[FEM] fine-tune flow examples

- use a more sensible velocity distribution
- change inlet temperature for 2 examples

- also change step size for nonlinear iterations for more convenience for practical usage

src/Mod/Fem/femsolver/elmer/equations/nonlinear.py

@@ -76,7 +76,7 @@ class Proxy(linear.Proxy):
             )
         )
 
-        obj.NonlinearIterations = (500, 1, int(1e6), 50)
+        obj.NonlinearIterations = (500, 1, int(1e6), 10)
         obj.NonlinearNewtonAfterIterations = (3, 1, 100, 1)
         # for small numbers we must set an expression because we don't have a UI,
         # the user has to view and edit the tolerance via the property editor and