Re: [ESPResSo-users] terminal velocity for LB fluid

[Owen Hickey]

The problem is that you slowly accelerate the fluid and continuously add momentum, without removing any. If you measure the relative velocity of the particle to the surrounding fluid that will reach a terminal velocity. You could also achieve a terminal velocity by confining the fluid in some way (like plates).

Hope that helps,

Owen

On Fri, Sep 27, 2013 at 5:12 AM, Vincent Ustach <address@hidden> wrote:

Hi all,

I am using the the sample script lb_fluid_coupling_gpu.tcl

I have modified the script to print the velocity each time the script records for the average. I have also increased the integrations to 500 steps per recording.

When the force density ext_force $fdragx $fdragy $fdragz is removed from the fluid, the particle accelerates beyond the expected terminal velocity of 0.1, even beyond the allowance for effective friction having a lower value lower than the bare friction (Alrich & Dunweg 1999).

Why is a terminal velocity not achieved?

Thanks,

--Vincent Ustach

--Vincent Ustach
  University of California, Davis

On Thu, Sep 26, 2013 at 8:11 PM, Vincent Ustach <address@hidden> wrote:

Hi all,

I am using the the sample script lb_fluid_coupling_gpu.tcl

I have modified the script to print the velocity each time the script records for the average. I have also increased the integrations to 500 steps per recording.

When the force density ext_force $fdragx $fdragy $fdragz is removed from the fluid, the particle accelerates beyond the expected terminal velocity of 0.1, even beyond the allowance for effective friction having a lower value lower than the bare friction (Alrich & Dunweg 1999).

Why is a terminal velocity not achieved?

Thanks,

--Vincent Ustach