Lees and Edwards suggested a method to combine laminary flow with periodic boundaries in the direction:

Here are in language-independent form, the appropriate code parts for PBC and NIC:

// Periodic boundary conditions: // round(float) is the integer next to float // L is the cell side length; note that x,y,z vary between -L/2 and L/2 // t is the elapsed time // gamma is the shear rate cz=round(z/L) cx=x-cz*gamma*L*t x=cx-round(x/L)*L y=y-round(y/L)*L z=z-cz*L .....

// Nearest image convention: delx=x(j)-x(i) ... cz=round(dz/L) cdelx=delx-cz*gamma*L*t delx=cdelx-round(cdelx/L)*L dely=dely-round(dely/L)*L delz=delz-cz*L ...

This is the procedure for a single time step:

- Compute all forces, applying the nearest image convention
- Integrate the equs. of motion for
- Perform a least squares fit to a linear velocity profile,
determining and such that

(8.19) - Apply a simple thermostat by adjusting all
such that

(8.20) - Compute the stress tensor element

(8.21)

(8.22) |

F. J. Vesely / University of Vienna