Syneresis gravitational

Another process which leads to HIPE instability is gravitational syneresis, or creaming, where the continuous phase drains from the thin films as a result of density differences between the phases. This produces a separated layer of bulk continuous phase and a more concentrated emulsion phase. The separated liquid can be located either above or below the emulsion, depending on whether the continuous phase is more or less dense, respectively, than the dispersed phase. This process has been studied by Princen [111] who suggests that it can be reduced by a number of parameters, including a high internal phase volume, small droplet sizes, a high interfacial tension and a small density difference between phases. 

Gravitational syneresis. Distribution of the foam multiplicity. In [247], Eq. (7.4.4) was solved for a vertical steady-state (dV/dt = 0) stagnant (U = 0) nonirrigated (q = 0) foam column under the condition that the foam multiplicity attains its minimum (Kmm) at the interface between the foam and the liquid (in the cross-section Z = 0). The following quadratic dependence of the foam multiplicity on the height was obtained ... 

Gravitational syneresis problems in a somewhat different setting were also studied in [377, 383],... 

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