Added Chambers 2013 initial conditions generator

examples/Chambers2013/.gitignore

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+*
+!.gitignore
+!init_cond.py

examples/Chambers2013/init_cond.py

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+#!/usr/bin/env python3
+import swiftest
+import numpy as np
+from numpy.random import default_rng
+
+# Initialize simulation object
+sim = swiftest.Simulation(simdir="fragglesim")
+
+sim.set_parameter(compute_conservation_values=True,  rotation=True, init_cond_format="EL",collision_model="fraggle",encounter_save="none")
+
+# Add bodies described in Chambers (2013) Sec. 2.1, with the uniform spatial distribution and two bodies sizes (big and small)
+Nb = 14
+Ns = 140
+Mb = 2.8e-7 * 14 / Nb
+Ms = 2.8e-8 * 140 / Ns
+dens = 3000.0 / (sim.param['MU2KG'] / sim.param['DU2M']**3)
+Rb = (3 * Mb / (4 * np.pi * dens) )**(1.0 / 3.0)
+Rs = (3 * Ms / (4 * np.pi * dens) )**(1.0 / 3.0)
+mtiny = 1e-2 * Ms
+mininum_fragment_mass = 1e-4 * Ms
+rng = default_rng(seed=880334)
+
+# Define the initial orbital elements of the big and small bodies
+avalb = rng.uniform(0.3, 2.0, Nb)
+avals = rng.uniform(0.3, 2.0, Ns)
+evalb = rng.uniform(0.0, 0.01, Nb)
+evals = rng.uniform(0.0, 0.01, Ns)
+incvalb = rng.uniform(0.0, 0.005 * 180 / np.pi, Nb)
+incvals = rng.uniform(0.0, 0.005 * 180 / np.pi, Ns)
+capomvalb = rng.uniform(0.0, 360.0, Nb)
+capomvals = rng.uniform(0.0, 360.0, Ns)
+omegavalb = rng.uniform(0.0, 360.0, Nb)
+omegavals = rng.uniform(0.0, 360.0, Ns)
+capmvalb = rng.uniform(0.0, 360.0, Nb)
+capmvals = rng.uniform(0.0, 360.0, Ns)
+Ipvalb = np.full((Nb,3), 0.4)
+Ipvals = np.full((Ns,3), 0.4)
+rotvalb = np.zeros_like(Ipvalb)
+rotvals = np.zeros_like(Ipvals)
+GMvalb = np.full(Nb, Mb * sim.GU)
+GMvals = np.full(Ns, Ms * sim.GU)
+Rvalb = np.full(Nb, Rb)
+Rvals = np.full(Ns, Rs)
+
+# Give the bodies unique names
+nameb = [f"Big{i:03}" for i in range(Nb)]
+names = [f"Small{i:03}" for i in range(Ns)]
+
+# Add the modern planets and the Sun using the JPL Horizons Database.
+sim.add_solar_system_body(["Sun","Jupiter","Saturn","Uranus","Neptune"])
+sim.add_body(name=nameb, a=avalb, e=evalb, inc=incvalb, capom=capomvalb, omega=omegavalb, capm=capmvalb, Gmass=GMvalb, radius=Rvalb, rot=rotvalb, Ip=Ipvalb)
+sim.add_body(name=names, a=avals, e=evals, inc=incvals, capom=capomvals, omega=omegavals, capm=capmvals, Gmass=GMvals, radius=Rvals, rot=rotvals, Ip=Ipvals)
+sim.set_parameter(mtiny=mtiny, minimum_fragment_mass=mininum_fragment_mass)
+
+sim.run(tstop=3e8, dt=6.0875/365.25, istep_out=60000, dump_cadence=1)
+