88 lines
2.8 KiB
Python
Executable File
88 lines
2.8 KiB
Python
Executable File
#!/usr/bin/python
|
|
# -*- coding:utf-8 -*-
|
|
"""
|
|
Class definition for physical atribute
|
|
"""
|
|
import numpy as np
|
|
|
|
globals()['G'] = 6.67e-11 #Gravitational constant in SI units
|
|
globals()['Ms'] = 2e30 #Solar mass in kg
|
|
globals()['au'] = 1.5e11 #Astronomical unit in m
|
|
|
|
class Body:
|
|
|
|
def __init__(self, mass, position, velocity):
|
|
self.m = mass
|
|
self.q = position
|
|
self.v = velocity
|
|
self.p = velocity*mass
|
|
|
|
def __repr__(self): # Called upon "print(body)"
|
|
return "Body of mass: {0:.2f}kg, position: {1}, velocity: {2}".format(self.m, self.p, self.v)
|
|
|
|
def __str__(self): # Called upon "str(body)"
|
|
return "Body of mass: {0:.2f}kg, position: {1}, velocity: {2}".format(self.m, self.p, self.v)
|
|
|
|
class System:
|
|
|
|
def __init__(self, bodylist):
|
|
self.bodylist = bodylist
|
|
|
|
def get_masses(self): #return the masses of each object
|
|
return np.array([body.m for body in self.bodylist])
|
|
|
|
def get_positions(self): #return the positions of the bodies
|
|
return np.array([body.q for body in self.bodylist])
|
|
|
|
def get_momenta(self): #return the momenta of the bodies
|
|
return np.array([body.p for body in self.bodylist])
|
|
|
|
def Mass(self): #return total system mass
|
|
mass = 0
|
|
for body in self.bodylist:
|
|
mass = mass + body.m
|
|
return mass
|
|
|
|
def COM(self): #return center of mass in cartesian np_array
|
|
coord = np.zeros(3)
|
|
for body in self.bodylist:
|
|
coord = coord + body.m*body.q
|
|
coord = coord/self.Mass()
|
|
return coord
|
|
|
|
def COMV(self): #return center of mass velocity in cartesian np_array
|
|
coord = np.zeros(3)
|
|
for body in self.bodylist:
|
|
coord = coord + body.p
|
|
coord = coord/self.Mass()
|
|
return coord
|
|
|
|
def COMShift(self): #Shift coordinates of bodies in system to COM frame and set COM at rest
|
|
for body in self.bodylist:
|
|
body.q = body.q - self.COM()
|
|
body.p = body.p - self.COMV()
|
|
return 0
|
|
|
|
def Lval(self): #return angular momentum of bodies in system
|
|
L = np.zeros(3)
|
|
for body in self.bodylist:
|
|
L = L + np.cross(body.q,body.p)
|
|
return L
|
|
|
|
def Eval(self): #return total energy of bodies in system
|
|
T = 0
|
|
W = 0
|
|
for body in self.bodylist:
|
|
T = T + 1./2.*body.m*np.linalg.norm(body.v)**2
|
|
for otherbody in self.bodylist:
|
|
if body != otherbody:
|
|
rij = np.linalg.norm(body.q-otherbody.q)
|
|
W = W - G*body.m*otherbody.m/rij
|
|
return T + W
|
|
|
|
def __repr__(self): # Called upon "print(system)"
|
|
return str([print(body) for body in self.bodylist])
|
|
|
|
def __str__(self): # Called upon "str(system)"
|
|
return str([str(body) for body in self.bodylist])
|