def simulation(par):
saturn_a, saturn_e = par
rebound.reset()
rebound.integrator = "whfast-nocor"
rebound.dt = 5.
# These parameters are only approximately those of Jupiter and Saturn.
rebound.add(m=1.)
rebound.add(m=0.000954, a=5.204, anom=0.600, omega=0.257, e=0.048)
rebound.add(m=0.000285, a=saturn_a, anom=0.871, omega=1.616, e=saturn_e)
rebound.move_to_com()
rebound.init_megno(1e-16)
rebound.integrate(5e2*2.*np.pi) # integrator for 500 years
return [rebound.calculate_megno(),1./(rebound.calculat_lyapunov()*2.*np.pi)] # returns MEGNO and Lypunov timescale in years
def simulation(par):
saturn_a, saturn_e = par
rebound.reset()
rebound.set_min_dt(0.1)
# These parameters are only approximately those of Jupiter and Saturn.
sun = rebound.Particle(m=1.)
rebound.particle_add(sun)
jupiter = rebound.particle_add(primary=sun,m=0.000954, a=5.204, anom=0.600, omega=0.257, e=0.048)
saturn = rebound.particle_add(primary=sun,m=0.000285, a=saturn_a, anom=0.871, omega=1.616, e=saturn_e)
rebound.move_to_center_of_momentum()
rebound.megno_init(1e-16)
rebound.integrate(1e4*2.*np.pi)
return [rebound.get_megno(),1./(rebound.get_lyapunov()*2.*np.pi)] # returns MEGNO and Lypunov timescale in years
def Destab(tmax,VarOut,Nout,sim):
dt = tmax/(Nout-1.)
OrbOut = VarOut[0]
CoordOut = VarOut[1]
step = 0
a0 = np.zeros(cfg.NumPlanet)
for i in range(cfg.NumPlanet):
a0[i] = sim.calculate_orbits()[i].a
a = a0
aHigh = 1.2*a0
aLow = 0.8*a0
Time = 0
print '\nTime ellapsed:'
while CheckSMA(a,aHigh,aLow)==True and Time<tmax:
if step%(Nout/10) == 1:
print '\t'+str(Time)+' yr'
Time = sim.t
cfg.times.append(Time)
for j in range(cfg.NumPlanet):
Orbits = sim.calculate_orbits()
a[j] = Orbits[j].a
for OrbVar in OrbOut:
getattr(cfg,OrbVar)[j].append(getattr(sim.Orbits[j],OrbVar))
for CoordVar in CoordOut:
getattr(cfg,CoordVar)[j].append(getattr(cfg.ps[j+1],CoordVar))
rebound.integrate(Time+dt)
step += 1
print Time
def simulation(par):
saturn_a, saturn_e = par
rebound.reset()
rebound.integrator = "whfast-nocor"
rebound.min_dt = 5.
rebound.dt = 1.
# These parameters are only approximately those of Jupiter and Saturn.
sun = rebound.Particle(m=1.)
rebound.add(sun)
jupiter = rebound.add(primary=sun,m=0.000954, a=5.204, anom=0.600, omega=0.257, e=0.048)
saturn = rebound.add(primary=sun,m=0.000285, a=saturn_a, anom=0.871, omega=1.616, e=saturn_e)
rebound.move_to_com()
rebound.init_megno(1e-16)
rebound.integrate(1e3*2.*np.pi)
return [rebound.calculate_megno(),1./(rebound.calculate_lyapunov()*2.*np.pi)] # returns MEGNO and Lypunov timescale in years
def simulation(integrator):
print("Running "+integrator)
with open(integrator+".txt","w") as f:
rebound.reset()
rebound.set_integrator(integrator)
rebound.set_dt(0.2)
rebound.add_particle(m=1.)
rebound.add_particle(m=0.01, a=1,e=0.1)
rebound.add_particle(m=0.01, a=2.)
