摘要：

The stability analysis of the delta-function model of infiltration yields a maximum wave-number for unstable disturbances, Mcrit, and a wave-number for maximum amplification, M*. The "column effect," i.e. the suppression of instability in laboratory columns, depends on Mcrit; and the dimensions of fingers in unstable flows can be expected to depend on M*. When instability is induced by a sudden jump of G, the water pressure gradient behind the wetting front, Mcrit and M* may be evaluated simply and directly. When, on the other hand, instability emerges during gradual increase of G, it is necessary to study the amplification of disturbances during the whole course of increase of G through positive values.

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