99 lines
2.5 KiB
Python
Executable File
99 lines
2.5 KiB
Python
Executable File
#!/usr/bin/python
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# -*- coding:utf-8 -*-
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"""
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Class definition for physical atribute
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"""
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import numpy as np
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class Body:
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def __init__(self, mass, position, velocity):
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self.m = mass
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self.q = position
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self.v = velocity
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self.p = velocity*mass
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def __repr__(self): # Called upon "print(body)"
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return "Body of mass: {0:.2f}kg, position: {1}, velocity: {2}".format(self.m, self.p, self.v)
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def __str__(self): # Called upon "str(body)"
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return "Body of mass: {0:.2f}kg, position: {1}, velocity: {2}".format(self.m, self.p, self.v)
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class System:
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def __init__(self, bodylist):
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self.bodylist = bodylist
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def Mass(self): #return total system mass
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mass = 0
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for body in self.bodylist:
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mass = mass + body.m
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return mass
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def COM(self): #return center of mass in cartesian np_array
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coord = np.zeros(3)
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for body in self.bodylist:
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coord = coord + body.m*body.q
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coord = coord/self.Mass()
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return coord
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def Lval(self,Lbodylist): #return angular momentum of bodies in bodylist
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comcoord = np.zeros(3)
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for body in Lbodylist:
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comcoord = comcoord + body.m*body.q
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comcoord = comcoord/self.Mass()
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comq = np.zeros((len(Lbodylist),3))
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i = 0
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L = np.zeros(3)
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for body in Lbodylist:
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comq[i] = body.q-comcoord
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L = L + np.cross(comq[i],body.p)
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i = i+1
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return L
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def Eval(self,Lbodylist): #return total energy of bodies in bodylist
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G = 1. #Gravitational constant (here normalized)
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T = 0
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W = 0
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for body in Lbodylist:
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T = T + 1./2.*body.m*np.linalg.norm(body.v)**2
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for otherbody in Lbodylist:
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if body != otherbody:
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rij = np.linalg.norm(body.q-otherbody.q)
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W = W - G*body.m*otherbody.m/rij
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return T + W
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if __name__ == "__main__":
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# initialisation mass
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m1 = 10
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m2 = 1
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m3 = 1
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# initialisation position
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q1 = np.array([0, 0, 0])
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q2 = np.array([1, 0, 0])
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q3 = np.array([2, 0, 0])
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# initialisation velocity
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v1 = np.array([0, 0, 0])
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v2 = np.array([1, 1, 0])
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v3 = np.array([2, 0, 0])
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star1 = Body(m1,q1,v1)
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star2 = Body(m2,q2,v2)
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star3 = Body(m3,q3,v3)
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Lbodylist = [star1,star2]
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array = np.zeros((len(Lbodylist),3))
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array[0]=star3.q
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tribody = System([star1,star2,star3])
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print("list=",Lbodylist)
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print(tribody.Lval(Lbodylist))
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