import numpy as np
from scipy.constants import atm, zero_Celsius
from ..mathutils.function import NUMERICAL_TYPES, Function
from ..plots.fluid_plots import _FluidPlots
from ..prints.fluid_prints import _FluidPrints
[docs]
class Fluid:
"""Class that represents a fluid object and its attributes,
such as density.
Attributes
----------
name : str
Name of the fluid.
density : int, float, callable, string, array, Function
Input density of the fluid in kg/m³.
Used internally to compute the density_function.
density_function : Function
Density of the fluid as a function of temperature and pressure.
"""
[docs]
def __init__(self, name, density):
"""Initializes a Fluid object.
Parameters
----------
name : str
Name of the fluid.
density : int, float, callable, string, array, Function
Density of the fluid in kg/m³ as a function of temperature
and pressure. If a int or float is given, it is considered
a constant function. A callable, csv file or an list of points
can be given to express the density values.
The parameter is used as a ``Function`` source.
See more on :class:`rocketpy.Function` source types.
"""
self.name = name
self.density = density
self.density_function = density
self.prints = _FluidPrints(self)
self.plots = _FluidPlots(self)
@property
def density(self):
"""Density of the fluid from the class parameter input."""
return self._density
@density.setter
def density(self, value):
"""Setter of the density class parameter."""
if isinstance(value, NUMERICAL_TYPES):
# Numerical value kept for retro-compatibility
self._density = value
else:
self._density = Function(
value,
interpolation="linear",
extrapolation="natural",
inputs=["Temperature (K)", "Pressure (Pa)"],
outputs="Density (kg/m³)",
)
@property
def density_function(self):
"""Density of the fluid as a function of temperature and pressure."""
return self._density_function
@density_function.setter
def density_function(self, value):
"""Setter for the density function of the fluid. Numeric values
are converted to constant functions.
Parameters
----------
value : int, float, callable, string, array, Function
Density of the fluid in kg/m³ as a function of temperature
and pressure. The value is used as a ``Function`` source.
"""
if isinstance(value, NUMERICAL_TYPES):
# pylint: disable=unused-argument
def density_function(temperature, pressure):
return value
else:
density_function = value
self._density_function = Function(
density_function,
interpolation="linear",
extrapolation="natural",
inputs=["Temperature (K)", "Pressure (Pa)"],
outputs="Density (kg/m³)",
)
[docs]
def get_time_variable_density(self, temperature, pressure):
"""Get the density of the fluid as a function of time.
Parameters
----------
temperature : Function
Temperature of the fluid in Kelvin.
pressure : Function
Pressure of the fluid in Pascals.
Returns
-------
Function
Density of the fluid in kg/m³ as function of time.
"""
is_temperature_callable = callable(temperature.source)
is_pressure_callable = callable(pressure.source)
if is_temperature_callable and is_pressure_callable:
return Function(
lambda time: self.density_function.get_value(
temperature.source(time), pressure.source(time)
),
inputs="Time (s)",
outputs="Density (kg/m³)",
)
if is_temperature_callable or is_pressure_callable:
time_scale = (
temperature.x_array if not is_temperature_callable else pressure.x_array
)
else:
time_scale = np.unique(
np.concatenate((temperature.x_array, pressure.x_array))
)
density_time = self.density_function.get_value(
temperature.get_value(time_scale), pressure.get_value(time_scale)
)
return Function(
np.column_stack((time_scale, density_time)),
interpolation="linear",
extrapolation="constant",
inputs="Time (s)",
outputs="Density (kg/m³)",
)
[docs]
def __repr__(self):
"""Representation method.
Returns
-------
str
String representation of the class.
"""
return f"Fluid(name={self.name}, density={self.density})"
[docs]
def __str__(self):
"""String method.
Returns
-------
str
String representation of the class.
"""
return f"Fluid: {self.name}"
def to_dict(self, **kwargs): # pylint: disable=unused-argument
discretize = kwargs.get("discretize", False)
density = self.density
if discretize and isinstance(density, Function):
density = density.set_discrete(
lower=(100, atm * 0.9),
upper=(zero_Celsius + 30, atm * 50),
samples=(25, 25),
mutate_self=False,
)
return {"name": self.name, "density": density}
@classmethod
def from_dict(cls, data):
return cls(data["name"], data["density"])
