Fix bounce-back boundary conditions
Fix bounce-back boundary conditions

From the point of contact with the wall, propagate all three components
of the position with the reversed velocity. Refer to section 4.1 of

J. K Whitmer and E. Luijten, J. Phys. Cond. Mat. 22, 104106 (2010).
http://dx.doi.org/10.1088/0953-8984/22/10/104106

pdebuyl/RMPCDMD,laurensdeprez/RMPCDMD,pdebuyl-lab/RMPCDMD,laurensdeprez/RMPCDMD,pdebuyl/RMPCDMD,pdebuyl-lab/RMPCDMD