Heat,Water, and Solution Transfer in Unsaturated Porous Media: I -- Theory Development and Transport Coefficient Evaluation

A detailed theory describing the simultaneous transfer of heat, water, and solute in unsaturated porous mediais developed. The theory includes three fully-coupledpartial differential equations. Heat, water, andsolute move in the presence of temperature, T; matricpressure head, _m ; solution osmotic pressure head _o ; and solute concentration C gradients. Thetheory can be applied to describe the mass and energyin radioactive waste repositories, food processing,underground energy storage sites, buried electriccables positions, waste disposal sites, and inagricultural soil. Several transport coefficients forheat, water, and solute are included in the theory. The coefficients are evaluated for a silty clay loamsoil to clarify their dependence on water content (),T, and C. The thermal vapor diffusivity D _Tv first increased as increased to0.22 m³/m³ then decreased with furtherincreases in . D _Tv was 3 orders of magnitudegreater than either isothermal vapor D _mv orosmotic vapor D _ov , diffusivities at of0.20~m³/m³, T of 50°C, and C of 0.001mol/kg. All of the liquid and vapor water transport coefficients increased with increasing T. D _Tv decreased with increasing C to a greater extent thanD _mv and D _ov . The effective thermalconductivity decreased slightly with increasing C. Thesolute diffusion coefficient D _d was 6 to 7orders of magnitude greater than the thermal soluteand salt sieving diffusion coefficients at of0.20~m³/m³, T of 50°C, and C of 0.001 mol/kg.     

A Study of Magma Flows in the Case of Non-Equilibrium Diffusion of Water in the Melt

All volcanic eruptions are accompanied by the degasification of the magma, which results in the growth of gas bubbles in the silicate melt. The number and growth rate of the bubbles determine the character of the eruption. When the free-gas concentration is low, the eruption is weak and takes a short time. At high concentrations, the melt is fragmented and a gas-particle mixture is formed. This results in the catastrophic intensification of the eruption. In this study, for describing the magma flow in a volcano conduit with account for the mass transfer between the bubbles and the melt, we construct models in which the conduit magma flow is considered simultaneously with the dynamics of gas-bubble growth in the melt. The models describe the magma eruptions with equilibrium or weak growth of the bubbles and also with a moderate rate of bubble growth, which is more typical of volcanic systems. Using the models constructed, an intense steady-state eruption and the problem of the evolution of the eruption to the steady-state regime after the rupture of a plug near the top of the conduit are considered. The effect of gas diffusion on the intensity and duration of the eruption is indicated.     

激波管中实验模拟爆炸波对水汽作用的研究

利用激波管中波系间的相互干扰，实验模拟了爆炸波对水汽的作用，并通过光学测试方法，对水汽同质核化、凝结非定常瞬态变化过程进行了测定．结果表明：在爆炸波强度较弱时，水汽不发生凝结；而在一定强度爆炸波后的非定常流场中，水汽会发生同质核化、凝结．这说明较强爆炸波后的绝热冷却过程可以使水汽发生相变     

Analysis and Modeling of the Turbulent Diffusion of Turbulent Kinetic Energy in Natural Convection

Buoyant flows often contain regions with unstable and stable thermal stratification from which counter gradient turbulent fluxes are resulting, e.g. fluxes of heat or of any turbulence quantity. Basing on investigations in meteorology an improvement in the standard gradient-diffusion model for turbulent diffusion of turbulent kinetic energy is discussed. The two closure terms of the turbulent diffusion, the velocity-fluctuation triple correlation and the velocity-pressure fluctuation correlation, are investigated based on Direct Numerical Simulation (DNS) data for an internally heated fluid layer and for Rayleigh–Bénard convection. As a result it is decided to extend the standard gradient-diffusion model for the turbulent energy diffusion by modeling its closure terms separately. Coupling of two models leads to an extended RANS model for the turbulent energy diffusion. The involved closure term, the turbulent diffusion of heat flux, is studied based on its transport equation. This results in a buoyancy-extended version of the Daly and Harlow model. The models for all closure terms and for the turbulent energy diffusion are validated with the help of DNS data for internally heated fluid layers with Prandtl number Pr = 7 and for Rayleigh–Bénard convection with Pr = 0.71. It is found that the buoyancy-extended diffusion model which involves also a transport equation for the variance of the vertical velocity fluctuation gives improved turbulent energy diffusion data for the combined case with local stable and unstable stratification and that it allows for the required counter gradient energy flux.     

