# Test case for solid-solid drag

## Description

The case tests the solid-solid drag implementation. A closed domain is filled
with a continuous fluid, a light solid particle phase, and a heavy particle
phase. All phases are initially equally distributed. The particle phases start
to redistribute driven by buoyancy, i.e. the light particle phase goes up and
the heavy particle phase goes down. This redistribution is slowed down by the
solid-solid drag.

## Technical Information

* 2D
* Three phases: fluid, solid1, solid2
* Buoyancy, solid-continuous drag, solid-solid drag

## Pre-processing

None