rebound.move_to_center_of_momentum()
rebound.init_megno(1e-10)
particles = rebound.get_particles()
times = np.logspace(2,5,num=1000)
for t in times:
rebound.integrate(t,0)
print("%e %e %e %e %e %e %e %e\n" %(rebound.get_t(), rebound.get_megno(), particles[0].x, particles[1].x, particles[2].x, particles[3].x, particles[4].x, particles[5].x),file=f)
def simulation(integrator):
print("Running "+integrator)
with open(integrator+".txt","w") as f:
rebound.reset()
rebound.integrator = integrator
rebound.dt = 0.2
rebound.add(m=1.)
rebound.add(m=0.01, a=1,e=0.1)
rebound.add(m=0.01, a=2.)
rebound.move_to_com()
rebound.init_megno(1e-10)
particles = rebound.particles
times = np.logspace(2,5,num=1000)
for t in times:
rebound.integrate(t,0)
print("%e %e %e %e %e %e %e %e\n" %(rebound.t, rebound.calculate_megno(), particles[0].x, particles[1].x, particles[2].x, particles[3].x, particles[4].x, particles[5].x),file=f)
def simulation(par):
anom, dt, e, integrator = par
e = 1.-pow(10.,e)
dt = pow(10.,dt)*torb
rebound.reset()
rebound.set_integrator(integrator)
rebound.set_force_is_velocitydependent(0)
rebound.set_dt(dt)
rebound.add_particle(m=1.)
rebound.add_particle(m=0., x=(1.-e), vy=np.sqrt((1.+e)/(1.-e)))
particles = rebound.get_particles()
Ei = -1./np.sqrt(particles[1].x*particles[1].x+particles[1].y*particles[1].y+particles[1].z*particles[1].z) + 0.5 * (particles[1].vx*particles[1].vx+particles[1].vy*particles[1].vy+particles[1].vz*particles[1].vz)
rebound.integrate(tmax,exactFinishTime=0,keepSynchronized=1)
Ef = -1./np.sqrt(particles[1].x*particles[1].x+particles[1].y*particles[1].y+particles[1].z*particles[1].z) + 0.5 * (particles[1].vx*particles[1].vx+particles[1].vy*particles[1].vy+particles[1].vz*particles[1].vz)
return [float(rebound.get_iter())/rebound.get_t()*dt, np.fabs((Ef-Ei)/Ei)+1e-16, rebound.get_timing()/rebound.get_t()*dt*1e6/2., (Ef-Ei)/Ei]
def simulation(par):
anom, dt, e, integrator = par
e = 1.-pow(10.,e)
dt = pow(10.,dt)*torb
rebound.reset()
rebound.integrator = integrator
rebound.force_is_velocitydependent = 0
rebound.dt = dt
rebound.add(m=1.)
rebound.add(m=0., x=(1.-e), vy=np.sqrt((1.+e)/(1.-e)))
particles = rebound.particles
Ei = -1./np.sqrt(particles[1].x*particles[1].x+particles[1].y*particles[1].y+particles[1].z*particles[1].z) + 0.5 * (particles[1].vx*particles[1].vx+particles[1].vy*particles[1].vy+particles[1].vz*particles[1].vz)
rebound.integrate(tmax,exactFinishTime=0,keepSynchronized=1)
Ef = -1./np.sqrt(particles[1].x*particles[1].x+particles[1].y*particles[1].y+particles[1].z*particles[1].z) + 0.5 * (particles[1].vx*particles[1].vx+particles[1].vy*particles[1].vy+particles[1].vz*particles[1].vz)
return [float(rebound.iter)/rebound.t*dt, np.fabs((Ef-Ei)/Ei)+1e-16, rebound.timing/rebound.t*dt*1e6/2., (Ef-Ei)/Ei]
def CloseEnc(VarOut,Noutputs):
OrbOut = VarOut[0]
CoordOut = VarOut[1]
# Initializes a counter for the number of steps
step = 0
# Runs through the times
try:
for i,time in enumerate(cfg.times):
