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Simulation of less‐mobile porosity dynamics in contrasting sediment water interface porous media 
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下载免费PDF全文 Farzaneh MahmoodPoor Dehkordy Martin A. Briggs Frederick D. Day‐Lewis Amvrossios C. Bagtzoglou 《水文研究》2018,32(13):2030-2043
Considering heterogeneity in porous media pore size and connectivity is essential to predicting reactive solute transport across interfaces. However, exchange with less‐mobile porosity is rarely considered in surface water/groundwater recharge studies. Previous research indicates that a combination of pore‐fluid sampling and geoelectrical measurements can be used to quantify less‐mobile porosity exchange dynamics using the time‐varying relation between fluid and bulk electrical conductivity. For this study, we use macro‐scale (10 s of cm) advection–dispersion solute transport models linked with electrical conduction in COMSOL Multiphysics to explore less‐mobile porosity dynamics in two different types of observed sediment water interface porous media. Modeled sediment textures contrast from strongly layered streambed deposits to poorly sorted lakebed sands and cobbles. During simulated ionic tracer perturbations, a lag between fluid and bulk electrical conductivity, and the resultant hysteresis, is observed for all simulations indicating differential loading of pore spaces with tracer. Less‐mobile exchange parameters are determined graphically from these tracer time series data without the need for inverse numerical model simulation. In both sediment types, effective less‐mobile porosity exchange parameters are variable in response to changes in flow direction and fluid flux. These observed flow‐dependent effects directly impact local less‐mobile residence times and associated contact time for biogeochemical reaction. The simulations indicate that for the sediment textures explored here, less‐mobile porosity exchange is dominated by variable rates of advection through the domain, rather than diffusion of solute, for typical low‐to‐moderate rate (approximately 3–40 cm/day) hyporheic fluid fluxes. Overall, our model‐based results show that less‐mobile porosity may be expected in a range of natural hyporheic sediments and that changes in flowpath orientation and magnitude will impact less‐mobile exchange parameters. These temporal dynamics can be assessed with the geoelectrical experimental tracer method applied at laboratory and field scales. 相似文献
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A numerical modeling study is conducted to assess and gain a better understanding of the arching effects of field cemented tailings backfill (CTB). An integrated multiphysics model is developed that can illustrate and capture the changes in the material properties of CTB, consolidation behavior of CTB mass, and the shear behavior at the CTB/Rockwall interface. The predictive capability of the model has been successfully verified with comparisons of the predicted results with monitoring data taken from a series of field studies. The model is then used to simulate a series of applications that are relevant to CTB in practice. 相似文献
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三维地质建模具有直观、形象、便捷等优点,在地质、矿产、地下施工等领域有着突出贡献。COMSOL Multiphysics作为多物理场耦合模拟仿真软件,具备一定的三维建模能力。通过充分挖掘该软件自身潜力,结合Kriging插值方法,尝试建立了山西某井田的三维地质模型。研究结果显示,基于COMSOL Multiphysics的三维地质建模方法可实现地质体模型的缩放、旋转和平移等操作,生成地质剖切面图、透视图,展示地质体内部的各个细节。实例证明了COMSOL Multiphysics软件的三维地质建模能力及其在地质解译、矿产评估和多物理场求解等方面的应用价值。 相似文献
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饱和多孔介质的动力响应研究在众多工程领域具有重要意义。充分考虑孔隙率的变化规律与影响因素，有利于合理揭示饱和多孔介质的相关力学行为。为此，将动态孔隙率模型与用于表征饱和多孔介质动力特性的u-U-p型方程结合，构建相应的非线性力学模型，利用Comsol Multiphysis PDE求取相应的数值解，以此研究不同透水条件下，受谐波载荷激励的二维饱和土体的孔隙率、变形量及孔隙水压力的变化规律。结果表明：孔隙率的变化与土骨架的体应变及孔隙水压力直接相关，土体压缩过程中，孔隙率相应减小，土骨架与孔隙流体的相互作用增强，土体运动时所受阻力增大，其无量纲竖向位移小于孔隙率被视为常数时的情况，在此条件下，由于土体的变形量减小，其孔隙水压力也相对减小。故充分考虑动态孔隙率，有利于更加精确地研究等饱土体和多孔介质的相关力学行为。此外，土体上表面透水条件下，孔隙流体可以从土体表面自由排出，土骨架承受的载荷更大，与不透水条件相比，土体孔隙率、竖向位移、孔隙水压力等变化更为显著。 相似文献
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Using multiphysics computer codes has become a useful tool to solve systems of partial differential equations. However, these codes do not always allow for the free introduction of implicitly defined state functions when automatic differentiation is used to compute the iteration matrix. This makes it considerably more difficult to solve geomechanical problems using non-linear constitutive models. This paper proposes a method for overcoming this difficulty based on multiphysics capabilities. The implementation of the well-known Barcelona basic model is described to illustrate the application of the method. For this purpose, without including formulation details addressed by other authors, the fundamentals of its implementation in a finite element code are described. Examples that demonstrate the scope of the proposed methodology are also presented. 相似文献
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