# encoding: utf-8
# 2013 © Václav Šmilauer <eu@doxos.eu>
import unittest
from minieigen import *
import woo.core
import woo.dem
import woo.utils
from woo.dem import *
[docs]class TestHertz(unittest.TestCase):
'Test :obj:`Law2_L6Geom_HertzPhys_DMT`.'
[docs] def setUp(self):
S=self.S=woo.core.Scene(fields=[woo.dem.DemField()])
m=HertzMat(density=1e3,young=1e8,ktDivKn=.2,tanPhi=.5,surfEnergy=0,alpha=0) # no adhesion
S.dem.par.add([
woo.utils.sphere((0,0,0),.05,fixed=False,wire=True,mat=m),
woo.utils.sphere((0,.10001,0),.05,fixed=False,wire=True,mat=m)
])
# dtSafety=0.4 work with 1% relative tolerance,
# dtSafety=0.8 makes collision time not fit within 1%.
S.dtSafety=0.4
S.engines=woo.utils.defaultEngines(damping=.0,cp2=Cp2_HertzMat_HertzPhys(en=0,label='cp2',poisson=.2),law=Law2_L6Geom_HertzPhys_DMT(),dynDtPeriod=10)+[
# -123 is replaced by v0 before actually used
LawTester(ids=(0,1),abWeight=.5,stages=[
LawTesterStage(values=(-123,0,0,0,0,0),whats='ivv...',until='stage.rebound',done='S.stop(); S.lab.tester.dead=True')]
,label='tester'
)
]
[docs] def testElasticCollisionTime(self):
'Hertz: elastic collision time for different impact velocities (simulation/analytic)'
S=self.S
S.lab.en=0 # no viscosity
E1,E2=S.dem.par[0].material.young,S.dem.par[1].material.young
nu1,nu2=S.lab.cp2.poisson,S.lab.cp2.poisson
d=S.dem.par[0].shape.radius+S.dem.par[1].shape.radius
rho=S.dem.par[0].material.density
Eeff=(E1*E2)/(E2*(1-nu1**2)+E1*(1-nu2**2))
for v0 in (1,1e-1,1e-2,1e-3,1e-4,1e-5):
S.lab.tester.stages[0].values[0]=-v0
S.lab.tester.dead=False
S.lab.tester.restart()
S.run(); S.wait()
def tauHertz(rho,Eeff,d,v0): return 2.214*(rho/Eeff)**(2/5.)*(d/v0**(1/5.))
#print 'Collision time with v0=%g: %g sim, %g analytical'%(v0,S.lab.tester.stages[0].cTime,tauHertz(rho,Eeff,d,v0))
delta=0.01*S.lab.tester.stages[0].cTime # 1% relative tolerance
self.assertAlmostEqual(S.lab.tester.stages[0].cTime,tauHertz(rho,Eeff,d,v0),delta=delta)
#self.assertTrue(1==1)