From 5f6f2481f34e6b36a16244c5bd81490d136026e2 Mon Sep 17 00:00:00 2001
From: Dave Goodwin <dgg@caltech.edu>
Date: Fri, 21 Oct 2005 00:57:11 +0000
Subject: [PATCH] initial import

---
 .../examples/gasdynamics/soundSpeeds.py       | 50 +++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 Cantera/python/examples/gasdynamics/soundSpeeds.py

diff --git a/Cantera/python/examples/gasdynamics/soundSpeeds.py b/Cantera/python/examples/gasdynamics/soundSpeeds.py
new file mode 100644
index 000000000..a9d90da25
--- /dev/null
+++ b/Cantera/python/examples/gasdynamics/soundSpeeds.py
@@ -0,0 +1,50 @@
+from Cantera import *
+import math
+
+def equilSoundSpeeds(gas):
+
+    """Returns the equilibrium and frozen sound speeds for a gas.  The
+    gas is first set to an equilibrium state, since otherwise the
+    equilibrium sound speed is not defined. Therefore, both sound
+    speeds are for a gas with an equilibrium composition - not the
+    composition of the gas object on entry."""
+
+    # set the gas to equilibrium at its current T and P
+    gas.equilibrate('TP')
+
+    # save properties
+    s0 = gas.entropy_mass()
+    p0 = gas.pressure()
+    r0 = gas.density()
+
+    # perturb density
+    r1 = r0*1.0001
+
+    # set the gas to a state with the same entropy and composition but
+    # the perturbed density
+    gas.setState_SV(s0, 1.0/r1)
+
+    # save the pressure for this case for the frozen sound speed
+    pfrozen = gas.pressure()
+    
+    # now equilibrate the gas holding S and V constant
+    gas.equilibrate("SV")
+
+    p1 = gas.pressure()
+
+    aequil = math.sqrt((p1 - p0)/(r1 - r0));
+    afrozen = math.sqrt((pfrozen - p0)/(r1 - r0));    
+    return (aequil, afrozen)
+
+
+# test program
+if __name__ == "__main__":
+    
+    gas = GRI30()
+    gas.set(X = 'CH4:0.1.1, O2:2.0, N2:3.76')
+    for n in range(27):
+        temp = 300.0 + n*100.0
+        gas.set(T = temp, P = OneAtm)
+        print temp, equilSoundSpeeds(gas)
+
+