#Updates the counter
step += 1
# Prints an update to screen on how far along integration is.
if step%(Noutputs/10) == 1:
print time
# Integrate from rebound.t (previous time) to the new time
rebound.integrate(time,minD=0.001)
# Writes the orbital elements and coordinates to cfg
for j in range(cfg.NumPlanet):
com = rebound.calculate_com(j)
for OrbVar in OrbOut:
getattr(cfg,
OrbVar)[j][i] = getattr(cfg.ps[j+1].calculate_orbit(),OrbVar)
for CoordVar in CoordOut:
getattr(cfg,
CoordVar)[j][i] = getattr(cfg.ps[j+1],CoordVar)
if cfg.ps[1].x == 'nan':
print 'Not a number'
sys.exit()
except rebound.CloseEncounter as e:
print "Close encounter detected at t=%f, between particles %d and %d." % (rebound.t, e.id1, e.id2)
def simulation(par):
S, dt,e0 = par
rebound.reset()
rebound.set_integrator("wh")
#rebound.set_integrator("whfast")
rebound.set_dt(dt)
rebound.particle_add(m=1.)
rebound.particle_add(m=0.,a=1.,e=e0)
#rebound.move_to_center_of_momentum()
#rebound.megno_init(1.e-16)
particles = rebound.particles_get()
def starkforce(): # need to put inside simulation(par) to have access to S and particles
particles[1].ax += -S
rebound.set_additional_forces(starkforce)
rebound.integrate(50000.*np.pi)
return [rebound.get_megno(), rebound.get_t()]
def simulation(par):
import rebound
integrator, dt, run = par
rebound.reset()
k = 0.01720209895
G = k*k
rebound.G = G
rebound.dt = dt
if integrator == "whfast-nocor":
integrator = "whfast"
else:
rebound.integrator_whfast_corrector = 11
rebound.integrator = integrator
rebound.force_is_velocitydependent = 0
rebound.add(m=1.00000597682, x=-4.06428567034226e-3, y=-6.08813756435987e-3, z=-1.66162304225834e-6, vx=+6.69048890636161e-6, vy=-6.33922479583593e-6, vz=-3.13202145590767e-9) # Sun
rebound.add(m=1./1407.355, x=+3.40546614227466e+0, y=+3.62978190075864e+0, z=+3.42386261766577e-2, vx=-5.59797969310664e-3, vy=+5.51815399480116e-3, vz=-2.66711392865591e-6) # Jupiter
rebound.add(m=1./3501.6, x=+6.60801554403466e+0, y=+6.38084674585064e+0, z=-1.36145963724542e-1, vx=-4.17354020307064e-3, vy=+3.99723751748116e-3, vz=+1.67206320571441e-5) # Saturn
rebound.add(m=1./22869., x=+1.11636331405597e+1, y=+1.60373479057256e+1, z=+3.61783279369958e-1, vx=-3.25884806151064e-3, vy=+2.06438412905916e-3, vz=-2.17699042180559e-5) # Uranus
rebound.add(m=1./19314., x=-3.01777243405203e+1, y=+1.91155314998064e+0, z=-1.53887595621042e-1, vx=-2.17471785045538e-4, vy=-3.11361111025884e-3, vz=+3.58344705491441e-5) # Neptune
N = rebound.N
particles = rebound.particles
np.random.seed(run)
for i in xrange(N):
particles[i].m *= 1.+1e-3*np.random.rand()
particles[i].x *= 1.+1e-3*np.random.rand()
particles[i].y *= 1.+1e-3*np.random.rand()
particles[i].z *= 1.+1e-3*np.random.rand()
particles[i].vx *= 1.+1e-3*np.random.rand()
particles[i].vy *= 1.+1e-3*np.random.rand()
particles[i].vz *= 1.+1e-3*np.random.rand()
def move_to_heliocentric():
particles[0].x = 0.
