Colliding and merging planets (C)

This example integrates a densely packed planetary system which becomes unstable on a timescale of only a few orbits. The IAS15 integrator with adaptive timestepping is used. The bodies have a finite size and merge if they collide. Note that the size is unphysically large in this example.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <math.h>
#include "rebound.h"

void heartbeat(struct reb_simulation* r);

int main(int argc, char* argv[]){
struct reb_simulation* r = reb_create_simulation();
r->dt                   = 0.01*2.*M_PI;                // initial timestep
r->integrator           = REB_INTEGRATOR_IAS15;
r->collision            = REB_COLLISION_DIRECT;
r->collision_resolve    = reb_collision_resolve_merge;        // Choose merger collision routine.
r->heartbeat            = heartbeat;

struct reb_particle star = {0};
star.m = 1;
star.r = 0.1;

int N_planets = 7;
for (int i=0;i<N_planets;i++){
double a = 1.+(double)i/(double)(N_planets-1);        // semi major axis in AU
double v = sqrt(1./a);                     // velocity (circular orbit)
struct reb_particle planet = {0};
planet.m = 1e-4;
planet.r = 4e-2;                     // radius in AU (it is unphysically large in this example)
planet.lastcollision = 0;                // The first time particles can collide with each other
planet.x = a;
planet.vy = v;
}
reb_move_to_com(r);                // This makes sure the planetary systems stays within the computational domain and doesn't drift.

reb_integrate(r, INFINITY);
}

void heartbeat(struct reb_simulation* r){
if (reb_output_check(r, 10.*2.*M_PI)){
reb_output_timing(r, 0);
}
}


This example is located in the directory examples/mergers