Modeling Floodplain Filtration for the Improvement of River Water Quality

A mathematical model was developed to describe a treatment method of floodplain filtration for the improvement of river water quality. The process consists of spraying poor quality river water onto the river floodplains and thus allowing soil filtration to treat water before it gets back again into the main river stream. This technique can be readily employed in Korea because it exploits the characteristics of the climate and rivers in the country, as described in an experimental study of Chung et al. The model was analyzed by numerical methods and validated by comparing the simulated values with experimental data. A scenario analysis of the model was also performed in order to have a better understanding of the floodplain filtration process. Our results show that the model was able to predict the reduction in organic matter and NO₃^– in river water through the floodplain filtration. Furthermore, it was found that only a few decimeters of top soil profile were enough to degrade most of the organic matter under wider operational conditions than those reported in the literature. Also, it was found that significant infiltration of atmospheric oxygen took place near the soil surface. The N₂O emission and the NO₃^– leaching increased with the increase in the influent NO₃^– concentration. However, the N₂O emission due to floodplain filtration was not expected to exceed 0.1 mL/m²-day.     

Almost analytic solutions and their tests of the horizontal diffusion equation for the movement of water in unsaturated soil

Itisalwaysdifficulttofindthesolutionsoftheequationforthemovementofwaterinunsaturatedsoi1.Theprimar}'reasonisthatthehydraulicconductivityK(T)orthediffusivityofsoiIwaterD(o)isfunctionofwaterpotential(W)orwatercontent'(o)'Atpresent,thegeneralwaystofindthesol…     

Migration of salts in the unsaturated zone caused by heating

Heat-transfer phenomena as well as moisture movement in unsaturated soils due to thermal gradients, have been extensively studied during the last four decades. Less attention has been devoted to the transport and redistribution of solutes caused by heating.Solar radiation, radioactive waste repositories, underground energy storage, buried electric cables and steam pipes, disposal of waste heat from power plants are examples of heat sources in the soil.Soil-water properties, such as surface tension, viscosity, density, as well as the equilibrium composition of phases, depend on temperature. Hence, nonuniform heating of a soil partially saturated by saline water has an effect on such processes as water flow under capillary and gravitational forces, evaporation, condensation and diffusion of vapor and transport and precipitation of salts.A mathematical model is presented for the migration of salts in the vadoze zone in the soil under nonisothermal conditions, taking into account the above-mentioned phenomena. The physical assumptions underlying the model are briefly discussed.The study of a particular case shows that under certain conditions, a heat source may attract dissolved salts, and cause their precipitation in the hot area.     

空投鱼雷倾斜姿态落水冲击研究

利用轴长体假设和Ｔａｙｌｏｒ关于圆柱在不同浸深时的附加质量表达式，运用切片理论建立了空投鱼雷在其纵向平面内以倾斜姿态落水时的运动微分方程组，通过实例计算得到了空投鱼雷入水冲击时作用在其上的弯矩和剪力分布的规律，为理论预测空投鱼雷入水冲击时的强度破坏建立了基础。     

Experimental determination of the diffusion coefficients of wood in isothermal conditions

The diffusion coefficients of frake (Terminalia superba) were determined in the radial, tangential, and longitudinal directions at tree different temperatures: 30°C, 35°C an 40°C. The longitudinal diffusion coefficient is larger than the transverse diffusion coefficient. In addition the radial coefficient is larger than the tangential coefficient.     

