`Cavity Coupling`

Module: devtests.mechanics.cavity.run

Section author: Christoph Augustin <christoph.augustin@medunigraz.at>, Gernot Plank <gernot.plank@medunigraz.at> and Matthias Gsell <matthias.gsell@medunigraz.at>

This example provides pure mechanics and electromechanics examples on a simple ring geometry.

Problem Setup

This problem generates a simple ring mesh using the carputils.mesh.Ring class. The ring is tesselated into tetrahedra as shown below:

In all experiment types in this example, the top and bottom surfaces of the ring are constrained to lie in the same plane with Dirichlet boundary conditions, and an additional three nodes on the bottom ( $z=0$ ) surface are constrained such that free body rotation and translation is prevented. Two nodes on the x axis are prevented from moving in the y direction, and one node on the y axis is prevented from moving in the x direction:

Experiments

Several experiments are defined:

neumann - Apply a pressure to the endocardium with a Neumann boundary condition at successively higher increments
active-free - Run an active contraction simulation without constraints on cavity size or pressure
active-iso - Run an active contraction simulation with an isovolumetric cavity constraint
unload - Compute the unloaded reference state of the ring
unload-validate - Reinflate from the unloaded reference state, which should reproduce the original mesh

Other Arguments

Another key argument is the stress model. Three active stress models are available:

NPStress - The simple stress model from Nash and Panfilov
Rice - The more biophysically realistic model from Rice
FxStress - A very simple active stress model based on activation times and constructed with exponential functions