hello, Could anyone tell me what is the difference between cyclic and periodic boundary conditions? Thanks in advance Regards Hadi

Think of an O-grid in 2-D. There is one set of grid-lines which are closed; the first and last point on these lines are the same. You need cyclic conditions; its not really a boundary. For example if the grid index that goes around is i, and it ranges from 1 to imax, then u(1,j) = u(imax,j) for all j. Also in a finite difference scheme, if you need u(i-1,j) for i=1, then it will be u(imax-1,j). You get the idea.

A function is periodic if

u(x+L) = u(x)

Note that it is defined in all of R, the real number set. But it is enough to compute it in say [0,L]. When you apply some finite difference or your favourite scheme, you may need values outside [0,L]. Then you make use of the periodic condition to get these values.

Thank you praveen for the explanation Could you please tell me the definition of these two boundary conditions in the case of LES turbulent channel flow? regards Hadi