I recommend you to use the turboworkflow in ansys fluent . I am attaching a link explaining the turbo workflow for the axial compressor which is similar to axial turbine .Please go through that. It can simplify your analysis.
Also there are courses in learning hub . Please go to ALH site ->Under fluids choose turbomachinery and then choose ansys fluent rotating machinery modelling and download it. In that there is a tutorial related to axial turbine.
At the moment for transient analysis in turboworkflow there is an example please refer this user guide link.
I hope this helps you in your simulation.