6cb4bd93ce
4 spaces per indentation level, no tabs, no trailing whitespace, and a single newline at end of each file.
61 lines
1.7 KiB
Python
61 lines
1.7 KiB
Python
from Cantera import *
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import math
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def equilSoundSpeeds(gas, rtol = 1.0e-6, maxiter = 5000):
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"""Returns a tuple containing the equilibrium and frozen sound
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speeds for a gas with an equilibrium composition. The gas is
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first set to an equilibrium state at the temperature and pressure
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of the gas, since otherwise the equilibrium sound speed is not
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defined.
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"""
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# set the gas to equilibrium at its current T and P
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gas.equilibrate('TP', rtol = rtol, maxiter = maxiter)
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# save properties
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s0 = gas.entropy_mass()
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p0 = gas.pressure()
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r0 = gas.density()
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# perturb the pressure
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p1 = p0*1.0001
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# set the gas to a state with the same entropy and composition but
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# the perturbed pressure
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gas.set(S = s0, P = p1)
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# save the density for this case for the frozen sound speed
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rho_frozen = gas.density()
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# now equilibrate the gas holding S and P constant
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gas.equilibrate("SP", loglevel=0, rtol = rtol, maxiter = maxiter) # , rtol = 1.0e-3, maxsteps=10000)
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r1 = gas.density()
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# equilibrium sound speed
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aequil = math.sqrt((p1 - p0)/(r1 - r0));
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# frozen sound speed
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afrozen = math.sqrt((p1 - p0)/(rho_frozen - r0));
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# compute the frozen sound speed using the ideal gas
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# expression as a check
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cp = gas.cp_mass()
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cv = gas.cv_mass()
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gamma = cp/cv
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afrozen2 = math.sqrt(gamma*GasConstant*gas.temperature()
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/gas.meanMolecularWeight())
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return (aequil, afrozen, afrozen2)
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# test program
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if __name__ == "__main__":
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gas = GRI30()
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gas.set(X = 'CH4:1.00, O2:2.0, N2:7.52')
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for n in range(27):
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temp = 300.0 + n*100.0
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gas.set(T = temp, P = OneAtm)
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print temp, equilSoundSpeeds(gas)
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