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Re: [ESPResSo-users] LB as a thermostat

From: Owen Hickey
Subject: Re: [ESPResSo-users] LB as a thermostat
Date: Fri, 7 Mar 2014 15:07:16 +0100

Hey Roya,

1) I presume you have already called the lbfluid command to create the fluid. In this case the setting of a temperature using the lb thermostat should provide HI given reasonable parameters.
2) I find with lb it is often necessary to use kill_particle_motion just prior to initiating the lb fluid. If that doesn't work I would try with thermostat lb 0.0. If that still break try using a tiny friction: "lbfluid friction 0.0000001". The thermostat lb 0 just kills fluctuations while the friction being tiny should essentially kill the particle-fluid interaction.
3) You can print out the pressure of individual nodes using lbnode x_index y_index z_index pi or lbnode x_index y_index z_index pi_neq, which gives you the equilibrium and non-equilibrium part of the pressure tensor on that lb node. This will however be quite slow if you call it a lot but unfortunately an lbfluid print pi is not available (at least it's not in the user's guide).

Hope that helps,

On Fri, Mar 7, 2014 at 12:55 PM, roya moghaddasi <address@hidden> wrote:
Hello everybody,
I need to use thermostat lb in my program . At first, I ran my program with thermostat lj, then I delete "thermostat langevin 1.0 1.0" and write "thermostat lb 1.0" instead,
1.Is it enough to write just one line and have hydrodynamics in my system? 
2.I got the error " constraint violated by particle ....." with thermostat lb while I didn't face this error with thermostat langevin, why this happens? how can I solve this?
3. How can I  measure the pressure gradient in my system?
I would appreciate if someone can help me.

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