def relative_position_and_velocity_from_orbital_elements(
mass1, mass2, semimajor_axis, eccentricity, mean_anomaly, seed=None):
"""
Function that returns relative positions and velocity vectors or orbiters with masses
mass2 of the central body with mass mass1 in Cartesian coordinates;
for vectors of orbital elements -- semi-major axes, eccentricities, mean anomalies.
3D orientation of orbits (inclination, longitude of ascending node and argument of periapsis) are random.
(cos(incl) is uniform -1--1, longitude of ascending node and argument of periapsis are uniform 0--2pi)
Assuming mass1 is static in the center [0,0,0] m, [0,0,0] km/s (that is mass2<<mass1)
"""
position_vectors = []
velocity_vectors = []
converter = nbody_system.nbody_to_si(1 | units.MSun, 1 | units.AU)
kepler = Kepler(converter)
kepler.initialize_code()
r_vec = (0., 0., 0.) | units.AU
v_vec = (0., 0., 0.) | units.kms
# to change seed for each particle
if seed is not None:
i = 0
for m2_i, a_i, ecc_i, ma_i in zip(mass2, semimajor_axis, eccentricity,
mean_anomaly):
#print m2_i, a_i, ecc_i, ma_i
if seed is not None:
kepler.set_random(seed + i)
i = i + 1
kepler.initialize_from_elements(mass=(mass1 + m2_i),
semi=a_i,
ecc=ecc_i,
mean_anomaly=ma_i,
random_orientation=-1)
ri = kepler.get_separation_vector()
vi = kepler.get_velocity_vector()
# this is to get ~half of the orbits retrograde (that is with inclination
# of 90--180 degrees) --> velocity = -velocity
vel_vec_dir = numpy.random.random()
if (vel_vec_dir <= 0.5):
vel_orientation = 1.
else:
vel_orientation = -1.
position_vectors.append([ri[0], ri[1], ri[2]])
velocity_vectors.append([
vel_orientation * vi[0], vel_orientation * vi[1],
vel_orientation * vi[2]
])
kepler.stop()
return position_vectors, velocity_vectors
def relative_position_and_velocity_from_orbital_elements(mass1,
mass2,
semimajor_axis,
eccentricity,
mean_anomaly,
seed=None):
"""
Function that returns relative positions and velocity vectors or orbiters with masses
mass2 of the central body with mass mass1 in Cartesian coordinates;
for vectors of orbital elements -- semi-major axes, eccentricities, mean anomalies.
3D orientation of orbits (inclination, longitude of ascending node and argument of periapsis) are random.
(cos(incl) is uniform -1--1, longitude of ascending node and argument of periapsis are uniform 0--2pi)
Assuming mass1 is static in the center [0,0,0] m, [0,0,0] km/s (that is mass2<<mass1)
"""
position_vectors = []
velocity_vectors = []
converter = nbody_system.nbody_to_si(1|units.MSun,1|units.AU)
kepler = Kepler(converter)
kepler.initialize_code()
r_vec = (0.,0.,0.) | units.AU
v_vec = (0.,0.,0.) | units.kms
# to change seed for each particle
if seed is not None:
i=0
for m2_i, a_i, ecc_i, ma_i in zip(mass2, semimajor_axis, eccentricity, mean_anomaly):
#print m2_i, a_i, ecc_i, ma_i
if seed is not None:
kepler.set_random(seed+i)
i=i+1
kepler.initialize_from_elements(mass=(mass1+m2_i),semi=a_i,ecc=ecc_i,mean_anomaly=ma_i,random_orientation=-1)
ri = kepler.get_separation_vector()
vi = kepler.get_velocity_vector()
# this is to get ~half of the orbits retrograde (that is with inclination
# of 90--180 degrees) --> velocity = -velocity
vel_vec_dir = numpy.random.random()
if (vel_vec_dir<=0.5):
vel_orientation = 1.
else:
vel_orientation = -1.
position_vectors.append([ri[0], ri[1], ri[2]])
velocity_vectors.append([vel_orientation*vi[0], vel_orientation*vi[1], vel_orientation*vi[2]])
kepler.stop()
return position_vectors, velocity_vectors
def run_kepler(mass, semi, ecc, time):
kep = Kepler(redirection='none')
kep.initialize_code()
kep.set_longitudinal_unit_vector(1.0, 1.0,
0.0)
kep.initialize_from_elements(mass, semi, ecc)
a,e = kep.get_elements()
p = kep.get_periastron()
print "elements:", a, e, p
kep.transform_to_time(time)
x,y,z = kep.get_separation_vector()
print "separation:", x,y,z
x,y,z = kep.get_longitudinal_unit_vector()
print "longitudinal:", x,y,z
pos = [1, 0, 0] | nbody_system.length
vel = [0, 0.5, 0] | nbody_system.speed
kep.initialize_from_dyn(mass, pos[0], pos[1], pos[2],
vel[0], vel[1], vel[2])
a,e = kep.get_elements()
p = kep.get_periastron()
print "elements:", a, e, p
kep.transform_to_time(time)
x,y,z = kep.get_separation_vector()
print "separation:", x,y,z
x,y,z = kep.get_velocity_vector()
print "velocity:", x,y,z
x,y,z = kep.get_longitudinal_unit_vector()
print "longitudinal:", x,y,z
kep.set_random(42)
kep.make_binary_scattering(0.5 | nbody_system.mass,
0.5,
0.5 | nbody_system.mass,
0.0 | nbody_system.speed,
0.0 | nbody_system.length,
1.e-6,
0)
kep.stop()
assert is_mpd_running()
# Instantiate workers once only and pass to scatter3 as arguments.
gravity = SmallN(redirection="none")
#gravity = SmallN(redirection = "none", debugger="valgrind") # search for
# memory leaks
gravity.initialize_code()
gravity.parameters.set_defaults()
gravity.parameters.timestep_parameter = accuracy_parameter
gravity.parameters.unperturbed_threshold = gamma
kep = Kepler(redirection="none") #, debugger="gdb")
kep.initialize_code()
kep.set_random(random_seed) # ** Note potential conflict between C++
# ** and Python random generators.
# Timing:
cpu = numpy.zeros(4)
for i in range(nscatter):
final, dcpu = scatter3(init, kep, gravity, gamma, delta_t, t_end)
cpu += dcpu
print ''
if final.is_over == 0:
print 'interaction is not over'
else:
random_seed = numpy.random.randint(1, pow(2,31)-1)
numpy.random.seed(random_seed)
print "random seed =", random_seed, numpy.random.random()
#-----------------------------------------------------------------
assert is_mpd_running()
# Instantiate worker modules once only and pass them to scatter32
# as arguments.
# Kepler manages two-body dynamics.
kep = Kepler(redirection = "none") #, debugger="gdb")
kep.initialize_code()
kep.set_random(random_seed) # ** Note potential conflict between C++
# ** and Python random generators.
# Gravity manages the N-body integration.
gravity = SmallN(redirection = "none")
gravity.initialize_code()
gravity.parameters.set_defaults()
gravity.parameters.timestep_parameter = accuracy_parameter
gravity.parameters.unperturbed_threshold = gamma
# Treecheck determines the structure of the 3-body system.
# Treecheck = gravity is OK.
treecheck = SmallN(redirection = "none")
treecheck.initialize_code()
