def testHangingCableANCF(self):
g = np.array([0., 0., -9.81])
system = fsi.ProtChSystem()
system.ChSystem.Set_G_acc(chrono.ChVectorD(g[0], g[1], g[2]))
system.setTimeStep(1e-1)
# timestepper = chrono.ChTimestepperEulerImplicitLinearized()
# system.ChSystem.SetTimestepper(timestepper)
solver = chrono.ChSolverMINRES()
system.ChSystem.SetSolver(solver)
solver.SetMaxIterations(100)
solver.EnableWarmStart(True)
solver.EnableDiagonalPreconditioner(True)
solver.SetVerbose(True)
system.ChSystem.SetSolverForceTolerance(1e-10)
system.ChSystem.SetSolverMaxIterations(100)
mesh = fsi.ProtChMesh(system)
L = np.array([5.])
nb_elems = np.array([3])
d = np.array([1e-3])
rho = np.array([1000.])
E = np.array([1e10])
cable_type = b"CableANCF"
fairlead_body = fsi.ProtChBody(system)
fairlead_body.ChBody.SetBodyFixed(True)
mooring = fsi.ProtChMoorings(system=system,
mesh=mesh,
length=L,
nb_elems=nb_elems,
d=d,
rho=rho,
E=E,
beam_type=cable_type)
mooring.external_forces_manual = True # tri: should work without this line
# vertical cable
mooring.setNodesPositionFunction(lambda s: np.array([0., 0., s]),
lambda s: np.array([0., 0., 1.]))
mooring.setNodesPosition()
mooring.buildNodes()
mooring.attachBackNodeToBody(fairlead_body)
system.calculate_init()
system.calculate(0.5)
T = mooring.getTensionBack()
strain = mooring.getNodesTension(eta=1.)[-1] * np.pi * d**2 / 4 * E
T_sol = -np.ones(3) * g * rho * (np.pi * d**2 / 4. * L)
npt.assert_almost_equal(-T, T_sol)
body2.barycenter0 = np.zeros(3)
# fix anchor in space
body2.ChBody.SetBodyFixed(True)
# MESH
# initialize mesh that will be used for cables
mesh = fsi.ProtChMesh(system)
# FEM CABLES
# moorings line 1
m1 = fsi.ProtChMoorings(system=system,
mesh=mesh,
length=np.array([L]),
nb_elems=np.array([nb_elems]),
d=np.array([d]),
rho=np.array([dens]),
E=np.array([E]))
m1.setName(b'mooring1')
# send position functions from catenary to FEM cable
m1.setNodesPositionFunction(cat1.s2xyz, cat1.ds2xyz)
# sets node positions of the cable
m1.setNodesPosition()
# build cable
m1.buildNodes()
# apply external forces
m1.setApplyDrag(True)
m1.setApplyBuoyancy(True)
m1.setApplyAddedMass(True)
# set fluid density at cable nodes