Liquid Migration

Willet liquid bridge model in MercuryDPM referred to as LiquidBridgeWillet (LiquidBridgeWilletSpecies, LiquidBridgeWilletInteraction). and LiquidMigrationWillet (LiquidMigrationWilletSpecies, LiquidMigrationWilletInteraction)

Wet cohesion is due to liquid bridges between particles in contact or close proximity. If the system is in the pendular regime (liquid fills less than 30 % of void space), liquid bridges form between particle pairs only; for higher liquid fraction, the three-particle liquid bridges or suspensions need to be considered. Liquid bridges between particle pairs typically have a range smaller than a particle diameter, so they are short-ranged. The liquid bridges form from liquid on the particles surface when two particles come into contact, but require a certain separation distance to separate again, so these forces are irreversible (hysteretic).

Complex liquid bridge model:

\( f_{ij}^{nc} = \frac{2\pi r_c \Gamma cos \theta}{ 1 + 1.05s \sqrt{r_c/V} + 2.5s^2 r_c/V} \)

where \( V \) is the bridge volume, \( r_c\) the average radius of curvature of the spheres, , \( \Gamma\) the surface tnesion of the liquid air interface and \( s\) the separation, \( \theta\) is the contact angle.

Header:

#include "Species/AdhesiveForceSpecies/LiquidMigrationWilletSpecies.h" 

Interaction force:

void LiquidBridgeWilletInteraction::computeAdhesionForce() 

Self Test: LiquidMigrationTwoSpeciesSelfTest.cpp

References:

1- R. Mani et. al., Liquid migration in sheared unsaturated granular media

2- S. Roy et. al., Liquid redistribution in sheared wet granular media