【作者】 余慧婷；

【导师】 张杰；

【作者基本信息】 暨南大学 ， 凝聚态物理， 2012， 硕士

【摘要】 本文参照土壤中的水分输运方程，建立沙中水分输运方程，在恒温恒湿条件下，通过实验及电导率测量的方法研究沙中水分输运的规律。将模拟计算结果与实验数据进行对比，确定沙中水分输运方程的参数，从而进一步完善沙中水分输运方程，为深入研究水在沙中的输运规律及应用提供参考。主要结论如下：1.根据恒定电路的欧姆定律，在含水均匀的情况下，电导率与含水率呈线性关系，当含水率小于0.12%时，电导率为零，主要原因在于这部分水被沙粒吸收，对电导率没有影响。2.金属网对实验的影响本实验通过分层测量玻璃管中的含水率探究水分输运规律，通过建立物理模型模拟计算金属网的存在所引起的误差。设上表面边长L₁=λ₁H,金属网孔的宽度L₂=λ₂L₁，其中，H为长方体模型的高。当λ₁≤0.1，λ₂=0.8时，金属网对电势的影响将大于0.53%范围内，对含水率的影响在0.3%范围内。3.均匀加入保水剂的沙的持水率最大，且持水率与保水剂的质量成正相关，无保水剂的沙的持水率最小。4.无保水剂掺入的沙中水分输运规律由总质量得出的含水率与沙中水分输运方程模拟计算的含水率符合较好，均方差小。由输运方程分层模拟计算得出的含水率与分层测量的等效含水率吻合较好。第一、二层均方差值较小，第三、四层均方差值较大。水分输运模型在总体或分层都可很好的描述沙中水分的输运。5.均匀掺入保水的沙中水分输运规律保水剂质量越大，含水率在开始的一段时间内下降越快，随着时间的增大，总含水率下降反而越慢。与无保水剂情况相比较，含水率较大。采用水分输运方程分层模拟计算得出的含水率与分层测量的等效含水率吻合较好，其中，第一、二层均方差值较小，第三、四层均方差值较大。与无保水剂情况相比较，均方差较大。水分输运模型在总体或分层都可很好的描述均匀掺入保水剂的沙中水分的输运。6.中间层掺入保水剂的沙中水分输运规律在中层掺入保水剂情况下，中间层的水分蒸发慢，含水率下降慢。与无保水剂的情况相比，中间层的含水率较大，与均匀掺入保水剂的情况相比，含水率较小。实验较好的验证了水分输运方程的有效性。更多还原

【Abstract】 In this paper, the law of water transporting in soil is cited to study how the water transportin sand under a constant temperature and humidity cases. The moisture content of sand andmixing super absorbent polymers can be measured by electric conductivity through the creationof physical models. We adjust the diffusion coefficient to make the simulation results consistentwith the experiment data. These conclusions can provide reference for further research of watertransport. The conclusions:1. The conductivity of wet sand is linear to the moisture content when water is evenly distributedin sand. If the moisture content below0.12%, the conductivity value decrease to zero. There isno effect to conductivity because the water is assimilated by sand.2. There is a cubic which side lengths both meetL₁=λ₁H,L₂=λ₂L₁. Ifλ₁is fixed, the error ofpotential is increase with increase ofλ₂, the error of moisture content is decrease with increaseofλ₂. The reason is that the big make the potential of the metal net surface diminish, but betterfor water transport. Ifλ₂is fixed, the error of potential and moisture content are diminish withdecrease ofλ₁. The reason is that the error of potential is distributed in a small region aroundmetal net, had no effect on the middle sand. If the size of physical model meetλ₁≤0.1andλ₂=0.8, error of potential and moisture content less than0.53%and0.3%.3. The water rate of the sand that super absorbent polymers evenly distributed is the biggestamong the three situation. The water rate and quality of super absorbent polymers are positivecorrelated.4. The law of water transport in sand.Moisture content changing with time is becoming smaller, the decreasing speed of themoisture content of glass B is less than glass A.The mainly reason is that the water affected by gravity downward transport, the bottom water of glass B is more than glass A, so there is lesswater to be evaporated, the moisture content of glass B is bigger than glass A. The curve of errorand diffusion parameter D0which determined by the total quality is smooth than determined byeach layer of moisture content.5. The law of water transport in sand with super absorbent polymers.The heavier the quality of super absorbent polymers is, the faster the speed of the decline ofthe moisture content is. The moisture content in this case is bigger than the sand without superabsorbent polymers. The greater the quality of super absorbent polymers, the bigger the diffusionparameter D0but the size and the quality of super absorbent polymers is out of multiples.6. The law of water transport in sand with super absorbent polymers in the middle layer.The super absorbent polymers in the middle layer affect the bottom water transport law. Themoisture content of simulation and the moisture content error between simulation andexperiment is about5by input parameters, so it is in good conformity.更多还原