particles[0].y = 0.
particles[0].z = 0.
particles[0].vx = 0.
particles[0].vy = 0.
particles[0].vz = 0.
def energy():
com_vx = 0.
com_vy = 0.
com_vz = 0.
if integrator=="wh" or integrator=="mercury" or integrator[0:7]=="swifter":
mtot = 0.
for i in xrange(0,N):
com_vx += particles[i].vx*particles[i].m
com_vy += particles[i].vy*particles[i].m
com_vz += particles[i].vz*particles[i].m
mtot += particles[i].m
com_vx /= mtot
com_vy /= mtot
com_vz /= mtot
E_kin = 0.
E_pot = 0.
for i in xrange(N):
dvx = particles[i].vx - com_vx
dvy = particles[i].vy - com_vy
dvz = particles[i].vz - com_vz
E_kin += 0.5*particles[i].m*(dvx*dvx + dvy*dvy + dvz*dvz)
for j in xrange(i+1,N):
dx = particles[i].x-particles[j].x
dy = particles[i].y-particles[j].y
dz = particles[i].z-particles[j].z
r2 = dx*dx + dy*dy + dz*dz
E_pot -= G*particles[i].m*particles[j].m/np.sqrt(r2)
return E_kin+E_pot
if integrator=="wh" or integrator=="mercury" or integrator[0:7]=="swifter":
move_to_heliocentric()
else:
rebound.move_to_com()
ei = energy()
runtime = 0.
rebound.integrate(tmax,exact_finish_time=0)
ef = energy()
e = np.fabs((ei-ef)/ei)+1.1e-16
runtime += rebound.timing
integrator, dt, run = par
print integrator.ljust(13) + " %9.5fs"%(runtime) + "\t Error: %e" %( e)
return [runtime, e]
# Add particles
# We work in units where G=1.
rebound.add(m=1. ) # Test particle
rebound.add(m=1e-3,x=1.,vy=1. ) # Planet
# Move particles so that the center of mass is (and stays) at the origin
rebound.move_to_com()
# You can provide a function, written in python to REBOUND.
# This function gets called every time the forces are evaluated.
# Simple add any any additional (non-gravitational) forces to the
# particle accelerations. Here, we add a simple drag force. This
# will make the planet spiral into the star.
ps = rebound.particles
def dragforce():
dragcoefficient = 1e-2
for p in ps:
p.ax += -dragcoefficient * p.vx
p.ay += -dragcoefficient * p.vy
p.az += -dragcoefficient * p.vz
# Tell rebound which function to call
rebound.additional_forces = dragforce
# Integrate until t=100 (roughly 16 orbits at 1 AU)
rebound.integrate(100.)
# Output something at the end (the planet will be at ~0.1 AU)
for p in ps:
print(p.x, p.y, p.z)
def simulation(par):
integrator, run, trial = par
rebound.reset()
k = 0.01720209895
Gfac = 1./k
rebound.set_dt(dt)
rebound.set_integrator(integrator)
rebound.set_force_is_velocitydependent(0)
massfac = 1.
