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 __init__(
self,
nz,
ntheta,
nradius,
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,
):
if load is None and eccentricity is None:
sys.exit("Either load or eccentricity must be given.")
self.nz = nz
self.ntheta = ntheta
self.nradius = nradius
self.n_interv_z = nz - 1
self.n_interv_theta = ntheta - 1
self.n_interv_radius = nradius - 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 = ""
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.eccentricity = eccentricity
self.eccentricity_ratio = None
self.load = load
if self.eccentricity is None:
modified_s = modified_sommerfeld_number(
self.radius_stator,
self.omega,
self.viscosity,
self.length,
self.load,
self.radial_clearance,
)
self.eccentricity = (
calculate_eccentricity_ratio(modified_s) * self.radial_clearance
)
self.omegap = omegap
if self.omegap is None:
self.omegap = self.omega
else:
self.omegap = omegap
self.eccentricity_ratio = self.eccentricity / self.radial_clearance
if self.load is None:
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:
self.attitude_angle = attitude_angle
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.re = np.zeros([self.nz, self.ntheta])
self.ri = np.zeros([self.nz, self.ntheta])
self.z_list = np.zeros(self.nz)
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.p_mat_analytical = np.zeros([self.nz, self.ntheta])
self.c1 = np.zeros([self.nz, self.ntheta])
self.c2 = np.zeros([self.nz, self.ntheta])
self.c0w = np.zeros([self.nz, self.ntheta])
self.M = np.zeros([self.ntotal, self.ntotal])
self.f = np.zeros([self.ntotal, 1])
self.P = np.zeros([self.ntotal, 1])
self.p_mat_numerical = np.zeros([self.nz, self.ntheta])
self.gama = np.zeros([self.nz, self.ntheta])
self.calculate_coefficients()
self.analytical_pressure_matrix_available = False
self.numerical_pressure_matrix_available = False
self.calculate_pressure_matrix_numerical()
if immediately_calculate_pressure_matrix_numerically:
self.calculate_pressure_matrix_numerical()
def find_equilibrium_position(fluid_flow_object,
print_along=True,
relative_tolerance=1e-07,
numerical_fit=False):
"""This function returns an eccentricity value with calculated forces matching the load applied,
meaning an equilibrium position of the rotor.
Parameters
----------
fluid_flow_object: A FluidFlow object.
print_along: bool, optional
If True, prints the iteration process.
relative_tolerance: float, optional
numerical_fit: bool, optional
If True, it makes sure the result matches numerically, changing attributes of the
FluidFlow object.
Returns
-------
float
Eccentricity of the equilibrium position.
Examples
--------
>>> from ross.fluid_flow.fluid_flow import fluid_flow_example2
>>> my_fluid_flow = fluid_flow_example2()
>>> find_equilibrium_position(my_fluid_flow, print_along=False) # doctest: +ELLIPSIS
0.00010000...
"""
fluid_flow_object.calculate_pressure_matrix_numerical()
load = calculate_rotor_load(fluid_flow_object.radius_stator,
fluid_flow_object.omega,
fluid_flow_object.viscosity,
fluid_flow_object.length,
fluid_flow_object.radial_clearance,
fluid_flow_object.eccentricity_ratio)
error = (load - fluid_flow_object.load) / fluid_flow_object.load
increment = 0.1
k = 0
eccentricity = fluid_flow_object.eccentricity
while np.abs(error) > relative_tolerance:
eccentricity = eccentricity + (eccentricity * increment)
eccentricity_ratio = eccentricity / fluid_flow_object.difference_between_radius
load = calculate_rotor_load(fluid_flow_object.radius_stator,
fluid_flow_object.omega,
fluid_flow_object.viscosity,
fluid_flow_object.length,
fluid_flow_object.radial_clearance,
eccentricity_ratio)
new_error = (load - fluid_flow_object.load) / fluid_flow_object.load
if print_along:
print("Iteration " + str(k))
print("Eccentricity: " + str(eccentricity))
print("Load: " + str(load))
print("Error: " + str(new_error))
if error * new_error < 0:
if print_along:
print(
"Error changed sign. Changing sign of increment and reducing it."
)
increment = -increment / 10
elif abs(new_error) > abs(error):
if print_along:
print(
"Error was greater than previous one. Changing sign of increment and slightly "
"reducing it.")
increment = -increment / 5
error = new_error
k += 1
if print_along:
print()
return eccentricity