Drainage under suction

Using the theory of hydrostatic foam stability [21, 26], the behaviour of foams in contact with fabrics was studied [181]. Under these conditions, the drainage of liquid from the foam occurs under the influence of the following processes 1) suction of liquid due to capillarity of high-dispersion foams 2) imbibition of foam by the capillary structure of fabrics. The production of foams with a controlled structure allows to achieve a more uniform application of a dye to a fabric. Foamer formulations were developed containing surfactants and a water-soluble polymer, which allow to achieve a minimum initial syneresis rate up to 10 m/s [182]. 

The water storage characteristics of several Minnesota peats in situ, as determined by Boelter (1964), were shown to vary markedly with peat type. Surface horizons of sphagnum moss peat had large pores and released about 80% of the water by volume at low suction (0.1 bar). In contrast, decomposed and herbaceous peats from horizons below 25 cm had small pores, although high porosity, and were not easily drained. They released only 25—35% water by volume under the same suction. These data emphasize that water table fluctuations in a peat profile do not in themselves indicate the quantity of water involved. Furthermore, peat types must be considered in drainage operations. 

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