chore(bemt): add warning for coax solvers

src/solvers/bemt.m

@@ -42,7 +42,13 @@ function bemt(OpRot, Mod)
     for i = 2:length(OpRot)
 
         % Solves BEMT equations for the rotor using the true distribution of external velocity
-        OpRot(i).ElPerf.updateupstreamvel(OpRot(i - 1));
+        if strcmpi(Mod.solver, 'indvel')
+            OpRot(i).ElPerf.updateupstreamvel(OpRot(i - 1));
+        else
+            warning('Rotare:Solvers:CoaxialNotSupported', ...
+                    ['Coaxial rotors are only supported with indvel at the moment.'...
+                     'Additional rotors are calculated as if they were isolated.\n']);
+        end
         bemtsinglerot(OpRot(i), Mod);
 
     end