fix: Fix bug in stability test bypass

.integrated_tests.yaml

@@ -1,6 +1,6 @@
 baselines:
   bucket: geosx
-  baseline: integratedTests/baseline_integratedTests-pr3224-13023-0334b63
+  baseline: integratedTests/baseline_integratedTests-pr3783-13079-916d2a0
 
 allow_fail:
   all: ''

BASELINE_NOTES.md

@@ -6,6 +6,10 @@ This file is designed to track changes to the integrated test baselines.
 Any developer who updates the baseline ID in the .integrated_tests.yaml file is expected to create an entry in this file with the pull request number, date, and their justification for rebaselining.
 These notes should be in reverse-chronological order, and use the following time format: (YYYY-MM-DD).
 
+PR #3783 (2025-08-22) <https://storage.googleapis.com/geosx/integratedTests/baseline_integratedTests-pr3783-13079-916d2a0.tar.gz>
+=====================
+Update bug in single phase flash handling
+
 PR #3224 (2025-08-22) <https://storage.googleapis.com/geosx/integratedTests/baseline_integratedTests-pr3224-13023-0334b63.tar.gz>
 =====================
 Add Taper boundary conditions inside second-order wave solvers

src/coreComponents/constitutive/fluid/multifluid/compositional/models/NegativeTwoPhaseFlashModel.hpp

@@ -82,9 +82,13 @@ class NegativeTwoPhaseFlashModelUpdate final : public FunctionBaseUpdate
 
     StackArray< real64, 1, maxNumComps > incipientComposition( m_numComponents );
 
+    integer pureComponent = -1;
+    integer almostPureComponent = -1;
+    checkPureMixture( m_numComponents, compFraction, pureComponent, almostPureComponent );
+
     // Check if k-Values need to be initialised
     auto kVapourLiquid = kValues[0];
-    bool const needInitialisation = hasZero( m_numComponents, kVapourLiquid.toSliceConst() );
+    bool const needInitialisation = (pureComponent < 0) && hasZero( m_numComponents, kVapourLiquid.toSliceConst() );
     if( needInitialisation )
     {
       if( m_flashData.liquidEos == EquationOfStateType::SoreideWhitson )
@@ -111,14 +115,10 @@ class NegativeTwoPhaseFlashModelUpdate final : public FunctionBaseUpdate
     integer const stabilityIterations = m_discreteFlashParameters[FlashParameters::STABILITY_MAX_ITERATIONS];
 
     bool unstableMixture = false;
-    bool stabilityStatus = false;
+    bool stabilityStatus = (0 <= pureComponent);
     EquationOfStateType incipientEquationOfState = m_flashData.liquidEos;
 
-    integer pureComponent = -1;
-    integer almostPureComponent = -1;
-    checkPureMixture( m_numComponents, compFraction, pureComponent, almostPureComponent );
-
-    if( 0 < stabilityIterations || needInitialisation )
+    if( ((pureComponent < 0) && (0 < stabilityIterations)) || needInitialisation )
     {
       stabilityStatus = StabilityTest::compute( m_numComponents,
                                                 pressure,
@@ -133,6 +133,13 @@ class NegativeTwoPhaseFlashModelUpdate final : public FunctionBaseUpdate
                                                 incipientEquationOfState,
                                                 incipientComposition.toSlice() );
     }
+    else
+    {
+      for( integer ic = 0; ic < m_numComponents; ++ic )
+      {
+        incipientComposition[ic] = compFraction[ic];
+      }
+    }
 
     // Pure mixtures are always stable
     if( 0 <= pureComponent )