# Physical properties¶

Specify physical constants. How this is done depends mostly on your choice of multi phase solver (see Multi phase solver). A single phase example:

physical_properties:
g: [0, 0, 0]
nu: 0.001
rho: 1.0

g

The acceleration of gravity given as a list of numbers. The length of the list must match the number of spatial directions, e.g. 2 or 3. Use [0, -9.81] in 2D and [0, 0, -9.81] in 3D for “standard” gravity.

## Single phase properties¶

nu

The kinematic viscosity

rho

The density of the fluid, defaults to 1.0.

## VOF two phase properties¶

nu0, rho0

The kinematic viscosity and density of fluid 0

nu1, rho1

The kinematic viscosity and density of fluid 1

For a water/air simulation fluid 0 is typically water and corresponds to VOF colour function value 1.0 while fluid 1 is typically air and corresponds to VOF colour function value 0.0.

## Variable density properties¶

nu

The kinematic viscosity of both fluids (single value)

rho_min, rho_max

The range of allowable densities. Give one number for each of these settings.