79 lines
1.8 KiB
Python
Executable file
79 lines
1.8 KiB
Python
Executable file
from Cantera import *
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from Numeric import zeros
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import math
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def soundspeed(gas):
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"""The speed of sound. Assumes an ideal gas."""
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# if gas.isIdealGas():
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gamma = gas.cp_mass()/gas.cv_mass()
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return math.sqrt(gamma * GasConstant
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* gas.temperature() / gas.meanMolecularWeight() )
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#else:
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# raise "non-ideal not implemented."
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def isentropic(g = None):
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"""
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ISENTROPIC isentropic, adiabatic flow example
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In this example, the area ratio vs. Mach number curve is
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computed. If a gas object is supplied, it will be used for the
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calculations, with the stagnation state given by the input gas
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state. Otherwise, the calculations will be done for a 10:1
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hydrogen/nitrogen mixture with stagnation T0 = 1200 K, P0 = 10
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atm.
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"""
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if g == None:
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gas = GRI30()
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gas.set(T = 1200.0,P = 10.0*OneAtm,X = 'H2:1,N2:0.1')
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else:
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gas = g
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# get the stagnation state parameters
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s0 = gas.entropy_mass()
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h0 = gas.enthalpy_mass()
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p0 = gas.pressure()
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mdot = 1 # arbitrary
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amin = 1.e14
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data = zeros((200,4),'d')
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# compute values for a range of pressure ratios
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for r in range(200):
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p = p0*(r+1)/201.0
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# set the state using (p,s0)
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gas.set(S = s0, P = p)
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h = gas.enthalpy_mass()
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rho = gas.density()
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v2 = 2.0*(h0 - h) # h + V^2/2 = h0
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v = math.sqrt(v2)
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area = mdot/(rho*v); # rho*v*A = constant
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if area < amin: amin = area
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data[r,:] = [area, v/soundspeed(gas), gas.temperature(), p/p0]
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data[:,0] /= amin
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return data
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if __name__ == "__main__":
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print isentropic.__doc__
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data = isentropic()
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print 'area ratio, Mach number, temperature, pressure ratio'
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print data
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