import os.path
from amuse.test.amusetest import get_path_to_results
try:
from matplotlib import pyplot
HAS_MATPLOTLIB = True
from amuse.plot import plot, semilogy, xlabel, ylabel, loglog
except ImportError:
HAS_MATPLOTLIB = False
from amuse.units import units
from amuse.units import constants
from amuse.units.generic_unit_converter import ConvertBetweenGenericAndSiUnits
from amuse.support.exceptions import AmuseException
from amuse.community.mesa.interface import MESA
from amuse.community.gadget2.interface import Gadget2
from amuse.community.fi.interface import Fi
from amuse.ext.star_to_sph import convert_stellar_model_to_SPH
import numpy
from amuse.datamodel import Particles
from amuse.datamodel import ParticlesSuperset
from amuse.datamodel import Grid
def head_on_stellar_merger(
masses = [0.3, 3.0] | units.MSun,
star_age = 310.0 | units.Myr,
initial_separation = 4.0 | units.RSun,
angle = numpy.pi / 3,
initial_speed = 3000.0 | units.km / units.s,
initial_speed_perpendicular = 30.0 | units.km / units.s,
number_of_sph_particles = 50000,
t_end = 1.0e4 | units.s,
sph_code = Fi,
):
"""
masses: Mass of the two stars
star_age: Initial age of the stars
number_of_sph_particles: Total number of particles of both stars, divided according to their masses
t_end: (Physical, not computational) duration of the hydrodynamics simulation
sph_code: Code to use for the hydrodynamics simulation
"""
# Convert some of the input parameters to string, for use in output file names:
n_string = "n" + ("%1.0e"%(number_of_sph_particles)).replace("+0","").replace("+","")
t_end_string = "t" + ("%1.0e"%(t_end.value_in(units.s))).replace("+0","").replace("+","")
base_output_file_name = os.path.join(get_path_to_results(), "stellar_merger_"+n_string+"_"+t_end_string)
stars = Particles(2)
stars.mass = masses
try:
stellar_evolution = MESA()
stellar_evolution.initialize_code()
except:
print "MESA was not built. Returning."
return
stellar_evolution.commit_parameters()
stellar_evolution.particles.add_particles(stars)
stellar_evolution.commit_particles()
print "Evolving stars with MESA..."
stellar_evolution.evolve_model(star_age)
number_of_sph_particles_1 = int(round(number_of_sph_particles *
(stellar_evolution.particles[0].mass / stellar_evolution.particles.mass.sum())))
number_of_sph_particles_2 = number_of_sph_particles - number_of_sph_particles_1
print "Creating initial conditions from a MESA stellar evolution model:"
print stellar_evolution.particles[0].mass, "star consisting of", number_of_sph_particles_1, "particles."
sph_particles_1 = convert_stellar_model_to_SPH(
stellar_evolution.particles[0],
number_of_sph_particles_1,
seed=12345
).gas_particles
print stellar_evolution.particles[1].mass, "star consisting of", number_of_sph_particles_2, "particles."
sph_particles_2 = convert_stellar_model_to_SPH(
stellar_evolution.particles[1],
number_of_sph_particles_2
).gas_particles
initial_separation += stellar_evolution.particles.radius.sum()
sph_particles_2.x += numpy.cos(angle) * initial_separation
sph_particles_2.y += numpy.sin(angle) * initial_separation
sph_particles_1.vx += numpy.cos(angle) * initial_speed - numpy.sin(angle) * initial_speed_perpendicular
sph_particles_1.vy += numpy.cos(angle) * initial_speed_perpendicular + numpy.sin(angle) * initial_speed
view = [-0.5, 0.5, -0.5, 0.5] * (initial_separation + stellar_evolution.particles.radius.sum())
stellar_evolution.stop()
all_sph_particles = ParticlesSuperset([sph_particles_1, sph_particles_2])
all_sph_particles.move_to_center()
unit_converter = ConvertBetweenGenericAndSiUnits(1.0 | units.RSun, constants.G, t_end)
hydro_legacy_code = sph_code(unit_converter)
n_steps = 100
hydro_legacy_code.parameters.n_smooth = 96
try:
hydro_legacy_code.parameters.timestep = t_end / n_steps
except Exception as exc:
if not "parameter is read-only" in str(exc): raise
hydro_legacy_code.gas_particles.add_particles(all_sph_particles)
print "Evolving to t =", t_end, " (using", sph_code.__name__, "SPH code)."
