Air entrainment in hairy surfaces

Falling jet of dry granular material in water

“…This long-term behaviour leads to a straight interface between the wet grains and the dry grains whose scaling of the slope matches the scaling found by Nasto et al. (2016). The slope of the dry–wet interface is given by the following equation: In the following, we compare the analytical model to the experimental results obtained with the 2D porous media.…”

“…A transition is observed, characterized by a change of the exponent describing the evolution of with : For large plunging speeds (), the exponent matches well with the prediction of Nasto et al. (2016), who neglected the capillary effects and assumed a horizontal impregnation in the porous material. For small plunging speeds (), we find an exponent similar to the one reported for wetting systems in figure 10( a ), which suggest that this exponent does not depend on the capillary effect.…”

“…In this limit, the analytical solution reduces to This power law also corresponds to the prediction proposed by Nasto et al. (2016) for hairy surfaces plunged vertically into a liquid. In their configuration, Nasto et al.…”

“…Furthermore, in the case of a porous material, the isotropy of the medium does not constrain an orientation of the fluid front, contrary to the case of the hairy surfaces studied recently by Nasto et al. (2016).

Figure 1.Time series of a free semi-2D granular jet penetrating into a water bath.

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“…In their configuration, Nasto et al. (2016) assume that because the fibers are oriented horizontally, the induced lateral flows are only horizontal, in the direction of the fibers. Equation (C5) is plotted in figure 26( b ) and captures well the evolution of the impregnation front with the plunging speed at large depth.…”