Investigation of Groundwater Contaminant Discharge into Tidally influenced Surface-water Bodies: Theoretical Analysis

Data from an one-dimensional homogeneous sand column, which is utilized to investigate the effect of tides on the concentration of groundwater contaminants discharging to a surface-water body, demonstrate that the tidal fluctuations in water level elevation create concentration oscillations upgradient of the groundwater discharge locations and there is a resulting decrease in average contaminant concentration at the point of groundwater discharge to a surface-water body. The further upgradient an observation point is located, the smaller the amplitude of the tidally induced concentration oscillations. In addition, an excessive upstream migration of concentration oscillations is observed although there is a net downgradient flow. As the classical groundwater flow and transport model could not reproduce this phenomena, a multi-mobility model is proposed with one highly mobile liquid phase, one less mobile liquid phase and a solid phase. Averaging theory is applied in a first step to develop the macroscopic mass conservation equation from its microscale counterpart and then, in a second step, averaging is again used to reduce dimensionality to one-dimensional governing equations defined along the axis of the column. The simulation confirms the existence of an enhanced tidally induced mixing process and the suitability of our mathematical-physical representation of it.     

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.     

壁面加热湍流相干结构的子波分析实验研究

通过在平板湍流边界层沿流向固壁表面平行放置若干条通电加热的金属细丝,在平板表面形成沿展向周期性分布的温度场,利用该温度场引起的空气热对流,在湍流边界层近壁区域产生一组沿湍流边界层展向周期分布的大尺度流向涡结构,改变了平板湍流边界层中不同尺度结构及其能量分布。采用对壁湍流多尺度结构的子波分析表明,在湍流边界层近壁区域产生规则的流向涡结构将壁湍流各种尺度湍涡结构不规则的脉动有序地组织起来,抑制了壁湍流各种尺度湍涡结构脉动,特别抑制了能量最大尺度湍涡结构的脉动,减小由于湍流脉动引起的在湍流边界层法向和展向的动量和能量损耗,从而减小了湍流的阻力。     

Some Results in the Dynamical Theory of Porous Elastic Bodies

This paper is concerned with the linear dynamic theory of elastic materials with voids. First, a spatial decay estimate of an energetic measure associated with a dynamical process is established. Then, a domain of dependence inequality associated with a boundary-initial-value problem is derived and a domain of influence theorem is established. It is shown that, for a finite time, a solution corresponding to data of bounded support vanishes outside a bounded domain.     

汽车盘式制动器摩擦-振动耦合特性试验研究

本文针对9种具有不同厚薄差和端面跳动量组合的汽车盘式制动器,利用制动器惯性试验台在四种制动压力工况下进行了制动转矩和制动压力的测量,并通过阶次分析与小波分析的方法研究了盘式制动器摩擦特性与制动压力波动之间的耦合关系.研究发现:制动盘的厚薄差和端面跳动会引起法向力的波动,进而引起摩擦系数的波动,并且摩擦系数、制动压力以及制动转矩的波动都与转速存在2阶的阶次关系;摩擦系数静态成分随着相对速度的减小和制动压力的减小而增大;摩擦系数动态部分随制动压力的增大而减小,且主要由制动盘厚薄差引起,端面跳动对其影响不明显.     

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.     

Experimental Investigation into the Vibrations of Shells of Revolution with Added Masses

It is established that the vibrations of some elements excite the whole system consisting of cylindrical and conical shells filled with a liquid and installed on an elastic foundation.     

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.     

