multiphasebasemodel: do not set a default flux module

examples/finger_immiscible_vcfv.cpp

@@ -27,9 +27,11 @@
  */
 #include "config.h"
 
-#include <opm/models/utils/start.hh>
-#include <opm/models/immiscible/immisciblemodel.hh>
+#include <opm/models/common/darcyfluxmodule.hh>
 #include <opm/models/discretization/vcfv/vcfvdiscretization.hh>
+#include <opm/models/immiscible/immisciblemodel.hh>
+#include <opm/models/utils/start.hh>
+
 #include <opm/simulators/linalg/parallelbicgstabbackend.hh>
 
 #include "problems/fingerproblem.hh"
@@ -38,10 +40,20 @@ namespace Opm::Properties {
 
 // Create new type tags
 namespace TTag {
-struct FingerProblemVcfv { using InheritsFrom = std::tuple<FingerBaseProblem, ImmiscibleTwoPhaseModel>; };
+
+struct FingerProblemVcfv
+{ using InheritsFrom = std::tuple<FingerBaseProblem, ImmiscibleTwoPhaseModel>; };
+
 } // end namespace TTag
+
 template<class TypeTag>
-struct SpatialDiscretizationSplice<TypeTag, TTag::FingerProblemVcfv> { using type = TTag::VcfvDiscretization; };
+struct SpatialDiscretizationSplice<TypeTag, TTag::FingerProblemVcfv>
+{ using type = TTag::VcfvDiscretization; };
+
+//! Use the Darcy relation to determine the phase velocity
+template<class TypeTag>
+struct FluxModule<TypeTag, TTag::FingerProblemVcfv>
+{ using type = DarcyFluxModule<TypeTag>; };
 
 } // namespace Opm::Properties