A simple model for two or three fluids (e.g. liquid, gas, solid) in 2D, with different densities and viscosities. Includes models for buoyancy and surface tension.
The flow is assumed to be incompressible, so a vorticity equation is evolved for the momentum equation and no pressure equation is needed. Uses Arakawa's 2nd-order method to advect the vorticity, and upwinding with regularised anti-diffusion to advect the fluid type and track the location of boundaries between fluids.
Compiled with BOUT++ version 4.0
A test of the handling of surface tension is a stationary bubble. This should produce no flows, but numerically parasitic flows are observed.
$ ./two-phase-flow -d bubble $ python bubble.py
A boundary between two viscous fluids is initially perturbed. The frequency and damping rate of the resulting oscillation can be compared to analytic theory and previous results
$ python capillary.py
Simple flow of a single fluid in a pipe. Starts with an initial flow which damps due to viscosity. Includes no-slip boundary conditions on the walls, using Thom's formula.
input in pipe directory
Models air, water and sand with a simple model. A pile of sand in the middle of the domain acts to break waves in the water around it.
Note that because the sand is evolved as a simple fluid, it slowly collapses. A large viscosity is used to slow down the rate at which this happens.
input in three-fluid