#################################################################
#
#                          Getting started
#
###################################################################


# Start Python, and at the prompt type:
from Cantera import *

# This statement imports the most commonly-used components of Cantera.

# Now type
gas1 = GRI30()
print gas1

# If you have successfully installed the Cantera package, 
# you should see something like this:
#
#
#       temperature                  300  K
#       pressure                  101325  Pa
#       density                 0.081896  kg/m^3
#       mean mol. weight         2.01594  amu
#
#                           X                 Y   
#                     -------------     ------------ 
#                H2   1.000000e+000     1.000000e+000
#
#
# What you have just done is to create an object ("gas1") that
# implements GRI-Mech 3.0, the 53-species, 325-reaction natural gas
# combustion mechanism developed by Gregory P. Smith, David M. Golden,
# Michael Frenklach, Nigel W. Moriarty, Boris Eiteneer, Mikhail
# Goldenberg, C. Thomas Bowman, Ronald K. Hanson, Soonho Song, William
# C. Gardiner, Jr., Vitali V. Lissianski, and Zhiwei Qin. See
# http://www.me.berkeley.edu/gri_mech/ for more information.
#
# The object created by GI30() has properties you would expect for a gas
# mixture - it has a temperature, a pressure, species mole and mass
# fractions, etc. As we'll soon see, it has many more properties.
#
# The summary of the state of 'gas1' printed above shows that new
# objects created by function GRI30() start out with a temperature of
# 300 K, a pressure of 1 atm, and have a composition that consists of
# only one species, in this case hydrogen. There is nothing special
# about H2 - it just happens to be the first species listed in the
# input file defining GRI-Mech 3.0 that the 'GRI30' function reads. In
# general, whichever species is listed first will initially have a
# mole fraction of 1.0, and all of the others will be zero.

# The printed summary only shows those species with non-zero mole
# fractions, so only H2 is shown, and the 52 other species are not
# listed. (More precisely, only species with mole fractions above a
# threshold value of 1.E-20 are shown.)


#  Setting the state
#  -----------------

# The state of the object can easily be changed. For example,

gas1.setTemperature(1200)

# sets the temperature to 1200 K. (Cantera always uses SI units.)
# After this statement,

print gas1

# results in:
#
#       temperature                 1200  K
#       pressure                  405300  Pa
#       density                 0.081896  kg/m^3
#       mean mol. weight         2.01594  amu
#
#                           X                 Y   
#                     -------------     ------------ 
#                H2   1.000000e+000     1.000000e+000
#
# Notice that the temperature has been changed as requested, but the
# pressure has changed too. The density and composition have
# not.
#
# When setting properties individually, some convention needs to be
# adopted to specify which other properties are held constant. This is
# because thermodynamics requires that *two* properties (not one) in
# addition to composition information be specified to fix the
# intensive state of a substance (or mixture).
#
# Cantera adopts the following convention: only one of the set
# (temperature, density, mass fractions) is altered by setting any
# single property. In particular:
#
# a) Setting the temperature is done holding density and
#    composition  fixed. (The pressure changes.)

# b) Setting the pressure is done holding temperature and
#    composition fixed. (The density changes.)
# 
# c) Setting the composition is done holding temperature
#    and density fixed. (The pressure changes).
#


# Setting multiple properties
# ---------------------------------------------------

# If you want to set multiple properties at once, use the 'set' function:

set(gas1, Temperature = 900.0, Pressure = 1.e5)

# This statement sets both temperature and pressure at the same
# time. Any number of property/value pairs can be specified in a
# call to 'set'. For example, the following sets the mole fractions
# too:

set(gas1, Temperature = 900.0, Pressure = 1.e5,
    MoleFractions = 'CH4:1,O2:2,N2:7.52')

# The 'set' function also accepts abbreviated property names:

set(gas1,T = 900.0, P = 1.e5, X = 'CH4:1,O2:2,N2:7.52')

# Either version results in
#
#       temperature                  900  K
#       pressure                  100000  Pa
#       density                   0.3693  kg/m^3
#       mean mol. weight         27.6332  amu
#
#                           X                 Y   
#                     -------------     ------------ 
#                O2   1.901141e-001     2.201489e-001
#               CH4   9.505703e-002     5.518732e-002
#                N2   7.148289e-001     7.246638e-001
#

# Other properties may also be set using 'set', including some that
# can't be set individually. The following property pairs may be
# set: (Enthalpy, Pressure), (IntEnergy, Volume), (Entropy,
# Volume), (Entropy, Pressure). In each case, the values of the
# extensive properties must be entered *per unit mass*. 

# Setting the enthalpy and pressure:
set(gas1, Enthalpy = 2*gas1.enthalpy_mass(), Pressure = 2*OneAtm)


# The composition above was specified using a string. The format is a
# comma-separated list of <species name>:<relative mole numbers>
# pairs. The mole numbers will be normalized to produce the mole
# fractions, and therefore they are 'relative' mole numbers.  Mass
# fractions can be set in this way too by changing 'X' to 'Y' in the
# above statement.

# The composition can also be set using an array, which must have the
# same size as the number of species. For example, to set all 53 mole
# fractions to the same value, do this:

x = ones(53,'d');   # NumPy array of 53 ones
set(gas1, X = x)
print gas1

# To set the mass fractions to equal values:
set(gas1, Y = x)
print gas1