Numerical simulation of benzene transport in shoreline groundwater affected by tides under different conditions

● An approach for assessing the transport of benzene on the beach was proposed. ● The behavior of benzene in the subsurface of the beach was impacted by tide. ● Tidal amplitude influenced the travel speed and the benzene biodegradation. ● Hydraulic conductivity had the impact on plume residence time and biodegradation. ● Plume dispersed and concentration decreased due to high longitudinal dispersivity. The release and transport of benzene in coastal aquifers were investigated in the present study. Numerical simulations were implemented using the SEAM3D, coupled with GMS, to study the behavior of benzene in the subsurface of tidally influenced beaches. The transport and fate of the benzene plume were simulated, considering advection, dispersion, sorption, biodegradation, and dissolution on the beach. Different tide amplitudes, aquifer characteristics, and pollutant release locations were studied. It was found that the tide amplitude, hydraulic conductivity, and longitudinal dispersivity were the primary factors affecting the fate and transport of benzene. The tidal amplitude influenced the transport speed and percentage of biodegradation of benzene plume in the beach. A high tidal range reduced the spreading area and enhanced the rate of benzene biodegradation. Hydraulic conductivity had an impact on plume residence time and the percentage of contaminant biodegradation. Lower hydraulic conductivity induced longer residence time in each beach portion and a higher percentage of biodegradation on the beach. The plume dispersed and the concentration decreased due to high longitudinal dispersivity. The results can be used to support future risk assessment and management for the shorelines impacted by spill and leaking accidents. Modeling the heterogeneous beach aquifer subjected to tides can also be further explored in the future study.     

Hot water flushing for immiscible displacement of a viscous NAPL

Thermal remediation techniques, such as hot water flooding, are emerging technologies that have been proposed for the removal of nonaqueous phase liquids (NAPLs) from the subsurface. In this study a combined laboratory and modeling investigation was conducted to determine if hot water flooding techniques would improve NAPL mass removal compared to ambient temperature water flushing. Two experiments were conducted in a bench scale two-dimensional sandbox (55 cmx45 cmx1.3 cm) and NAPL saturations were quantified using a light transmission apparatus. In these immiscible displacement experiments the aqueous phase, at 22 degrees C and 50 degrees C, displaced a zone with initial NAPL saturations on the order of 85%. The interfacial tension and viscosity of the selected light NAPL, Voltesso 35, are strongly temperature-dependent. Experimental results suggest that hot water flooding reduced the size of the high NAPL saturation zone, in comparison to the cold water flood, and yielded greater NAPL mass recovery (75% NAPL removal vs. 64%). Hot water flooding did not, however, result in lower residual NAPL saturations. A numerical simulator was modified to include simultaneous flow of water and organic phases, energy transport, temperature and pressure. Model predictions of mass removal and NAPL saturation profiles compared well with observed behavior. A sensitivity analysis indicates that the utility of hot water flooding improves with the increasing temperature dependence of NAPL hydraulic properties.     

华北城市地区潜水中主要离子含量变化的反应途径模拟

近三十年来，由于污染，华北城市地区潜水中主要离子如ＣＡ＾２＋、Ｍｇ＾２＋等含量逐年升高，影响工农业生产，本采用反应途径模拟的方法对上述情况进行了研究，作共设计了７种反应途径，分别模拟了含碳酸盐或硅酸盐、铝硅酸盐较丰富地区地下水中盐效应和ＣＯ２分压升高对基主要离子含量的影响，模拟过程中考虑了２２种化学反应，３３种存在形式（包括气体、固体）。结果表明，盐效应和ＣＯ２分压升高对地下水中Ｃａ＾２＋、Ｍ     

重力作用下尘粒运动的数值解法

提出了重力作用下尘粒运动的数值解法。依据尘粒的重力、浮力及所受到的阻力推出了尘粒自然沉降时的运动方程。当尘粒的运动在斯托克斯领域内时采用理论公式求解其运动轨迹,当尘粒的运动进入非斯托克斯领域内时,提出了修正斯托克斯公式的方法以达到用理论公式来近似模拟该领域内的尘粒自然沉降运动     

