tracer4.c

Tracer advection in a accelerating frame of reference

Tracer advection in a accelerating frame of reference

The concergence test

Variance test (advection of noise)

set xr [8:512]
set yr [1e-5:10]
set grid
set logscale x 2
set logscale y
set size square
set xlabel 'N'
set ylabel 'L_1'
plot 'out' t 'Data', 1e6*x**(-4) t '4th order'

Convergence (script)

reset
set xr [8:512]
set yr [0:40]
set grid
set logscale x 2
set size square
set xlabel 'N'
set ylabel 'Sum of squares'
plot 'out' u  1:3 t 'Data', 33.333 t 'Perfect noise'

Advection of noise (script)

#include "nsf4t.h"
#include "view.h"

scalar s[], n[], * tracers = {s, n};
double ax = 0.1, ay, uo = 0.5, tend;

int main() {
  foreach_dimension()
    periodic (left);
  L0 = 10;
  X0 = Y0 = -L0/2;
  tend = (-uo + sqrt(sq(uo) - 2*ax*-L0))/(ax); // ABC formula
  ay = 2*L0/sq(tend);
  const vector av[] = {ax, ay};
  a = av;
  for (N = 16; N <= 256; N *= 2)
    run();
}

event init (t = 0) {
  foreach_face(x)
    u.x[] = uo;
  foreach_vert() {

Basilisk C parse error near

foreach_vert() {</div></div> ~~~c     s[] = exp(-sq(x) - sq(y)); ~~~ <div class=error id=56><div id=msg_logo><img src=/img/error.png></div><div id=msg_label> constant field 'n' must be declared (const)</div></div> ~~~c     n[] = noise();   } }  event mover (t += 0.5) {   squares ("s", min = -0.1, max = 1.1);   save ("s.mp4");   squares ("n", min = -1, max = 1, map = cool_warm);   save ("n.mp4");   // There is an issue with these:   // output_ppm (s, file = "s.png", n = 300);   // output_ppm (n, file = "n.mp4", n = 300, min = -1, max = 1); }  event stop (t = tend) {   event ("mover");   double e = 0, E = 0;   foreach_vert() { ~~~ <div class=message id=74><div id=msg_logo><img src=/img/warning.png></div><div id=msg_label> Basilisk C parse error near

foreach_vert() {

    e += dv()*fabs(s[] - exp(-sq(x) - sq(y)));
    E += dv()*sq(n[]);
  }
  printf ("%d %g %g\n", N, e, E);
}