for time, i_step in [(i*t_end/n_steps, i) for i in range(1, n_steps+1)]:
hydro_legacy_code.evolve_model(time)
if not i_step % 4:
hydro_plot(
view,
hydro_legacy_code,
(300, 300),
base_output_file_name + "_hydro_image{0:=03}.png".format(i_step)
)
hydro_legacy_code.stop()
print "All done!\n"
def hydro_plot(view, hydro_code, image_size, figname):
"""
view: the (physical) region to plot [xmin, xmax, ymin, ymax]
hydro_code: hydrodynamics code in which the gas to be plotted is defined
image_size: size of the output image in pixels (x, y)
"""
shape = (image_size[0], image_size[1], 1)
size = image_size[0] * image_size[1]
axis_lengths = [0.0, 0.0, 0.0] | units.m
axis_lengths[0] = view[1] - view[0]
axis_lengths[1] = view[3] - view[2]
grid = Grid.create(shape, axis_lengths)
grid.x += view[0]
grid.y += view[2]
speed = grid.z.reshape(size) * (0 | 1/units.s)
rho, rhovx, rhovy, rhovz, rhoe = hydro_code.get_hydro_state_at_point(grid.x.reshape(size),
grid.y.reshape(size), grid.z.reshape(size), speed, speed, speed)
min_v = 800.0 | units.km / units.s
max_v = 3000.0 | units.km / units.s
min_rho = 3.0e-4 | units.g / units.cm**3
max_rho = 0.1 | units.g / units.cm**3
min_E = 1.0e11 | units.J / units.kg
max_E = 1.0e13 | units.J / units.kg
v_sqr = (rhovx**2 + rhovy**2 + rhovz**2) / rho**2
E = rhoe / rho
log_v = numpy.log((v_sqr / min_v**2)) / numpy.log((max_v**2 / min_v**2))
log_rho = numpy.log((rho / min_rho)) / numpy.log((max_rho / min_rho))
log_E = numpy.log((E / min_E)) / numpy.log((max_E / min_E))
red = numpy.minimum(numpy.ones_like(rho.number), numpy.maximum(numpy.zeros_like(rho.number), log_rho)).reshape(shape)
green = numpy.minimum(numpy.ones_like(rho.number), numpy.maximum(numpy.zeros_like(rho.number), log_v)).reshape(shape)
blue = numpy.minimum(numpy.ones_like(rho.number), numpy.maximum(numpy.zeros_like(rho.number), log_E)).reshape(shape)
alpha = numpy.minimum(numpy.ones_like(log_v), numpy.maximum(numpy.zeros_like(log_v),
numpy.log((rho / (10*min_rho))))).reshape(shape)
rgba = numpy.concatenate((red, green, blue, alpha), axis = 2)
pyplot.figure(figsize = (image_size[0]/100.0, image_size[1]/100.0), dpi = 100)
im = pyplot.figimage(rgba, origin='lower')
pyplot.savefig(figname, transparent=True, dpi = 100)
print "\nHydroplot was saved to: ", figname
pyplot.close()
if __name__ == "__main__":
print "Running the simulation that formed the basis of the christmas card of Leiden Observatory of 2010."
print
print "Details:"
print "The ornaments are the result of a smoothed particle simulation " \
"with 50000 equal mass particles of a 310 Myr star of 0.3 solar mass, " \
"which is ejected from a distance of 4 solar radii (left) " \
"with a velocity of 3000 km/s into a 3.0 solar mass star at an " \
"age of 310 Myr. The calculation was performed using the AMUSE " \
"(amusecode.org) software environment in which the stars were evolved " \
"using MESA to an age of 310 Myr before the encounter was performed " \
"using Fi. Each ornament, generated using pyplot, is a snapshot from the " \
"simulation, from top left to bottom right. The peak is created from a " \
"blend of all snapshots. The colors of the ornaments are, red: log " \
"of the density, green: log of the speed and for blue we used " \
"the log of the specific internal energy."
print
if HAS_MATPLOTLIB:
head_on_stellar_merger()
else:
print "matplotlib is not installed. Install it in the site-packages folder of your Python installation. Returning."
Keywords: python, amuse, astrophysics, matplotlib, pylab, example, codex (see how-to-search-examples)