The effect of plastic rearrangements on the flow of two-dimensional wet foam

Abstract

The effect of the elementary plastic events on the flow behavior of the two-dimensional wet foam is investigated by quasistatic simulation on the bubble scale. The position where the plastic event occurs is traced by recording the coordinate at which two bubbles separate in the simulation. A localized shear band is found, and the width of this band increases with the increase of foam quality. From the displacement fields of these bubbles, it shows that the T1 plastic events can give rise to an increase in local bubble displacements due to the separation between these bubbles. The average relative pressure as well as normal stress difference of bubbles increases with the flow of foam in the initial elastic domain and then decreases as the elastic domain turns into the plastic domain. In the plastic domain, the plastic events rearrange the local structure of foam, which leads to decreasing both the average pressure and the normal stress difference. Additionally, the wall slip of foam is discussed in the simulation as well. The width of the localized shear band is narrower under the slip boundary condition. Meanwhile, the plastic events occurring between the first and second layers of bubbles change the pulling force of the films near the wall and cause an instantaneous increase in the slip velocity.