For low Mach-number flows, the user must ensure the coherence between the reference values of physical quantities defined in the namelist
"Fluid_Properties" (temperature, density and molecular mass), the initial temperature field over the domain (defined here) and, if needed, the species mass fraction distribution defined in the namelist
"Species_Initialization" (if the gas is composed with multi-components).
Keep in mind that the reference value of thermodynamic pressure is calculated from the reference values of temperature, density and molecular mass of the fluid (see namelist
"Fluid_Properties").
The density field is then initialized from the fields of temperature (and species mass fractions if needed) by considering the thermodynamic pressure is uniform over the domain (low Mach-number hypothesis).