/**
# Decaying two-dimensional turbulence
We solve the two-dimensional incompressible Euler equations using a
vorticity--streamfunction formulation. */
#include "grid/multigrid.h"
#include "navier-stokes/stream.h"
/**
The domain is square of size unity by default. The resolution is
constant at $256^2$. */
int main() {
init_grid (256);
run();
}
/**
The initial condition for vorticity is just a white noise in the range
$[-1:1]$ .*/
event init (i = 0) {
double a = 1. [0,-1];
foreach()
omega[] = a*noise();
}
/**
We generate images of the vorticity field every 4 timesteps up to
$t=1000$. We fix the colorscale to $[-0.3:0.3]$.
![Evolution of the vorticity](turbulence/omega.mp4)(autoplay loop) */
event output (i += 4; t <= 1000) {
output_ppm (omega, min = -0.3, max = 0.3, file = "omega.mp4");
}