Barry Smith <[email protected]> writes: >> On May 6, 2016, at 5:09 PM, Paul Stephen Urbanczyk <[email protected]> >> wrote: >> >> However, this raises another question: shouldn't the coordinates behave >> differently than other field variables? In other words, shouldn't the >> periodic ghost points at the left end have coordinates (0-h) and (0-2h), >> rather than (1-h) and (1-2h)? And, at the right side, shouldn't the >> x-coordinates be 1 and 1+h? > > I don't know. But I believe they should not; periodic boundary > conditions can be interpreted as having the domain [0,1) connected > at the two ends so there would never be coordinates less than 0 or > 1 or larger. Another way, I think, of saying the same thing is that > if you take a point x in domain and add some positive distance d > then the coordinate of the result is give by fractionalpart(x + d) > something similar can be done for subtracting some distance.
Additionally, making up coordinates for ghost points is not well-defined for non-uniform or distorted grids.
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