Longitudinal and transverse dispersion coefficients in unsaturated plainfield sand
Longitudinal and transverse dispersion coefficients in unsaturated plainfield sand
复制标题
非饱和平原砂的纵向和横向分散系数
DOI：
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发表时间：
1978
期刊：
影响因子：
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通讯作者：
W. R. Gardner
中科院分区：
文献类型：
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作者：
D. Yule;W. R. Gardner
在长23 cm的C层平原砂垂直非饱和柱中，测定了纵向和横向弥散系数（DL和Dτ）与孔隙水流速（φ）和有效扩散系数（De）的关系，其中φ为0.01 <φ <0.28cm/min。土柱上的流入和流出控制系统由多排多孔陶瓷管组成，多孔陶瓷管具有单独的可调节压力控制装置。在整个柱中实现均匀的流入和流出，并且在每个实验期间保持恒定的流速。对所产生的横向扩散的分析表明，设备引起的分散的影响<10%。DL（cm ~ 2/min）与λ（cm/min）呈线性相关（DL = 0.216 λ + 0.0032; r ~ 2 = 0.90）。稍大的DL被发现在实验中与H2O取代Cl比在实验中与Cl取代H2O。在最低的Δ R处的DL比De大2个数量级。DT（cm 2/min）基本上与λ无关（DT = 0.0035 λ + 0.0031; r2 = 0.15），并且在研究的最低λ下比De大约2个数量级。在流出处示踪剂的扩散与λ成反比，横向分散使流入处的浓度峰值在L = 23 cm和λ = 0.01 cm/min处降低了84%。DL/DT比与λ成正比，范围为λ 1（λ = 0.01 cm/min）至λ 20（λ = 0.28 cm/min）。
The relationship between the longitudinal and transverse dispersion coefficients (DL and Dτ) and the pore water velocity (υ) and the effective diffusion coefficient (De) was determined for 0.01 < υ < 0.28 cm/min in a vertical unsaturated column (L = 23 cm) of C horizon Plainfield sand. The inflow and outflow control systems on the soil column consisted of rows of porous ceramic tubes with individual adjustable pressure controls. Uniform inflow and outflow were achieved across the column, and υ was maintained constant during each experiment. An analysis of the transverse spread produced indicated that the effect of apparatus-induced dispersion was <10%. DL (cm2/min) was linearly related to υ (cm/min) (DL = 0.216υ + 0.0032; r2 = 0.90). Slightly larger DL was found in experiments with H2O replacing Cl than in experiments with Cl replacing H2O. DL at the lowest υ was 2 orders of magnitude greater than De. DT(cm2/min) was essentially independent of υ(DT = 0.0035υ + 0.0031; r2 = 0.15) and was about 2 orders of magnitude greater than De at the lowest υ studied. The spread of tracer at the outflow was inversely proportional to υ, and transverse dispersion had reduced the concentration peak of the inflow by 84% at L = 23 cm and υ = 0.01 cm/min. The ratio DL/DT was proportional to υ and ranged from ∼ 1 (υ = 0.01 cm/min) to ∼20 (υ = 0.28 cm/min).