Page 74 - 2017地大报告电子书

2017

sizes of silica sand in mean diameter 1.075

mm, 1.475 mm, 1.85 mm, 2.5 mm and
3.17 mm. Both pre-Darcy flow and post

Darcy flow were identified but no obvious
linear flow was observed, the Reynolds

number of two flow regime are different
with different grain sizes. Relative error was

used to evaluate the experimental data and
obtain that the values of Reynolds number

at the demarcation point are 3.90, 7.08, 9.1
and 10.78. The values of Reynolds number of two flow regime increased gradually as the particle

diameter increased. A new Reynolds number defined as ratio of inertia term and viscous term in
Forchheimer equation can lead to a single criterion for determining the limit of validity of Darcy

law. The recommended critical Reynolds number for non-Darcy flow is equal to 0.1, where the
error of neglecting inertial effects in the hydraulic gradient will be less than 10%.

论文链接：https://doi.org/10.1016/j.ijheatmasstransfer.2016.08.085

5.Determination of the saturated film conductivity to improve the EMFX model in
describing the soil hydraulic properties over the entire moisture range
作 者 : Wang Yunquan*; Ma Jinzhu; GuanHuade; Gaofeng Zhu.

JOURNAL OF HYDROLOGY 卷 : 549 页 : 38-49 出版年 : JUN 2017
摘要：Difficulty in measuring hydraulic conductivity, particularly under dry conditions,

calls for methods of predicting the conductivity from easily obtained soil properties. As a
complement to the recently published EMFX model, a method based on two specific suction

conditions is proposed to estimate saturated film conductivity from the soil water retention curve.
This method reduces one fitting parameter in the previous EMFX model, making it possible to

predict the hydraulic conductivity from the soil water retention curve over the complete moisture
range. Model performance is evaluated with published data of soils in a broad texture range

from sand to clay. The testing results indicate that 1) the modified EMFX model (namely the
EMFX-K model), incorporating both capillary and adsorption forces, provides good agreement

with the conductivity data over the entire moisture range; 2) a value of 0.5 for the tortuosity
factor in the EMFX-K model as that in the Mualem’s model gives comparable estimation of

the relative conductivity associated with the capillary force; and 3) a value of − 1.0 × 10 − 20

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