建筑物内火灾烟羽流和顶蓬射流诱发的空气运动盐水模拟实验研究

盐水在清水中的扩散与火灾烟气在空气中的蔓延相似，因而可用盐水的扩散来模拟火灾烟气的蔓延；同样地，由于盐水的扩散而导致的环境清水的运动也可用来模拟烟气蔓延诱发的空气运动。基于这一原理，本文用实验的方法，研究了建筑物内初起火灾产生的烟羽流和顶蓬射流所诱发的空气运动，并对走廊空气层生长规律和运动特性进行了初步的测量和分析。所得结果基本合理，对建筑物通风排烟及疏散通道设计有帮助，从而为建筑火灾环境空气的运动的实验研究开辟了新的思路，也为火灾区域模拟提供了实验依据     

Modeling the effect of diffusion of the ambient medium on the long-term strength of a hollow cylinder under uniaxial tension

The problem of the long-term strength of an extended thick-walled tube containing a corrosive medium in the internal cavity is solved. The diffusion of this medium into the tube material is analyzed. The diffusion equation is solved approximately by introducing the diffusion front, and the error of the solution is estimated. The dependence of the time of fracture of the tube on the variable tensile stress and the concentration of the medium filling the cavity is obtained. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 4, pp. 88–93, July–August, 2007.     

水深对POM摩擦学性能的影响

本文中以聚甲醛(POM)作为摩擦副材料,与不锈钢(0Cr17Ni12Mo2)配对,研究了POM在0~300 m不同模拟水深(去离子水)中的摩擦磨损性能,并与大气压下干摩擦进行对比,试验目的主要是探寻水深变化引起的水环境压力变化对POM材料摩擦磨损性能的单因素影响.采用白光共焦三维轮廓仪与扫描电子显微镜对试验前后的表面形貌进行测量与分析.结果表明:模拟水深对POM磨损深度及POM/0Cr17Ni12Mo2摩擦副的摩擦系数有较大影响,且有明显规律;在0~300 m模拟水深(去离子水)范围内,随着模拟水深深度的加大,POM的磨损深度和POM/0Cr17Ni12Mo2摩擦副的摩擦系数均有所减少;模拟水深对试样摩擦后的表面粗糙度无明显影响;对主导的磨损机理无明显影响.     

Freezing of Water in a Differentially Heated Cubic Cavity

An experimental and numerical study has been made of transient natural convection of water freezing in a cube-shaped cavity. The effect of the heat transfer through the side walls is studied in two configurations: with the cavity surrounded by air and with the cavity immersed in an external water bath of constant temperature. The experimental data for the velocity and temperature fields are obtained using liquid crystal tracers. The transient development of the ice/water interface is measured. The collected data are used as an experimental benchmark and compared with numerical results obtained from a Finite-difference code with boundary fitted grid generation. The computational model has been adopted to simulate as closely as possible the physical experiment. Hence, fully variable fluid properties are implemented in the code, and, to improve modelling of the thermal boundary conditions, the energy equation is also solved inside the bounding walls. Although the general behaviour of the calculated ice front and its volume matches observations, several details of the flow structure do not. Observed discrepancies between experimental and numerical results indicate the necessity of verifying and improving the usual assumptions for modelling ice formation.     

Unsteady theory of the hydrofoil of finite span

A three-dimensional unsteady flow around the hydrofoil has been dealt with in this paper. Under the assumption of infinitesimal wave and thin hydrofoil, analytic solution of perturbation velocity potential induced by the unsteady flow of a hydrofoil which is simplified as a series of rectangular vortex rings is achieved and then the unsteady forces can be evaluated. The paper had been accepted by the X VI th International Congress of IUTAM, Lyngby, Denmark, Aug. 19–25, 1985.     

