Dear Hooman,
Your AeroDyn v15.04 input file looks fine. However, to use AeroDyn v15.04 with FAST v8, you must recompile FAST v8 with the new AeroDyn v15.04 source files. See e.g. the following forum topic for more information: Compile Aerodyn 15.04 source files in FAST - #8 by Jason.Jonkman.
Best regards,