Bin-centred difference scheme
From Atomix
For a bin-centred difference scheme:
- start at bin n = (nmax / 2) + 1
- start with [math]\displaystyle{ \delta }[/math] = 1
- if [math]\displaystyle{ \delta }[/math] is even compute the second order structure function D(n,[math]\displaystyle{ \delta }[/math]) as the segment mean of the square of the velocity difference between the bins separated by distance [math]\displaystyle{ \delta }[/math]r0 centered around bin n:
D(n, [math]\displaystyle{ \delta }[/math]) = [math]\displaystyle{ \langle }[/math] [v’(n+([math]\displaystyle{ \delta }[/math]/2), t) - v’(n-([math]\displaystyle{ \delta }[/math]/2), t)]2 [math]\displaystyle{ \rangle }[/math]
where the angled brackets indicate the mean across all t for the data segment yielding a velocity difference after the application of the Level 1 QC criteria - if [math]\displaystyle{ \delta }[/math] is odd compute the second order structure function D(n,[math]\displaystyle{ \delta }[/math]) as the segment mean of the mean of the square of the velocity difference between the bins separated by distance [math]\displaystyle{ \delta }[/math]r0 centered on the upper and lower extent of bin n:
dv'lo(n, [math]\displaystyle{ \delta }[/math], t) = v’(n+floor([math]\displaystyle{ \delta }[/math]/2), t) - v’(n-ceil([math]\displaystyle{ \delta }[/math]/2), t)
dv'hi(n, [math]\displaystyle{ \delta }[/math], t) = v’(n+ceil([math]\displaystyle{ \delta }[/math]/2), t) - v’(n-floor([math]\displaystyle{ \delta }[/math]/2), t)
where ceil and floor indicate the upper and lower integer value respectively, then
D(n, [math]\displaystyle{ \delta }[/math]) = [math]\displaystyle{ \langle }[/math] [dv'lo(n, [math]\displaystyle{ \delta }[/math], t)2 + dv'hi(n, [math]\displaystyle{ \delta }[/math], t)2] / 2 [math]\displaystyle{ \rangle }[/math]
the angled brackets again indicating the mean across all t in the data segment yielding a velocity difference after the application of the Level 1 QC criteria - increment [math]\displaystyle{ \delta }[/math] and repeat steps until [math]\displaystyle{ \delta }[/math] = nmax
- increment n and repeat steps until n + (nmax / 2) exceeds the bin number for which valid v’ are available