def test_find_equilibrium_position():
bearing = flow.fluid_flow_example2()
find_equilibrium_position(bearing,
print_along=False,
tolerance=0.1,
increment_factor=0.01,
max_iterations=5,
increment_reduction_limit=1e-03)
assert_allclose(bearing.eccentricity,
(bearing.radius_stator - bearing.radius_rotor) * 0.2663,
atol=0.001)
def __init__(
self,
nz,
ntheta,
length,
omega,
p_in,
p_out,
radius_rotor,
radius_stator,
viscosity,
density,
attitude_angle=None,
eccentricity=None,
load=None,
omegap=None,
immediately_calculate_pressure_matrix_numerically=True,
bearing_type=None,
shape_geometry="cylindrical",
preload=0.4,
displacement=0,
max_depth=None,
):
self.nz = nz
self.ntheta = ntheta
self.n_interv_z = nz - 1
self.n_interv_theta = ntheta - 1
self.length = length
self.ltheta = 2.0 * np.pi
self.dz = length / self.n_interv_z
self.dtheta = self.ltheta / self.n_interv_theta
self.ntotal = self.nz * self.ntheta
self.omega = omega
self.p_in = p_in
self.p_out = p_out
self.radius_rotor = radius_rotor
self.radius_stator = radius_stator
self.viscosity = viscosity
self.density = density
self.characteristic_speed = self.omega * self.radius_rotor
self.radial_clearance = self.radius_stator - self.radius_rotor
self.bearing_type = bearing_type
if bearing_type is None:
if self.length / (2 * self.radius_stator) <= 1 / 4:
self.bearing_type = "short_bearing"
elif self.length / (2 * self.radius_stator) > 4:
self.bearing_type = "long_bearing"
else:
self.bearing_type = "medium_size"
self.shape_geometry = shape_geometry
self.preload = preload
self.displacement = displacement
self.max_depth = max_depth
self.eccentricity = eccentricity
self.attitude_angle = attitude_angle
self.eccentricity_ratio = None
self.load = load
self.omegap = omegap
if self.omegap is None:
self.omegap = self.omega
else:
self.omegap = omegap
self.z_list = np.zeros(self.nz)
self.re = np.zeros([self.nz, self.ntheta])
self.ri = np.zeros([self.nz, self.ntheta])
self.xre = np.zeros([self.nz, self.ntheta])
self.xri = np.zeros([self.nz, self.ntheta])
self.yre = np.zeros([self.nz, self.ntheta])
self.yri = np.zeros([self.nz, self.ntheta])
self.gama = np.zeros([self.nz, self.ntheta])
self.t = 0
self.xp = 0
self.yp = 0
if (self.bearing_type == "short_bearing"
and self.shape_geometry == "cylindrical"):
if self.eccentricity is None and load is not None:
modified_s = modified_sommerfeld_number(
self.radius_stator,
self.omega,
self.viscosity,
self.length,
self.load,
self.radial_clearance,
)
self.eccentricity_ratio = calculate_eccentricity_ratio(
modified_s)
self.eccentricity = (calculate_eccentricity_ratio(modified_s) *
self.radial_clearance)
if attitude_angle is None:
self.attitude_angle = calculate_attitude_angle(
self.eccentricity_ratio)
elif self.eccentricity is not None and load is not None:
modified_s = modified_sommerfeld_number(
self.radius_stator,
self.omega,
self.viscosity,
self.length,
self.load,
self.radial_clearance,
)
self.eccentricity_ratio = calculate_eccentricity_ratio(
modified_s)
if attitude_angle is None:
self.attitude_angle = calculate_attitude_angle(
self.eccentricity_ratio)
elif eccentricity is not None and load is None:
self.eccentricity_ratio = self.eccentricity / self.radial_clearance
self.load = calculate_rotor_load(
self.radius_stator,
self.omega,
self.viscosity,
self.length,
self.radial_clearance,
self.eccentricity_ratio,
)
if attitude_angle is None:
self.attitude_angle = calculate_attitude_angle(
self.eccentricity_ratio)
else:
sys.exit("Either load or eccentricity must be given.")
self.xi = self.eccentricity * np.cos(3 * np.pi / 2 +
self.attitude_angle)
self.yi = self.eccentricity * np.sin(3 * np.pi / 2 +
self.attitude_angle)
self.geometry_description()
else:
if load is not None:
find_equilibrium_position(self)
if eccentricity is not None:
self.eccentricity = eccentricity
if attitude_angle is not None:
self.attitude_angle = attitude_angle
else:
if attitude_angle is None:
sys.exit("Attitude angle or load must be given.")
if eccentricity is None:
sys.exit("Eccentricity or load must be given.")
self.geometry_description()
self.eccentricity_ratio = self.eccentricity / self.radial_clearance
self.xi = self.eccentricity * np.cos(3 * np.pi / 2 +
self.attitude_angle)
self.yi = self.eccentricity * np.sin(3 * np.pi / 2 +
self.attitude_angle)
self.p_mat_analytical = np.zeros([self.nz, self.ntheta])
self.p_mat_numerical = np.zeros([self.nz, self.ntheta])
self.analytical_pressure_matrix_available = False
self.numerical_pressure_matrix_available = False
if immediately_calculate_pressure_matrix_numerically:
self.calculate_pressure_matrix_numerical()
def test_find_equilibrium_position():
bearing = fluid_flow_short_friswell()
eccentricity = find_equilibrium_position(bearing, print_along=False)
assert_allclose(eccentricity,
(bearing.radius_stator - bearing.radius_rotor) * 0.2663,
rtol=0.0002)