Fluid density is constantly present in the equations of fluid mechanics.

The mass per unit volume is the ratio of the mass by its volume the unit used is Kg/m3

For purists, I met some, I specify that the density of a liquid is the ratio of the mass per unit volume of the material on the water mass per unit volume. (for a gas, the ratio will be taken with the mass per unit volume of the air) This gives us a dimensionless number, without unity, which is the density of the material

Exemple: the water mass per unit volume is 1000 Kg/m3

the mass per unit volume of the oil is 800 Kg/m3

the density of the oil is=800/1000= 0.8

Density of water=1000/1000= 1

With ** Mecaflux** standard

The density of the liquid or gas is provided in the fluid editor:

The editor gives density , mass per unit volume of the fluid selected depending on the temperature but also its viscosity and saturation vapor pressure.