varying the viscosity of the fluid in a Lattice-Boltzmann simulation
 

Hello,

I am quite new using Lattice-Boltzmann methods for solving fluid dynamics
(I am using LB3D).
I would like to vary the dynamic viscosity of my fluid. In LB simulations, kinematic viscosity is directly connected to the relaxation time scale chosen
normally as a constant equal to 1.
The density of fluid is introduced through a parameter amass_r corresponding (as presented) to the mass of fluid and its value is usually chosen as equal to 1.
What is the connection between this parameter amass_r and the physical
mass density of the fluid ?
How can I practically vary the dynamic viscosity of my fluid with LB methods ??

Thank you very much for your answers,

Best wishes

Fr.