水中脉冲放电的压力特性研究

同时利用高速摄影仪和压力传感器研究水中高压脉冲放电的压力特性。实验发现 ,当电容器的电容为 4 .1F ,充电电压为 10kV ,电极间隙为 7mm时 ,水中冲击波的波速为 1 5km s。通过压力传感器测得放电所产生的冲击波和气泡首次回胀时产生的冲击波在离通道 0 3m处的峰值压力分别为 1 5 5MPa和 0 5 5MPa ,模拟计算所得的峰值压力分别为 1 0MPa和 0 3 8MPa ,两者基本相符。另外 ,还根据高速摄影仪所拍摄到的等离子体通道直径的扫描照片 ,计算了在放电 3 0 s后通道内的压力为约 4 9MPa ,通道半径和壁速分别为 4mm和180m s。     

Role of NAPL Thermal Properties in the Effectiveness of Hot Water Flooding

Hot water flooding is a thermal nonaqueous phase liquid (NAPL) recovery technology originally developed in the petroleum industry that has recently been proposed for enhanced recovery of NAPLs in the contaminated subsurface. This technology, however, has received relatively little laboratory or numerical modeling investigation in the contaminant hydrology community. In this study the utility of flooding NAPL contaminated source zones at elevated water temperatures was investigated. Simulations were conducted using 16 different geostatistical representations of an actual field site. Two NAPLs were selected for this study—a light NAPL with hydraulic properties that have moderate temperature dependencies and a dense NAPL with significant viscosity temperature dependency. For these two NAPLs, flooding the source zone with water at elevated temperatures resulted in enhanced NAPL recovery. However, injection of hot water also resulted in accelerated downward movement of coal tar DNAPL due to the reduced viscosity at elevated temperatures. NAPL recovery was also dependent on the source zone architecture with greater NAPL mass recovery when the NAPL was localized in a small volume at high saturations. These results suggest that hot water flooding can significantly speed up the recovery of viscous NAPLs and, as such, is a powerful technique for the remediation of viscous NAPLs.     

Spectral Analysis of the Balance Equation of Ground Water Hydrology

The spectral analysis of the balance equation of ground water flow, associated to an asymptotic expansion of the conductivity (K) and head (h) fields, permits to show that the high wave number components of the source terms, F, and of the conductivity, K, are attenuated when h is computed as solution to the balance equation. This has important consequences on the inverse mapping (h, F) → K: in fact it is not possible to recover in a reliable way the high wave number components of K, because small errors on the corresponding components of h are amplified so that they can hidden the true signal.     

Perfecting a method of micro-analysis of water and acetic acid in a cocoa bean in the course of drying: applying to determine transportation coefficients

This article is about the study of the diffusion of water and acetic acid in a grain of cocoa in course of drying. The authors present a method of microanalysis which enables the analysis of each little slice of the grain : a precise measurement of each slice is realised in view of the analysis from the centre to the surface of the grain with the aid of a cutting apparatus, designed and realised to this effect. At each instant of the drying process, the profiles of water and acetic acid contents are then determined. A one dimensional diffusion model enables a shell by shell evaluation of the diffusion of water and acid in the cocoa grain. The results obtained show an augmentation of transport coefficients in course of drying. We however observe a decrease of the diffusion coefficient of water to the low moisture content : what makes us think of the appearance of crusting phenomenon.     

用Fourier变换莫尔法测量流体自由表面微幅波的振幅

采用一种非接触的光学方法－傅立叶变换莫尔法（Fourier transformmethod），结合数字图像处理技术，对微幅振荡的水表面波的振幅进行测量。它是对全场中每一个像素点进行测量，比较触测量法具有更高的灵敏度。它为微幅水表面波振幅的测量提供了一种手段。通过将计算机生成的周期性光栅图像经投影机直接投影到被测物体的参考平面，经CCD摄像头、图像板捕捉存储形成数字化的光栅图像，利用傅立叶变换莫尔法处理光栅图像，从而获得包含有水表面波的振幅的相位信息，再经适当的几何变换获得振幅信息。我们在垂直振荡装置上进行了不同激励频率和不同振幅的表面波的振幅测量。