Critical absolute permeability

Figure 5. The critical absolute permeability necessary to sustain the stability of a static foam as a function of liquid saturation. Calculations are for the constant-charge electrostatic model.

The message from Figure 8 is that static lamellae are stable to small disturbances until a critical capillary pressure is attained then coalescence is catastrophic. In porous media, the liquid saturation, absolute permeability, and surface tension control this critical capillary pressure through the Leverett J-function (75). Of course, static lamellae may coalesce at lower capillary pressures, if they are subjected to large disturbances. Figure 8 also reveals that static lamellae in equilibrium with the imposed capillary pressure are amazingly thin. 

That is, viewed at the other angle on this subjeet, it follows that it is also possible to calculate, by applying Eq. (79), the critical (or the smallest) radius for the thermal explosion, below which the thermal explosion of a similar body of a powdery chemical of the TD type, including every gas-permeable oxidatively-heating substance, for which the individual values of the variables, a, b, and cf ., apart from the constant, A T, in Eq. (79) are fixed, placed in the atmosphere maintained at an arbitrary temperature. T cannot occur absolutely, For a concrete example, refer to (2) of Subsection 8.4,4. 

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