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Isentropic, adiabatic flow (with units)#
Isentropic, adiabatic flow example - calculate area ratio vs. Mach number curve.
Uses the pint
library to include customized units in the calculation.
Requires: Cantera >= 3.0.0, pint
area ratio Mach number temperature pressure ratio
3.79E+01 5.52 167.33 K 1.00E-03
2.26E+01 4.85 211.20 K 2.15E-03
1.35E+01 4.24 264.80 K 4.64E-03
8.12E+00 3.68 330.41 K 1.00E-02
4.92E+00 3.15 411.12 K 2.15E-02
3.03E+00 2.64 511.08 K 4.64E-02
1.93E+00 2.15 635.31 K 1.00E-01
1.29E+00 1.66 788.71 K 2.15E-01
1.00E+00 1.11 975.16 K 4.64E-01
4.80E+06 0.00 1200.00 K 1.00E+00
import cantera.with_units as ctu
import numpy as np
# This sets the default output format of the units to have 2 significant digits
# and the units are printed with a Unicode font. See:
# https://pint.readthedocs.io/en/stable/user/formatting.html
if hasattr(ctu.cantera_units_registry, "formatter"): # pint >= 0.24
ctu.cantera_units_registry.formatter.default_format = ".2F~P"
else:
ctu.units.default_format = ".2F~P"
def soundspeed(gas):
"""The speed of sound. Assumes an ideal gas."""
gamma = gas.cp / gas.cv
specific_gas_constant = ctu.units.molar_gas_constant / gas.mean_molecular_weight
return np.sqrt(gamma * specific_gas_constant * gas.T).to("m/s")
def isentropic(gas=None):
"""
In this example, the area ratio vs. Mach number curve is computed. If a gas
object is supplied, it will be used for the calculations, with the
stagnation state given by the input gas state. Otherwise, the calculations
will be done for a 10:1 hydrogen/nitrogen mixture with stagnation T0 = 1700.33
degrees Fahrenheit, P0 = 10 atm.
"""
if gas is None:
gas = ctu.Solution('gri30.yaml')
gas.TPX = 2160 * ctu.units.degR, 10.0 * ctu.units.atm, 'H2:1,N2:0.1'
# get the stagnation state parameters
s0 = gas.s
h0 = gas.h
p0 = gas.P
mdot = 1 * ctu.units.kg / ctu.units.s # arbitrary
amin = 1.e14 * ctu.units.m**2
data = []
# compute values for a range of pressure ratios
p_range = np.logspace(-3, 0, 10) * p0
for p in p_range:
# set the state using (p,s0)
gas.SP = s0, p
v = np.sqrt(2.0*(h0 - gas.h)).to("m/s") # h + V^2/2 = h0
area = mdot/(gas.density*v) # rho*v*A = constant
amin = min(amin, area)
data.append([area, v/soundspeed(gas), gas.T, p/p0])
return data, amin
if __name__ == "__main__":
print(__doc__)
data, amin = isentropic()
label_string = "area ratio\tMach number\ttemperature\tpressure ratio"
output_string = "{0:.2E~P}\t{1} {2}\t{3:.2E~P}"
print(label_string)
for row in data:
print(output_string.format(row[0] / amin, row[1], row[2], row[3]))
Total running time of the script: (0 minutes 0.063 seconds)