rebound.add_particle(m=1.00000597682, x=-4.06428567034226e-3, y=-6.08813756435987e-3, z=-1.66162304225834e-6, vx=+6.69048890636161e-6*Gfac, vy=-6.33922479583593e-6*Gfac, vz=-3.13202145590767e-9*Gfac) # Sun
rebound.add_particle(m=massfac/1407.355, x=+3.40546614227466e+0, y=+3.62978190075864e+0, z=+3.42386261766577e-2, vx=-5.59797969310664e-3*Gfac, vy=+5.51815399480116e-3*Gfac, vz=-2.66711392865591e-6*Gfac) # Jupiter
rebound.add_particle(m=massfac/3501.6, x=+6.60801554403466e+0, y=+6.38084674585064e+0, z=-1.36145963724542e-1, vx=-4.17354020307064e-3*Gfac, vy=+3.99723751748116e-3*Gfac, vz=+1.67206320571441e-5*Gfac) # Saturn
rebound.add_particle(m=massfac/22869., x=+1.11636331405597e+1, y=+1.60373479057256e+1, z=+3.61783279369958e-1, vx=-3.25884806151064e-3*Gfac, vy=+2.06438412905916e-3*Gfac, vz=-2.17699042180559e-5*Gfac) # Uranus
rebound.add_particle(m=massfac/19314., x=-3.01777243405203e+1, y=+1.91155314998064e+0, z=-1.53887595621042e-1, vx=-2.17471785045538e-4*Gfac, vy=-3.11361111025884e-3*Gfac, vz=+3.58344705491441e-5*Gfac) # Neptune
N = rebound.get_N()
particles = rebound.get_particles()
np.random.seed(run)
for i in xrange(N):
particles[i].m *= 1.+1e-3*np.random.rand()
particles[i].x *= 1.+1e-3*np.random.rand()
particles[i].y *= 1.+1e-3*np.random.rand()
particles[i].z *= 1.+1e-3*np.random.rand()
particles[i].vx *= 1.+1e-3*np.random.rand()
particles[i].vy *= 1.+1e-3*np.random.rand()
particles[i].vz *= 1.+1e-3*np.random.rand()
def move_to_heliocentric():
particles = rebound.get_particles()
particles[0].x = 0.
particles[0].y = 0.
particles[0].z = 0.
particles[0].vx = 0.
particles[0].vy = 0.
particles[0].vz = 0.
def energy():
particles = rebound.get_particles()
com_vx = 0.
com_vy = 0.
com_vz = 0.
if integrator=="wh" or integrator=="mercury" or integrator[0:7]=="swifter":
mtot = 0.
for i in xrange(0,N):
com_vx += particles[i].vx*particles[i].m
com_vy += particles[i].vy*particles[i].m
com_vz += particles[i].vz*particles[i].m
mtot += particles[i].m
com_vx /= mtot
com_vy /= mtot
com_vz /= mtot
E_kin = 0.
E_pot = 0.
for i in xrange(N):
dvx = particles[i].vx - com_vx
dvy = particles[i].vy - com_vy
dvz = particles[i].vz - com_vz
E_kin += 0.5*particles[i].m*(dvx*dvx + dvy*dvy + dvz*dvz)
for j in xrange(i+1,N):
dx = particles[i].x-particles[j].x
dy = particles[i].y-particles[j].y
dz = particles[i].z-particles[j].z
r2 = dx*dx + dy*dy + dz*dz
E_pot -= particles[i].m*particles[j].m/np.sqrt(r2)
return E_kin+E_pot
times = np.logspace(np.log10(orbit),np.log10(tmax),Ngrid)
if integrator=="wh" or integrator=="mercury" or integrator[0:7]=="swifter":
move_to_heliocentric()
else:
rebound.move_to_center_of_momentum()
ei = energy()
es = []
runtime = 0.
for t in times:
rebound.integrate(t,exactFinishTime=0,keepSynchronized=0)
ef = energy()
e = np.fabs((ei-ef)/ei)+1.1e-16
es.append(e)
runtime += rebound.get_timing()
integrator, run, trial = par
print integrator.ljust(13) + " %9.5fs"%(runtime) + "\t Error: %e" %( e)
es = np.array(es)
return [times, es]
rebound.save("cache.bin")
rebound.set_integrator("whfast")
rebound.set_dt(0.01)
rebound.status()
import numpy as np
Nout = 1000
times = np.linspace(0,16.*np.pi,Nout) # 8 years
N = rebound.get_N()
x = np.zeros((N,Nout))
y = np.zeros((N,Nout))
p = rebound.get_particles()
for ti,t in enumerate(times):
rebound.integrate(t)
for i in xrange(0,N):
x[i][ti] = p[i].x
y[i][ti] = p[i].y
import matplotlib; matplotlib.use("pdf")
import matplotlib.pyplot as plt
fig = plt.figure(figsize=(11,5))
def plot(zoom):
ax.set_xlim([-zoom,zoom])
ax.set_ylim([-zoom,zoom])
ax.set_xlabel("x [AU]")
ax.set_ylabel("y [AU]")
for i in xrange(0,N):
tmax = 1.e4 # years
rebound.add(m=1.)
