fix: switch OSWEC solver from SPARSE_QR to GMRES to prevent divergence

SPARSE_QR causes the OSWEC model to blow up.
GMRES is stable for all OSWEC cases (decay and regular waves).

Author: dav-og

demos/oswec/demo_oswec_decay.cpp

@@ -88,7 +88,7 @@ int main(int argc, char* argv[]) {
     system.SetGravitationalAcceleration(ChVector3d(0.0, 0.0, -9.81));
     double timestep = 0.03;
     // system.SetTimestepperType(ChTimestepper::Type::HHT);
-    system.SetSolverType(ChSolver::Type::SPARSE_QR);
+    system.SetSolverType(ChSolver::Type::GMRES);
     // system.GetSolver()->AsIterative()->SetMaxIterations(300);  // the higher, the easier to keep the constraints
     // satisfied.
     ChRealtimeStepTimer realtime_timer;

demos/oswec/demo_oswec_reg_waves.cpp

@@ -95,7 +95,7 @@ int main(int argc, char* argv[]) {
         system.SetGravitationalAcceleration(ChVector3d(0.0, 0.0, -9.81));
         double timestep = 0.03;
         // system.SetTimestepperType(ChTimestepper::Type::HHT);
-        system.SetSolverType(ChSolver::Type::SPARSE_QR);
+        system.SetSolverType(ChSolver::Type::GMRES);
         // system.GetSolver()->AsIterative()->SetMaxIterations(300);
         ChRealtimeStepTimer realtime_timer;
         double simulationDuration = 1000.0;

tests/regression/oswec/test_oswec_decay.cpp

@@ -65,7 +65,7 @@ int main(int argc, char* argv[]) {
 
     system.SetGravitationalAcceleration(ChVector3d(0.0, 0.0, -9.81));
     double timestep = 0.03;
-    system.SetSolverType(ChSolver::Type::SPARSE_QR);
+    system.SetSolverType(ChSolver::Type::GMRES);
     double simulationDuration = 400.0;
 
     // Output timeseries

tests/regression/oswec/test_oswec_reg_waves.cpp

@@ -37,7 +37,7 @@ int main(int argc, char* argv[]) {
 
         system.SetGravitationalAcceleration(ChVector3d(0.0, 0.0, -9.81));
         double timestep = 0.03;
-        system.SetSolverType(ChSolver::Type::SPARSE_QR);
+        system.SetSolverType(ChSolver::Type::GMRES);
         double simulationDuration = 240.0;
 
         // Output timeseries