setup: Initialize N-body simulation

In nbody: Gravitational N-Body Simulation

Initialize N-body simulation

Description

Routines to generate the structured lists of initial conditions and simulation parameters required to run an N-body simulation with run.simulation.

Usage

setup()

setup.halley(
  t.max = NULL,
  nperiods = 1,
  dt.out = 1e+07,
  e = 0.96714,
  s = 2.667928e+12,
  ...
)

setup.sunearth(t.max = 31557600, dt.out = 86400 * 7, ...)

setup.ellipse(t.max = NULL, nperiods = 1, e = 0.9, s = 1, f = 0.5, ...)

setup.periodic.3body(
  v1 = 0.347112813567242,
  v2 = 0.532726851767674,
  t.max = 6.325,
  m3 = 1,
  ...
)

setup.pythagoras(t.max = 68, integrator = "yoshida6", eta = 0.002, ...)

Arguments

t.max	final simulation time
nperiods	number of orbital periods to be computed; ignored if t.max is specified.
dt.out	time step for simulation output
e	eccentricity in setup.ellipse()
s	semi-major axis in setup.ellipse()
...	other simulation parameters used by run.simulation
f	mass-ratio in setup.ellipse()
v1	first velocity parameter in setup.3body.periodic()
v2	second velocity parameter in setup.3body.periodic()
m3	mass of third body in setup.3body.periodic()
integrator	integrator used for N-body simulation, see run.simulation for details.
eta	accuracy parameter of adaptive time step, see run.simulation for details.

Value

Calling setup() is identical to calling setup.halley()

setup.halley() sets up a 2-body simulation of Halley's Comet around the Sun.

setup.sunearth() sets up a simple 2-body simulation of the Earth around the Sun, using only approximate orbital specifications.

setup.ellipse() sets up an elliptical Keplerian orbit in natural units

setup.periodic.3body() can be used to set up a planar zero angular momentum stable 3-body problem with two unit masses and a third mass m3 (maybe equal of different from unity). Such situations can be parameterized with two parameters v1 and v2, following the publications found at https://arxiv.org/abs/1709.04775 and https://arxiv.org/abs/1705.00527.
The default is the famous figure-of-eight, but try, for example, setup.3body.periodic(0.2034916865234370, 0.5181128588867190, 32.850, dt.out=0.02), setup.3body.periodic(0.2009656237, 0.2431076328, 19.0134164290, 0.5, dt.out=0.01) or setup.3body.periodic(0.991198122, 0.711947212, 17.650780784, 4, eta=0.005, dt.out=0.002).

setup.pythagoras() sets up the Pythagorean three-body problem consisting of three unit masses placed at the vertices of a right triangle with side lengths 3, 4 and 5. The masses are initially at rest and the gravitational constant is unity.

Author(s)

Danail Obreschkow

Examples

sim = setup.halley()
sim = run.simulation(sim)
plot(sim)

nbody documentation built on Sept. 11, 2024, 7:47 p.m.