[test][navierstokes] Add parameters in input file to improve documentation of...

[test][navierstokes] Add parameters in input file to improve documentation of the numeric epsilon feature

test/freeflow/navierstokes/test_channel_stokes.input

@@ -18,3 +18,15 @@ MaxRelativeShift = 1e-8
 [Vtk]
 AddVelocity = true
 WriteFaceData = false
+
+
+[Assembly]
+NumericDifference.BaseEpsilon =  1e-8
+
+# This test does actually not require setting the primary variable magnitues.
+# This rather serves as a demonstration of how to use the feature.
+[CellCenter.Assembly]
+NumericDifference.PriVarMagnitude = 1e5 # pressure is in the order of 1e5
+
+[Face.Assembly]
+NumericDifference.PriVarMagnitude = 1 # velocity is in the order of 1