冲裁件图形输入系统功能模块的设计

提出了面素拼合辅以线辅入法。其中所设计的每一基本面素均以参软化定义方式存在于用户界面，而以数字模型方式存在于计算机内。在面素的拼合运算(布尔运算)中，提供交、并、差等3种形状算子。参加布尔运算面素可为2个封闭的二维(2D)任意多边形，其交点可有多个(2个以上)。同时提供以逐条线段输入图形的方法。从而提高了系统的工作效率及输入复杂图形的能力。     

横门围垦对邻近海域水环境影响的数值模拟

用二维水动力数值模型,模拟了横门围垦工程对邻近海域水环境的影响。计算结果表明,工程后流速的改变幅度在-10.15～ 10.03cm/s之间,平均为-3.39cm/s。水位的改变幅度在-5.24～ 8.85cm之间,平均为-0.16cm,大潮期间落潮最大流速时水位的变化幅度,稍大于涨潮最大流速时的变化幅度。围垦工程完成后,邻近海域浅滩处的流速进一步降低,有利于促进淤积,加快浅滩成围速度,而深槽处的流速则略有提高,对河道泄洪没有太大影响。邻近海区水位低潮时将略有下降,高潮时将略有上升,但变化不大,最大不超过10cm,平均不到1cm。     

烟道内冲灰水喷雾烟气脱硫过程中传热传质的数值研究

通过数值建模研究了各项参数对喷雾反应段内吸收效率的影响，重点考察了雾滴初始粒径、雾滴初始速度、烟气入口温度、SO2入口浓度、喷雾反应段长度、液气比对吸收效率的影响。研究表明，雾滴初始粒径、SO2入口浓度、喷雾反应段长度、液气比是影响吸收效率的重要因素，而雾滴初始速度、烟气入口温度对吸收效率的影响不大。     

采用薄膜模型模拟三维板料成形过程

此文基于有限变形理论建立了三维金属板料成形过程的弹塑性有限元数学模型。数学模型采用物质坐标系中的Total Lagrange描述、J_2型本构方程、等向强化假设,考虑了板料的厚向异性,对于金属板料与模具的摩擦采用近似的库仑摩擦定律以改善计算的收敛性。为简化计算采用薄膜单元。采用根据此模型编制的程序模拟了机油收集器基本件的成形过程,并与实验结果进行了对比。     

广东区域酸雨污染模拟研究

运用数值模拟方法，使用一年365日的风速资料、12个月的降水资料和环境监测资料以及年平均的污染源资料，对广东地区的酸雨污染进行了较细致的分析。结果认为，以日为基础的累积计算，对于提高模拟酸雨污染的能力是很有帮助的。广东省的酸雨污染主要是由自身排放的污染物造成，外来的污染是次要的，在广东边界地区发现受到外省污染的显著痕迹。     

Influence of surfactant-facilitated interfacial tension reduction on chlorinated solvent migration in porous media: observations and numerical simulation

The ability of a multiphase flow model to capture the migration behavior of chlorinated solvents under conditions of surfactant-facilitated interfacial tension (IFT) reduction is assessed through comparison of model predictions with observations from controlled laboratory experiments. Tetrachloroethene (PCE) was released in two-dimensional saturated systems, packed with sandy media that incorporated rectangular lenses of capillary contrast. Spatially uniform interfacial tension conditions were created in the tanks by pre-flushing the porous medium with either Milli Q water or an aqueous surfactant solution. Experimental observations showed that surfactant-facilitated IFT reductions substantially lowered capillary resistance to the vertical downward migration of PCE and enabled PCE to enter finer grained, less permeable lenses that were not penetrated in the absence of surfactant. An immiscible flow model was used to simulate the conditions of the laboratory experiments. Under higher IFT conditions (47.5 and 5 dyn/cm), the model could successfully predict the general migration behavior of the organic liquid. Model predictions, however, exhibited poorer agreement with observed migration pathways under low IFT conditions (0.5 dyn/cm). In all cases, the predicted PCE distributions were influenced by selection of the parametric model for capillary retention and relative permeability. Simulated migration rates were more consistent with observed behavior when the Brooks-Corey/Burdine model was employed. For low interfacial tensions, improved predictions of migration pathways were obtained through grid refinement and incorporation of small-scale packing variability. Simulations highlight the substantial sensitivity of model predictions to the capillary pressure-scaling factor, grid resolution, and small-scale porosity variations at interfaces of permeability contrast under reduced IFT conditions.