多孔介质固体颗粒粒径特征及膨胀作用对地下水孔隙尺度流场特征的影响

地下水孔隙尺度流场特征的研究对于深入理解地下水渗流、溶质运移具有重要意义.目前固体颗粒粒径特征不同时介质微观结构对孔隙尺度流场的影响尚不清楚.基于迭代重排算法构建了固体颗粒粒径分布特征、膨胀程度不同的多孔介质,基于此研究了固体颗粒平均粒径、粒径方差及膨胀作用对地下水流场特征的影响.结果表明,在介质孔隙率相同的条件下,固体颗粒平均粒径、粒径方差对多孔介质中流速的非均质性、速度概率密度分布等流场特征影响较小.而在同一介质中,当固体颗粒膨胀引起孔隙率减小时,平均粒径较小幅度的变化就会对以上流场特征产生显著影响.例如当固体颗粒膨胀程度增强时,粒径小幅度的增大,就会导致流场中优势流区和不流动区比例同时大幅度增加,流场非均质性显著增强,流速概率密度分布更加发散.

Radial mixing and segregation of granular bed bi-dispersed both in particle size and density within horizontal rotating drum

Taking simultaneous variations in both particle volume and density into account, the radial mixing and segregation of binary granular bed in a rotating drum half loaded were investigated by a 3D discrete element method. Then, based on the competition theory of condensation and percolation, radial segregation due to differences in particle volume and/or density was analyzed. The results show that if either percolation effect induced by volume difference or condensation effect induced by density difference dominates in the active layer of moving bed, separation will occur. Controlling the volume ratio or density ratio of the two types of particles can achieve an equilibrium state between percolation and condensation, and then homogenous mixture can be obtained. When the percolation balances with the condensation, the relationship between volume ratioand density ratiopresents nearly a power function. Scaling up a rotating drum will not affect the mixing degree of the granular bed so long as the volume ratio and density ratio are predefined.

HTAB在固液两相流中的减阻特性研究

为了探究添加HTAB下不同稠密粗细固体颗粒固液两相流的流动特征,采用直径为10 mm的不锈钢管作为实验管道,对影响固液两相流阻力特性的主要因素进行了研究。结果表明,影响固液两相流阻力特性的主要因素为固体质量浓度和固体颗粒粒径。通过改变固体质量浓度和颗粒粒径,观察添加表面活性剂对固液两相流的减阻特性影响情况,发现在相同表面活性剂质量分数以及颗粒粒径不变的情况下,摩擦阻力系数随着固体质量分数的增大而增大;在相同表面活性剂质量分数以及固体质量浓度不变的情况下,摩擦阻力系数随着颗粒粒径的增大而增大。