitrary Lagrangian—Eulerian formulation. Constitutive equations are derived which relate the Jaumann derivative of the Cauchy—Euler stress tensor and the strain rate. The spatial discretization is based on the FEM and multilinear three-dimensional isoparametric approximation. An algorithm of stress—strain analysis of elastic, hyperelastic, and perfectly plastic bodies is given. Numerical examples demonstrate the capabilities of the method and its software implementation __________ Translated from Prikladnaya Mekhanika, Vol. 41, No. 6, pp. 36–43, June 2005.     

Investigation of Dynamic Stability Regimes for Axisymmetric Bodies in Supersonic Flow

The problem of supersonic flow past a slender blunt cone with allowance for the reverse boundary-layer effect on the outer flow is solved with the aim of studying the influence of the boundary layer on the damping coefficient of axisymmetric body oscillations. It is assumed that the body executes plane angular, both low-amplitude and low-velocity, oscillations about a center of rotation. A modified version of the method [1] is applied for calculating the time-dependent flow past a body with the viscosity effect taken into account. The high accuracy of the flow parameter determination provided by this technique is confirmed by wind- tunnel experiments on a large-scale cone model (L1 m) at Mach numbers M=4 and 6. The agreement between the calculated and measured data forms the basis for the numerical investigation of the blunt-cone damping coefficient over a wide range of freestream Mach (M=4–20) and Reynolds (Re _L =10⁶–10⁸) numbers. At moderate freestream Mach numbers (M=4 and 6) an appreciable Re _L effect on the damping coefficient was not detected. However, on the hypersonic range this effect manifests itself more strongly, especially when there is gas injection into the boundary layer from the vehicle surface.     

Centrifugal Pendulum Vibration Absorbers: An Experimental and Theoretical Investigation

This paper presents results from tests completed on a rotor system fitted with pendulum-type centrifugal torsional vibration absorbers. A review of the associated theoretical background is also given and the experimental and theoretical results are compared andcontrasted. An overview of the test apparatus is provided and itsunique features are discussed. To the best knowledge of the authors,this is the first time that a systematic study of the dynamic behaviorof torsional vibration absorbers has been undertaken in a controlledenvironment.     

Hydrodynamic Investigation of Certain Groundwater Flows in Coastal Pressurized Aquifers

Mathematical models of certain fresh groundwater flows through a semi-infinite pressurized aquifer toward a salt-water sea (basin, reservoir, etc.) are examined within the framework of two-dimensional steady-state flow theory. In order to study the models, mixed boundary value problems of the theory of analytic functions are formulated and solved using the Polubarinova-Kochina method. Algorithms for calculating the flows are developed on the basis of these models for situations in which groundwater streams arrive at the sea from one side or from below. Both the structure and the characteristic features of the simulated processes and the effect of all the physical characteristics of the models on the nature of the flow are analyzed in detail using the exact analytic dependences obtained and numerical calculations. The calculation results for the two inflow schemes are compared and features of the flows that depend on the initial position of the fluid contact are discussed.     

含刚性体可展开结构的准静态展开分析方法

包含具有一定几何形状刚性连续表面的可展结构可以有效提高展开效率,保证形状精度,具有较高的实用价值.刚性体按需要可为刚性曲板等,一般形状复杂且形式多样,展开分析中描述困难,目前还没有一种通用的处理方法.本文以节点坐标为变量建立一种通用的刚性体运动学方程,将运动学方程引入展开分析之中,利用广义逆矩阵法进行准静态展开过程分析.本文的方法数学描述简洁明快,包含的未知量少,且适用于含任意形状刚性体的可展开结构,数值计算算例验证了方法的有效性.     

Investigation of Physical Processes in the Gas Discharge Region Between Liquid Electrodes

Electrophysical, hydro-gas-dynamic, and thermal characteristics of a discharge arising between liquid electrodes are considered. Spatial visualization of flow patterns in the gas discharge region is performed by using the schlieren technique.     

牙轮钻头变曲率滑动轴承的结构分析与摩擦学性能研究

基于摩擦学原理和接触力学理论,提出了可在牙轮钻头滑动轴承中采用变曲率结构。在不考虑摩擦的情况下,就结构设计和配合关系统等问题进行了分析讨论,划分了准变曲率、吻合变曲率以及间隙变曲等３种结构形式;针对考虑摩擦时的变曲率结构,提出了接触形状优化和预磨合的实施方案。钻头轴承试验结果表明,无论是预设计变曲率还是预磨合变曲率,都能改善轴承摩擦副的摩擦学特性,因而值得进一步研究和推广。     

Experimental‐Theoretical Investigation of the Hydroexplosive Forming of Structural Shells

The paper describes a procedure for numerical modeling of nonlinear axisymmetric processes of hydroexplosive forming in a coupled formulation. Results of numerical solution are compared with experimental data on hydroexplosive loading of circular plates. Good agreement of theoretical and experimental results is obtained.     

Energy Absorption Performance of Bio-inspired Honeycombs:Numerical and Theoretical Analysis

Energy absorption performance has been a long-pursued research topic in design-ing desired materials and structures subject to external dynamic loading.Inspired...     

