Header warning

Include a header warning explaining the purpose and how to use this testcase.

Author: suargi

TestCases/turbulence_models/sa/rae2822/turb_SA_NEG_RAE2822.cfg

@@ -1,3 +1,19 @@
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%                                                                              %
+%                                  WARNING                                     %
+%                      This regression test will diverge!                      %
+%									       %
+% This test case is only meant to trigger the negative part of the SA model,   %
+% to check the integrity of the commits. It is inadvisable to use it as an     %
+% starting point for tutorials.						       %
+% The rae2822 airfoil is a simple (fast) case. A high angle of attack is being %
+% used in order to force the negative part of the SA in a reasonable amount of %
+% iterations. With the current configuration, e.g., convective scheme, CFL     %
+% number, etc, the solution is not stable and diverges after some iterations,  %
+% around 15. Therefore, this regression test shall only run for iter < 15.     %
+%                                                                              %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
 % ------------- DIRECT, ADJOINT, AND LINEARIZED PROBLEM DEFINITION ------------%
 %
 % Physical governing equations