Pass velocityLB in both cases via config file.

apps/gpu/DrivenCavity/DrivenCavity.cpp

@@ -74,12 +74,13 @@ int main(int argc, char* argv[])
         const real length = 1.0;
         const real reynoldsNumber = 1000.0;
         const real velocity = 1.0;
-        real velocityLB = 0.05; // LB units
         const uint numberOfNodesX = 64;
 
         const uint timeStepOut = 1000;
         const uint timeStepEnd = 10000;
 
+        real velocityLB = 0.05; // LB units
+
         vf::basics::ConfigurationFile config = vf::basics::loadConfig(argc, argv);
 
         bool refine = false;

apps/gpu/DrivenCavity/drivencavity_2level.cfg

@@ -2,3 +2,5 @@
 refine = true
 
 output_path = ./output/DrivenCavity
+
+velocityLB = 0.05
\ No newline at end of file