Investigation of gas blowing into a base cavity

The results of an experimental investigation of various methods of influencing the flow in the near wake by injecting a system of jets and varying the rear-end configuration for a Mach number M=3 are presented. The structure of the base flow and the pressure fluctuations behind an axisymmetric body with a base cavity when circular and annular gas jets are injected is investigated. The results are compared with the data for bodies with a flat base.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 170–172, July–August, 1989.     

不同速度段弹体侵彻岩石靶体的理论分析

随着撞击速度的增加,弹体对岩石类靶体的侵彻机制会发生显著变化,由刚体侵彻逐步转变为半流体侵彻和流体侵彻,3种侵彻机制各自适用的理论模型完全不同。在半流体侵彻阶段,弹体质量损失开始显著增加,造成侵彻效率严重下降,侵彻深度随撞击速度的增加急剧减小。基于提出的弹体质量与速度的理论模型以及弹体刚体段的侵彻阻抗,推导出考虑弹体质量损失的半流体侵彻深度计算公式。对于超高速撞击时的流体动力学侵彻段,通过对流体区和刚性区进行假定,建立动量守恒和伯努利方程,推导给出该阶段弹体的侵彻阻抗,结合弹体质量变化方程推导出侵彻深度的表达式。最后将3个阶段的理论计算结果与花岗岩侵彻试验数据进行了对比验证,侵深和弹体质量变化规律均吻合良好,而且各阶段模型计算结果反映出的侵彻变化规律与实验结果完全一致。     

Application of Fractional Differential Equations for Modeling the Anomalous Diffusion of Contaminant from Fracture into Porous Rock Matrix with Bordering Alteration Zone

Solute diffusion from a fracture into a porous rock with an altered zone bordering the fracture is modeled by a system of two diffusion equations (one for the altered zone and another for the intact porous matrix) with different coefficients of effective diffusivity. Since experimental studies of diffusion into rock samples with altered zones indicate that mathematical models of diffusion based on Fick’s law do not adequately describe the concentration field in a sample, fractional order diffusion equations are chosen in this study for modeling the anomalous mass transport in the rocks. In the case of significantly higher porosity of the altered zone (e.g., this is typical for carbonates) the effective diffusivity here can be much higher than the effective diffusivity of non-altered rocks. By introducing a small parameter that is the ratio of effective diffusivities in the non-altered and altered regions and applying the technique of perturbations, approximate analytical solutions for concentrations in the altered zone bordering the fracture and in the intact surrounding rocks are obtained. Based on these solutions, different regimes of diffusion into the rocks with different physical properties are modeled and analyzed. It is shown that, using experimentally obtained data, the orders of the fractional derivatives in the differential equations can be readily calibrated for the every specific rock.     

Monte Carlo Simulation of Contaminant Transport: I. Long-range Correlations in Fracture Conductivity

We develop a network model of fractures, and use the model to study transport of contaminants by groundwater through natural geological media. The fractures are narrow rectangular channels between large flat parallel plates, which are embedded in the surrounding rock matrix. The fracture-permeabilities and the fracture-widths are obtained from both uniform and fBm distributions. The pressure distribution in the network, and subsequently the velocity of groundwater in each channel, is obtained. The transport problem in an individual fracture is solved in Laplace space using the realized groundwater velocities and network mass conservation. The transform space solutions are then inverted to real time using a fast and efficient inversion algorithm. Monte Carlo simulations are then carried out by repeating the above procedure for a large number of realizations. The main focus of this study is to explore the effects correlated fracture-permeabilities and fracture-widths have on the transport of contaminants. While the primary transport mechanism is convection, we also study such processes as adsorption onto the fracture surface, and radioactive decay. We show how these phenomena, individually and in combination with one another, affect the overall transport process. In addition, we investigate the nature of the mixing zone, and discuss how these results can be helpful in developing remediation techniques for a contaminated site.     

Monte Carlo Simulation of Contaminant Transport: II. Morphological Disorder in Fracture Connectivity

Simulating contaminant transport in fractured geologic media is challenging. Aside from the difficulties encountered in properly modeling the heterogeneities in the hydraulic properties of the fractures and the matrix, it is difficult to quantify and model the disorder in the fracture connectivity. Correct prediction of the spread of contaminants in fractured geologic media is not possible without considering this inherent morphological disorder. Here, we develop a network model of fractures, and use the model to study transport of contaminants. We investigate the influence of morphology on the transport process by introducing disorder in the fracture connectivity through a novel percolation scheme. The network close to the percolation threshold is very complex and allows the contaminant particles to follow many slow paths. This closely captures the physical situation. We show, how the disorder in the network changes the residence time distributions and its various temporal moments. We also show how the residence time distribution and the temporal moments are influenced by the interaction of the disorder with the various transport mechanisms, such as convection, dispersion, adsorption, and first-order decay.     

Experimental and Theoretical Investigation of Surface Electrization in a Combustion Product Flow

The electrization of cooled and non-cooled surfaces in a combustion product flow loaded with charged soot particles is investigated experimentally and theoretically. The charging currents of the inner surface of a cylinder located in a combustion (propane in air) product flow with a relatively high soot content and the charging currents of cooled and non-cooled cylinders located in a combustion product jet with a relatively low soot content are determined. Physico-mathematical models are constructed for the new effects observed experimentally and these models are theoretically and numerically analyzed.