[ESPResSo-devel] [bug #39568] LB stress tensor calculation is wrong

[Ulf Schiller]

URL:
  <http://savannah.nongnu.org/bugs/?39568>

                 Summary: LB stress tensor calculation is wrong
                 Project: ESPResSo
            Submitted by: uschiller
            Submitted on: Thu 25 Jul 2013 04:28:45 PM GMT
                Category: Simulation core
                Severity: 3 - Normal
                  Status: None
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                 Release: None
           Fixed Release: None

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Details:

The calculation of the LB stress tensor is wrong as it uses equations from
Duenweg&Ladd while the basis used in ESPResSo is not the one from
Duenweg&Ladd. The correct expressions are (double check recommended):

pi_xx = (2.*(m0 + m4) + m6 + 3.*m5)/6.;
pi_yy = (2.*(m0 + m4) + m6 - 3.*m5)/6.;
pi_zz = (m0 + m4 - m6)/3.;

pi_xy = m7
pi_xz = m8
pi_yz = m9





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