sandbox/Antoonvh/test_sf.c

Test the structure function function

It seems to be off by a factor of two

#include "grid/octree.h"
#include "structure_function.h"

int main() {
  init_grid (128);
  vector v[];
  
  foreach() {
    v.x[] = x;
    v.y[] = 0.;
    v.z[] = 0.;
  }

  long2structure (stdout, v, 5000, L0/1.5, 50);

\mathbf{v} = \{x, 0\}

\delta v_{//} (l) = l cos(\theta)^2

average \delta v^2 over \theta

S_2(l) = \frac{3}{8}l^2

plot 'out' u 1:2 t 'data', 0.375*x**2 t 'analytical'

(script)

  foreach() {
    v.x[] = 0.;
    v.y[] = x;
  }
  
  long2structure (stderr, v, 5000, L0/1.5, 50);

\mathbf{v} = \{0, x\}

\delta v_{//} (l) = l sin(\theta)cos(\theta)

average \delta v^2 over \theta

plot 'log' u 1:2 t 'data', 0.125*x**2 t 'analytical'

(script)

}