turbulence.c

Decaying two-dimensional turbulence

We solve the two-dimensional incompressible Euler equations using a vorticity–streamfunction formulation.

#include "navier-stokes/stream.h"

The domain is square of size unity by default. The default resolution is constant at 256^2 but can be change using command line arguments.

int main (int argc, char * argv[]) {
  init_grid (argc > 1 ? atoi(argv[1]) : 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 (cpu)
    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

event output (t += 1; t <= 1000) {
#if !BENCHMARK
  output_ppm (omega, min = -0.3, max = 0.3, file = "omega.mp4");
#endif
}

On GPUs we have the option to display the vorticity field in real time.

#if _GPU && SHOW
event display (i++)
  output_ppm (omega, min = -0.3, max = 0.3, fps = 30, fp = NULL);
#endif