/usr/lib/python2.7/dist-packages/gastables/PrandtlMeyer.py is in python-gastables 0.3-2.2.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | """ Python module for Prandtl Meyer functions with Mach angles
Assumptions:
1) Perfect gas with constant specific heats and molecular weights
2) Isentropic flow
"""
"""
* Copyright (C) 2006 Varun Hiremath.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* Authors: Varun Hiremath, Venkattraman A
* Version 0.2
"""
from scipy import optimize
from math import *
class PrandtlMeyer:
def __init__(self, g=1.4):
""" g is the value of gamma (ratio of specific heats), default = 1.4
"""
self.g = g
def get_Prandtl_Func_from_M(self, M):
""" Returns Prandtl Meyer function (degrees) corresponding to the given
Mach No. """
return (sqrt((self.g+1)/(self.g-1))* atan(sqrt((self.g-1)/(self.g+1)*(M**2 - 1))) - atan(sqrt(M**2 -1)))*180.0/pi
def get_Mach_Angle_from_M(self, M):
""" Returns Mach Angle (degrees) for a given Mach No. M """
return asin(1.0/M)*180.0/pi
def get_M_from_Prandtl_Func(self, omega):
""" Returns Mach No. corresponding to the given Prandtl
function value omega (degrees) """
return optimize.fsolve(lambda M: self.get_Prandtl_Func_from_M(M) - omega, 1.01)
def get_M_from_Mach_Angle(self, alpha):
""" Returns Mach No. corresponding to the given Mach Angle
alpha (degrees)"""
alpha = alpha*pi/180.0
return 1.0/sin(alpha)
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