From 1d3a25453057ccff10b48bf7241c29239a98b6f9 Mon Sep 17 00:00:00 2001
From: Dave Goodwin <dgg@caltech.edu>
Date: Fri, 14 May 2004 21:15:23 +0000
Subject: [PATCH] added ability to compute mixture-averaged diffusion
 coefficients in class MultiTransport.

---
 Cantera/src/transport/MultiTransport.cpp | 37 ++++++++++++++++++++++--
 Cantera/src/transport/MultiTransport.h   |  5 ++++
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/Cantera/src/transport/MultiTransport.cpp b/Cantera/src/transport/MultiTransport.cpp
index f7ac3a31e..23bf98743 100755
--- a/Cantera/src/transport/MultiTransport.cpp
+++ b/Cantera/src/transport/MultiTransport.cpp
@@ -550,8 +550,8 @@ namespace Cantera {
         // invert L00,00
         int ierr = invert(m_Lmatrix, m_nsp);
         if (ierr != 0) {
-            cout << " invert returned ierr = " << ierr << endl;
-            exit(1);
+            throw CanteraError("MultiTransport::getMultiDiffCoeffs",
+                string(" invert returned ierr = ")+int2str(ierr));
         }
         m_l0000_ok = false;           // matrix is overwritten by inverse
 
@@ -569,6 +569,39 @@ namespace Cantera {
         }
     }
 
+
+    void MultiTransport::getMixDiffCoeffs(doublereal* d) {
+
+        // update the mole fractions
+        updateTransport_C();
+
+        // update the binary diffusion coefficients if necessary
+        updateDiff_T();
+
+        int k, j;
+        doublereal mmw = m_thermo->meanMolecularWeight();
+        doublereal sumxw = 0.0, sum2;
+        doublereal p = pressure_ig();
+	if (m_nsp == 1) {
+	  d[0] = m_bdiff(0,0) / p;
+	} else {
+	  for (k = 0; k < m_nsp; k++) sumxw += m_molefracs[k] * m_mw[k];
+	  for (k = 0; k < m_nsp; k++) {
+            sum2 = 0.0;
+            for (j = 0; j < m_nsp; j++) {
+	      if (j != k) {
+		sum2 += m_molefracs[j] / m_bdiff(j,k);
+	      }
+            }
+	    if (sum2 <= 0.0) {
+	      d[k] = m_bdiff(k,k) / p;
+	    } else {
+	      d[k] = (sumxw - m_molefracs[k] * m_mw[k])/(p * mmw * sum2);
+	    }
+	  }
+	}
+    }
+
               
     void MultiTransport::updateTransport_T() {
         //m_thermo->update_T(m_update_transport_T);
diff --git a/Cantera/src/transport/MultiTransport.h b/Cantera/src/transport/MultiTransport.h
index 670385a45..9c61ffc2c 100755
--- a/Cantera/src/transport/MultiTransport.h
+++ b/Cantera/src/transport/MultiTransport.h
@@ -97,6 +97,11 @@ namespace Cantera {
         virtual void getBinaryDiffCoeffs(int ld, doublereal* d);
         virtual void getMultiDiffCoeffs(int ld, doublereal* d);
 
+        /// Although this class implements a multicomponent diffusion
+        /// model, it is convenient to be able to compute
+        /// mixture-averaged diffusion coefficients too. 
+        virtual void getMixDiffCoeffs(doublereal* d);
+
 
         virtual void getSpeciesFluxes(int ndim, 
         doublereal* grad_T, int ldx, const doublereal* grad_X,