Re: Problem with LB parameters in EspressoMD units

[Ulf D Schiller]

The basic units for LB are the lattice spacing a, the fluid time step h,
and the density \rho_0. To keep the fluctuating LB algorithm stable, one
would normally determine a from the characteristic length scale, h from
the kinematic viscosity, and \rho_0 from the thermal energy scale, i.e.,

R = \hat{R} a
\nu = \hat{\nu} a^2/h
kT = \hat{kT} rho_0 a^5/h^2

Note that the mass scale sets the amplitude of thermal fluctuations.

Once you have chosen \hat{\nu}, the diffusion coefficient can be
calculated from the Schmidt number (Sc=\nu/D).

Hope this helps,
Ulf

On 8/16/21 5:27 AM, Ahmad Reza Motezakker wrote:
> Dear All,
> 
> 
> Hope you all had a good summer. 
> 
> I have a  system of polymers coupled to LB fluid. I have done unit
> conversions from SI to MD units considering the shape of particles
> (polymers with almost stiff bonding) and the fluid which is water.
> 
> Calculating LB parameters such as density and kinematic viscosity, a
> large number comes up for kinematic viscosity. I really do not know
> would it be correct to put such numbers in or not. I really appreciate
> if you help me with that. I have attached to procedure of unit
> converting to this email. 
> 
> 
> Best regards,
> 
> Ahmad Reza
> 

-- 
ULF D. SCHILLER
ASSISTANT PROFESSOR, MATERIALS SCIENCE AND ENGINEERING
College of Engineering, Computing and Applied Sciences
https://www.clemson.edu/cecas/
Clemson University

299C Sirrine Hall
Clemson, SC 29634
o 864-656-2669
uschill@clemson.edu
https://www.clemson.edu/
https://cecas.clemson.edu/compmat/