rebound.add(m=1e-6,a=1.,e=0.5)
#rebound.add(m=1e-6,a=2.,e=0.5)
rebound.move_to_com() # Moves to the center of momentum frame
rebound.additional_forces = reboundxf.forces()
reboundxf.set_e_damping([0.,tmax/10.])#,tmax])
reboundxf.set_migration([0.,0.])#,tmax])
Nout = 1000
e1,e2,a1,a2 = np.zeros(Nout), np.zeros(Nout), np.zeros(Nout), np.zeros(Nout)
times = np.linspace(0.,tmax,Nout)
for i,time in enumerate(times):
rebound.integrate(time)
orbits = rebound.calculate_orbits()
e1[i] = orbits[0].e
#e2[i] = orbits[1].e
a1[i] = orbits[0].a
#a2[i] = orbits[1].a
import matplotlib.pyplot as plt
fig = plt.figure(figsize=(15,5))
ax = plt.subplot(111)
ax.set_yscale('log')
plt.plot(times,e1)
#plt.plot(times,e2)
fig = plt.figure(figsize=(15,5))
ax = plt.subplot(111)
def simulation(par):
integrator, run, trial = par
rebound.reset()
k = 0.01720209895
Gfac = 1./k
rebound.dt = dt
rebound.integrator = integrator
rebound.force_is_velocitydependent = 0
massfac = 1.
rebound.add(m=1.00000597682, x=-4.06428567034226e-3, y=-6.08813756435987e-3, z=-1.66162304225834e-6, vx=+6.69048890636161e-6*Gfac, vy=-6.33922479583593e-6*Gfac, vz=-3.13202145590767e-9*Gfac) # Sun
rebound.add(m=massfac/1407.355, x=+3.40546614227466e+0, y=+3.62978190075864e+0, z=+3.42386261766577e-2, vx=-5.59797969310664e-3*Gfac, vy=+5.51815399480116e-3*Gfac, vz=-2.66711392865591e-6*Gfac) # Jupiter
rebound.add(m=massfac/3501.6, x=+6.60801554403466e+0, y=+6.38084674585064e+0, z=-1.36145963724542e-1, vx=-4.17354020307064e-3*Gfac, vy=+3.99723751748116e-3*Gfac, vz=+1.67206320571441e-5*Gfac) # Saturn
rebound.add(m=massfac/22869., x=+1.11636331405597e+1, y=+1.60373479057256e+1, z=+3.61783279369958e-1, vx=-3.25884806151064e-3*Gfac, vy=+2.06438412905916e-3*Gfac, vz=-2.17699042180559e-5*Gfac) # Uranus
rebound.add(m=massfac/19314., x=-3.01777243405203e+1, y=+1.91155314998064e+0, z=-1.53887595621042e-1, vx=-2.17471785045538e-4*Gfac, vy=-3.11361111025884e-3*Gfac, vz=+3.58344705491441e-5*Gfac) # Neptune
N = rebound.N
particles = rebound.particles
np.random.seed(run)
for p in particles:
p.m *= 1.+1e-3*np.random.rand()
p.x *= 1.+1e-3*np.random.rand()
p.y *= 1.+1e-3*np.random.rand()
p.z *= 1.+1e-3*np.random.rand()
p.vx *= 1.+1e-3*np.random.rand()
p.vy *= 1.+1e-3*np.random.rand()
p.vz *= 1.+1e-3*np.random.rand()
def move_to_heliocentric():
particles[0].x = 0.
