Experimental Studies of Wetting Front Instability Induced by Gradual Change of Pressure Gradient and by Heterogeneous Porous Media1
- I. White,
- P. M. Colombera and
- J. R. Philip2
The stability of infiltration flows in Hele-Shaw cells was examined. Flows were perturbed either by gradually increasing G, the pressure gradient behind the wetting front, or by heterogeneities in the cells. Two methods were used to increase G gradually through zero: (i) by allowing the air ahead of the front to be compressed by the flow, and (ii) by monotonically increasing the hydraulic conductivity of the cell with depth. In the other class of experiments, the flow was instantaneously perturbed by a step-increase in conductivity at selected depths.
It was found that Philip's (1975a, 1975b) stability analysis adequately predicted both the onset of instability and the wavelength of the initial disturbances. For quadratic increase in conductivity with depth the observed growth rate of disturbances was faster than expected from the linear theory.
Examination of the data of Peck (1965) and Hill and Parlange (1972) showed that Philip's analysis is also adequate for coarse sands.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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