Fix a couple of things which could lead to regression test failures

solvers/CompressibleFlowSolver/CMakeLists.txt

@@ -64,14 +64,17 @@ IF( NEKTAR_SOLVER_COMPRESSIBLE_FLOW )
     ADD_NEKTAR_TEST(CylinderSubsonic_NS_FRHU_LFRHU_SEM_3DHOMO1D_MVM)
     ADD_NEKTAR_TEST(Couette_FRSD_LFRSD_MODIFIED_3DHOMO1D_MVM)
     ADD_NEKTAR_TEST(CylinderSubsonic_NS_FRSD_LFRSD_MODIFIED_3DHOMO1D_MVM)
-    ADD_NEKTAR_TEST(Perturbation_M05_square_CBC_par)
-    ADD_NEKTAR_TEST(Perturbation_M05_square_CBC_back_par)
-    ADD_NEKTAR_TEST(Perturbation_M15_square_CBC_par)
-    ADD_NEKTAR_TEST(Perturbation_M15_square_CBC_back_par)
-    ADD_NEKTAR_TEST(Perturbation_M05_circle_CBC_back_par)
-    ADD_NEKTAR_TEST(Perturbation_M15_circle_CBC_back_par)
-    ADD_NEKTAR_TEST(Perturbation_NS_M05_square_CBC_par)
-    ADD_NEKTAR_TEST(Perturbation_NS_M15_square_CBC_par)
+
+    IF (NEKTAR_USE_MPI)
+        ADD_NEKTAR_TEST(Perturbation_M05_square_CBC_par)
+        ADD_NEKTAR_TEST(Perturbation_M05_square_CBC_back_par)
+        ADD_NEKTAR_TEST(Perturbation_M15_square_CBC_par)
+        ADD_NEKTAR_TEST(Perturbation_M15_square_CBC_back_par)
+        ADD_NEKTAR_TEST(Perturbation_M05_circle_CBC_back_par)
+        ADD_NEKTAR_TEST(Perturbation_M15_circle_CBC_back_par)
+        ADD_NEKTAR_TEST(Perturbation_NS_M05_square_CBC_par)
+        ADD_NEKTAR_TEST(Perturbation_NS_M15_square_CBC_par)
+    ENDIF (NEKTAR_USE_MPI)
 
     IF (NEKTAR_USE_FFTW)
 	ADD_NEKTAR_TEST(Couette_WeakDG_LDG_SEM_3DHOMO1D_FFT)

solvers/CompressibleFlowSolver/EquationSystems/CompressibleFlowSystem.cpp

@@ -896,7 +896,7 @@ namespace Nektar
               Array<OneD, Array<OneD, Array<OneD, NekDouble> > > &derivativesO1,
               Array<OneD, Array<OneD, Array<OneD, NekDouble> > > &viscousTensor)
     {
-        int i, j, k;
+        int j, k;
         int nVariables = m_fields.num_elements();
         int nPts       = physfield[0].num_elements();
 
@@ -992,15 +992,14 @@ namespace Nektar
         Array<OneD, NekDouble > STx(nPts, 0.0);
         Array<OneD, NekDouble > STy(nPts, 0.0);
         Array<OneD, NekDouble > STz(nPts, 0.0);
+
         // Building the viscous flux vector
-        //if (i == 0)
-        //{
-            // Viscous flux vector for the rho equation
-            for (k = 0; k < m_spacedim; ++k)
-            {
-                Vmath::Zero(nPts, viscousTensor[k][i], 1);
-            }
-            //}
+
+        // Viscous flux vector for the rho equation
+        for (k = 0; k < m_spacedim; ++k)
+        {
+            Vmath::Zero(nPts, viscousTensor[k][0], 1);
+        }
 
         if (m_spacedim == 1)
         {

solvers/CompressibleFlowSolver/Tests/Couette_FRHU_LFRHU_SEM.tst

@@ -8,7 +8,7 @@
     </files>
     <metrics>
         <metric type="L2" id="1">
-            <value variable="rho" tolerance="1e-12">0.0889272</value>
+            <value variable="rho" tolerance="1e-8">0.0889271</value>
             <value variable="rhou" tolerance="1e-12">62.1128</value>
             <value variable="rhov" tolerance="1e-8">0.175956</value>
             <value variable="E" tolerance="1e-12">4905.04</value>