POLYFLOW - How to simulate the transient flow out of a capillary under an applied force?
Flow experiments with capillary often involve the application of a constant force (load). How can this be simulated with POLYFLOW, while incorporating the downward motion of the weight?
This is typically a transient flow case which could be simulated by considering a multi-domain approach. A first subdomain would be the fluid region (possibly divided into two subdomains for remeshing purposes); relevant rheology must be defined and boundary conditions have to be selected, togeather with a moving interface with the above subdomain. The upper subdomain plays the role of the weight. It should receive a very high viscosity so that its shape wil not deform; density and gravity have to be selected such that they produce the required load when combined with the volume of the subdomain. That "load" subdomain must also see the moving interface conditoins, while vanishing forces can be imposed elsewhere.
In general, slipping velocity boundary conditions should be preferred instead of zero velocity; this will prevent undesired deformations.
The concept is illustrated on the following image: