Skip to content

Latest commit

 

History

History
129 lines (101 loc) · 5.58 KB

connectorGravityTest.rst

File metadata and controls

129 lines (101 loc) · 5.58 KB
Raw

connectorGravityTest.py

You can view and download this file on Github: connectorGravityTest.py

#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# This is an EXUDYN example
#
# Details:  Test model for ObjectConnectorGravity, realizing gravitational forces between
#           two masses (used for astrospace or small-scale astronomical investigations, e.g., satellites);
#           in this case we simulate a small planetary system, initializing planets with orbital velocity
#
# Author:   Johannes Gerstmayr
# Date:     2022-01-30
#
# Copyright:This file is part of Exudyn. Exudyn is free software. You can redistribute it and/or modify it under the terms of the Exudyn license. See 'LICENSE.txt' for more details.
#
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
import sys
sys.path.append('../TestModels')

import exudyn as exu
from exudyn.itemInterface import *
from exudyn.utilities import * #includes itemInterface and rigidBodyUtilities
import exudyn.graphics as graphics #only import if it does not conflict
import numpy as np

useGraphics = True #without test
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#you can erase the following lines and all exudynTestGlobals related operations if this is not intended to be used as TestModel:
try: #only if called from test suite
    from modelUnitTests import exudynTestGlobals #for globally storing test results
    useGraphics = exudynTestGlobals.useGraphics
except:
    class ExudynTestGlobals:
        pass
    exudynTestGlobals = ExudynTestGlobals()
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

#create an environment for mini example
SC = exu.SystemContainer()
mbs = SC.AddSystem()

#some drawing properties, to see the objects ...
massStar = 1e20
massSatellite = 1e3
mass = [massSatellite, massSatellite, massSatellite, massSatellite]
sizeMass0 = 1e5 #just for drawing
sizeMass = [2e4,2e4,2e4,2e4] #just for drawing
rOrbit = [2e5, 4e5, 8e5, 10e5]
vOrbitEps = [1.,1.,1.,1.] #factors to make non-circular orbits...

background = graphics.CheckerBoard(point=[0,0,-2*sizeMass0], size=2.1*max(rOrbit),
                                      color=[0,0,0,1], alternatingColor=[0.05,0,0,1])

oGround=mbs.AddObject(ObjectGround(referencePosition= [0,0,0],
                                   visualization=VObjectGround(graphicsData=[background])))
# nGround = mbs.AddNode(NodePointGround(referenceCoordinates=[0,0,0]))
node0 = mbs.AddNode(NodePoint(referenceCoordinates = [0,0,0])) #planet
gMass0 = graphics.Sphere(radius=1e5, color=graphics.color.blue, nTiles=64)
oMassPoint0 = mbs.AddObject(MassPoint(nodeNumber = node0, physicsMass=massStar,
                                      visualization=VMassPoint(graphicsData=[gMass0])))
m0 = mbs.AddMarker(MarkerNodePosition(nodeNumber=node0))

#create satellites:
for i,r in enumerate(rOrbit):
    G = 6.6743e-11
    vOrbit = vOrbitEps[i]*np.sqrt(G*massStar/r) #orbital velocity, assumption of heavy star
    #exu.Print('vOrbit'+str(i)+'=',vOrbit)
    node1 = mbs.AddNode(NodePoint(referenceCoordinates = [r,0,0],
                                  initialVelocities=[0,vOrbit,0])) #satellite

    gMass1 = graphics.Sphere(radius=sizeMass[i], color=graphics.colorList[i], nTiles=24)

    oMassPoint1 = mbs.AddObject(MassPoint(nodeNumber = node1, physicsMass=mass[i],
                                          visualization=VMassPoint(graphicsData=[gMass1])))

    m1 = mbs.AddMarker(MarkerNodePosition(nodeNumber=node1))

    mbs.AddObject(ObjectConnectorGravity(markerNumbers=[m0,m1],
                                         mass0 = massStar, mass1=mass[i]))

#assemble and solve system for default parameters
mbs.Assemble()
simulationSettings = exu.SimulationSettings()

tEnd = 1e6
h = 1000
simulationSettings.solutionSettings.writeSolutionToFile = False
simulationSettings.timeIntegration.numberOfSteps = int(tEnd/h)
simulationSettings.timeIntegration.endTime = tEnd
simulationSettings.timeIntegration.generalizedAlpha.spectralRadius = 1
simulationSettings.timeIntegration.newton.useModifiedNewton = True

simulationSettings.displayStatistics = True
simulationSettings.timeIntegration.verboseMode = 1

# SC.visualizationSettings.nodes.drawNodesAsPoint = False

if useGraphics:
    exu.StartRenderer()              #start graphics visualization
    mbs.WaitForUserToContinue()    #wait for pressing SPACE bar to continue

#start solver:
# mbs.SolveDynamic(simulationSettings, solverType = exu.DynamicSolverType.TrapezoidalIndex2)
#gives 7 digits of accuracy for tEnd=1e6, h=1e3:
mbs.SolveDynamic(simulationSettings, solverType = exu.DynamicSolverType.RK67)

if useGraphics:
    SC.WaitForRenderEngineStopFlag()#wait for pressing 'Q' to quit
    exu.StopRenderer()               #safely close rendering window!

#check result at default integration time
#node1 is last node
pos = mbs.GetNodeOutput(node1, exu.OutputVariableType.Position)

exudynTestGlobals.testResult = pos[0] + pos[1] + pos[2]

exu.Print("result for ObjectConnectorGravity =", exudynTestGlobals.testResult)
#exudynTestGlobals.testResult = 1014867.2330320379