textbook example code: molecular_cloud_collapse_with_sinks.pyΒΆ

[source code]

import numpy
from matplotlib import pyplot

from amuse.lab import *
from amuse.ext.molecular_cloud import molecular_cloud
from amuse.ext.evrard_test import body_centered_grid_unit_cube

from cooling_class import SimplifiedThermalModel, SimplifiedThermalModelEvolver
from hydrodynamics_class import Hydro

def run_molecular_cloud(N=100, Mcloud=100. | units.MSun,
                        Rcloud=1. | units.parsec):

    conv = nbody_system.nbody_to_si(Mcloud,Rcloud)
    gas=molecular_cloud(targetN=N,convert_nbody=conv,
            base_grid=body_centered_grid_unit_cube).result
    gas.name = "gas"

    rho_cloud = Mcloud/Rcloud**3
    tff = 0.5427/numpy.sqrt(constants.G*rho_cloud)
    print "Freefall timescale=", tff.in_(units.Myr)

    stars = Particles(0)
    hydro = Hydro(Fi, gas, stars)

    rho_cloud = 3.*Mcloud/(4.*numpy.pi*Rcloud**3)
    print rho_cloud

    dt = 0.02 | units.Myr
    tend= 10.0 | units.Myr
    dt_diag = 0.1 | units.Myr
    t_diag = 0 | units.Myr

    i=0
    E0 = 0.0
    time = 0.0 | units.Myr

    while time < tend:
        time += dt
        print "Evolve to time=", time.in_(units.Myr)
        Mtot = 0|units.MSun
        if len(hydro.star_particles) > 0:
            print "Mass conservation: Slocal:", time.in_(units.Myr), \
                  hydro.gas_particles.mass.sum().in_(units.MSun), \
                  hydro.star_particles.mass.sum().in_(units.MSun), \
                  "sum=", (hydro.gas_particles.mass.sum() \
                            + hydro.star_particles.mass.sum()).in_(units.MSun)
            print "Mass conservation: Shydro:", time.in_(units.Myr), \
                  hydro.code.gas_particles.mass.sum().in_(units.MSun), \
                  hydro.code.dm_particles.mass.sum().in_(units.MSun), \
                  "sum=", \
                  (hydro.code.gas_particles.mass.sum() \
                    + hydro.code.dm_particles.mass.sum()).in_(units.MSun), \
                    "S=", hydro.star_particles.mass.sum().in_(units.MSun)
            Mtot = hydro.gas_particles.mass.sum() \
                    + hydro.star_particles.mass.sum()
        else:
            print "Mass conservation: local:", time.in_(units.Myr), \
                  hydro.gas_particles.mass.sum().in_(units.MSun)
            print "Mass conservation: hydro:", time.in_(units.Myr), \
                  hydro.code.gas_particles.mass.sum().in_(units.MSun)
            Mtot = hydro.gas_particles.mass.sum()

        if Mtot < Mcloud-(1.e-5|units.MSun):
            print "Mass is not conserved:", Mtot.in_(units.MSun), \
                  Mcloud.in_(units.MSun)
            exit(-1)

        hydro.evolve_model(time)
        E = hydro.gas_particles.kinetic_energy() \
             + hydro.gas_particles.potential_energy() \
             + hydro.gas_particles.thermal_energy()
        E_th = hydro.gas_particles.thermal_energy()
        if i==0:
            E0 = E
        Eerr = (E-E0)/E0
        print 'energy=', E, 'energy_error=', Eerr, 'e_th=', E_th
        print "maximal_density:",gas.rho.max().in_(units.MSun/units.parsec**3)

        hydro.print_diagnostics()
        if time>t_diag:
            t_diag += dt_diag
            hydro.write_set_to_file(i)
            i=i+1

    hydro.stop()
    return gas

if __name__ in ("__main__","__plot__"):
    numpy.random.seed(3141)
    parts = run_molecular_cloud(10000, Mcloud=1000. | units.MSun,
                                Rcloud=3.0 | units.parsec)

Keywords: python, amuse, astrophysics, matplotlib, pylab, example, codex (see how-to-search-examples)