Foam Self-Clarification Phenomenon: An Experimental Investigation

This paper is focused on the capabilities of gas–liquid foams to attenuate acoustic waves. It is postulated that the sound attenuation phenomenon in foams is largely governed by the hydrodynamic resistance of the Plateau-Gibbs channels (PGC) to the flow of liquid through them. It is shown that the addition of solid particles to gas–liquid foams has opposite effects depending on the concentration of the added solid particles. As long as the concentration of the added solid particles is smaller than a certain critical value the sound attenuation coefficient increases and as a result in the sound velocity decreases. However, if the concentration of the added solid particles becomes larger than this critical value the attenuation coefficient decreases and the sound velocity increases. When the concentration of the solid particles reaches some critical value, the particles block the Plateau-Gibbs channels and stop the filtration. As a result the attenuation coefficient of the sound wave decreases while the sound velocity, in such three-phase foams, increases. The point at which the sound wave stops attenuating and its velocity starts to increase is known as the point of self-clarification. Based on this postulate and on the results of our preliminary tests the present study provides a plausible explanation to the above-mentioned contradicting effect, and the self- clarification phenomenon.     

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.     

Experimental Investigation of Thermo-Oscillatory Convection

The thermal convection in an air column oscillating with a high frequency in a plane channel whose boundaries are isothermal and have different temperatures is investigated. The experiments were performed for various channel orientations and for a wide range of nondimensional governing parameters, i.e. the gravitational Rayleigh number and the thermo-oscillatory parameter. As follows from the experimental results, for relatively large oscillation amplitudes the latter parameter characterizes the average action of high-frequency oscillations on a non-isothermal incompressible fluid. The regions in which either the thermo-oscillatory or gravitational mechanism of thermal convection predominates are determined. The threshold of excitation of thermo-oscillatory convection under weightlessness conditions is found.     

Bifurcation Analysis and Chaotic Behavior in Boost Converters: Experimental Results

This paper presents an experimental set-up for investigating some dynamic phenomena that can occur in current-programmed boost converters. To this purpose, the paper illustrates bifurcation analyses and possible pathways through which the converter may enter chaos. In particular, based on experimental measurements, it is shown that variations of supply voltage and inductance generate interesting bifurcations and novel routes to chaos.     

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.     

Comparison of the Calculated Results for Hypersonic Flow Past Blunt Bodies with the OREX Flight Test Data

The physico-chemical hypersonic air flow model is verified for the conditions of the experimental vehicle OREX reentry path over the altitude range H = 84 –105 km. The calculations are performed on the basis of both the viscous shock layer equations and the complete system of Navier-Stokes equations. The temperature and chemical component concentration fields calculated within the framework of the two models are in good agreement for H 100 km (Re 300). The numerical results for the heat flux at the stagnation point and the electron concentration agree well with the flight test data over the entire altitude range considered.     

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.     

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.     

激光水推进技术的实验研究

激光水推进技术是一种新概念的推进技术,其原理是以水作为推进工质,通过强激光辐照后水的爆炸、反喷进行驱动,具有很高的冲量耦合系数Cm。本文介绍了以硬铝LY12、黄铜、45号钢和石墨作为基板,通过改变基板表面蓄水槽的深度(0mm,3mm,5mm)进行了较系统的激光水推进实验,研究了不同材质基板和不同水槽深度对推进效能的影响,结果表明,蓄水槽深度为3mm的铝基板的Cm最高,达到了350dyne/w,比直接烧蚀提高了2个量级。通过分析实验数据还初步总结出:推进过程中,基板喷射产物颗粒越细,水推进的Cm就越大;对于金属基板,Cm随板材原子量的增加而减小。     

水-岩作用对岩石抗压强度效应及形貌指标的实验研究

通过测定金川岩样的含水率以及水对岩石抗压强度,采用精度高达0.5μm的Talysurf CLI2000三维表面激光形貌仪,对经过矿井深部地下水作用前后的四种不同岩性的岩石试件进行形貌扫描,结合八个形貌参数作出定量分析对比。实验表明:矿岩遇水软化,岩石抗压强度降低,破坏时不属于脆性破坏,其原因可能就在于由于其中的粘土矿物吸水,当受力压缩时,水受压排出产生压密现象。水-岩作用后岩石表面形貌高度的离散性、粗糙程度变大,高度的分布概率更为集中,由负偏态变为正偏态且高度分布的对称性好于作用前。峰点算术平均曲度Ssc都有规律地降至0.62附近,更具协调性。