particles[0].y = 0.
particles[0].z = 0.
particles[0].vx = 0.
particles[0].vy = 0.
particles[0].vz = 0.
def energy():
com_vx = 0.
com_vy = 0.
com_vz = 0.
if integrator=="wh" or integrator=="mercury" or integrator[0:7]=="swifter":
mtot = 0.
for p in particles:
com_vx += p.vx*p.m
com_vy += p.vy*p.m
com_vz += p.vz*p.m
mtot += p.m
com_vx /= mtot
com_vy /= mtot
com_vz /= mtot
E_kin = 0.
E_pot = 0.
for i in xrange(N):
dvx = particles[i].vx - com_vx
dvy = particles[i].vy - com_vy
dvz = particles[i].vz - com_vz
E_kin += 0.5*particles[i].m*(dvx*dvx + dvy*dvy + dvz*dvz)
for j in xrange(i+1,N):
dx = particles[i].x-particles[j].x
dy = particles[i].y-particles[j].y
dz = particles[i].z-particles[j].z
r2 = dx*dx + dy*dy + dz*dz
E_pot -= particles[i].m*particles[j].m/np.sqrt(r2)
return E_kin+E_pot
times = np.logspace(np.log10(orbit),np.log10(tmax),Ngrid)
if integrator=="wh" or integrator=="mercury" or integrator[0:7]=="swifter":
move_to_heliocentric()
else:
rebound.move_to_com()
ei = energy()
es = []
runtime = 0.
for t in times:
rebound.integrate(t,exactFinishTime=0,keepSynchronized=0)
ef = energy()
e = np.fabs((ei-ef)/ei)+1.1e-16
es.append(e)
runtime += rebound.timing
integrator, run, trial = par
print integrator.ljust(13) + " %9.5fs"%(runtime) + "\t Error: %e" %( e)
es = np.array(es)
return [times, es]
from rebound import Particle
# Set variables (defaults are G=1, t=0, dt=0.01)
# rebound.set_G(1.)
# rebound.set_t(0.)
# rebound.set_dt(0.01)
# Add particles
rebound.particle_add(Particle(m=1.0)) # Star
rebound.particle_add(Particle(m=1e-3, x=1.0, vy=1.0)) # Planet
# Move particles so that the center of mass is (and stays) at the origin
rebound.move_to_center_of_momentum()
# Integrate until t=100 (roughly 16 orbits)
rebound.integrate(100.0)
# Modify particles
# As an example, we are reverting the velocities
particles = rebound.particles_get()
for i in range(rebound.get_N()):
particles[i].vx *= -1.0
particles[i].vy *= -1.0
particles[i].vz *= -1.0
# Integrate another 100 time units, until t=200
rebound.integrate(200.0)
# Get particles back and print positions
# Since we're integrating forward and then backward we end up with the
# particles exactly where they started out from (note that we moved to the
rebound.add(m=1e-3, x=1., vy=1.) # Planet
# Move particles so that the center of mass is (and stays) at the origin
rebound.move_to_com()
# You can provide a function, written in python to REBOUND.
# This function gets called every time the forces are evaluated.
# Simple add any any additional (non-gravitational) forces to the
# particle accelerations. Here, we add a simple drag force. This
# will make the planet spiral into the star.
ps = rebound.particles
def dragforce():
dragcoefficient = 1e-2
for p in ps:
p.ax += -dragcoefficient * p.vx
p.ay += -dragcoefficient * p.vy
p.az += -dragcoefficient * p.vz
# Tell rebound which function to call
rebound.additional_forces = dragforce
# Integrate until t=100 (roughly 16 orbits at 1 AU)
rebound.integrate(100.)
# Output something at the end (the planet will be at ~0.1 AU)
for p in ps:
print(p.x, p.y, p.z)