Ramin,

You should first check the quality of your mesh in this region and make sure the mesh is in good condition (no skewness).

If the mesh if fine, there are many possible explanations related to the numerical aspects.

Best regards

Thank you for your answer, in this area mesh is structured and not skewed.

I used sliding mesh, MRF, and Dynamic Mesh, but this problem remains with different Max values of T, but higher than inlet!

Even I simulate the turbine without this gap, and still T increases to higher values than inlet inside the turbine this time.

I appreciate any ideas about this

What about the wall boundary conditions ? What BC do you use : fixed temperature, heat flux?

It looks like you are generating a heat that can’t be dissipated through the wall, and keep on accumulating causing temperature increase.

If yes try convective heat transfer as BC at walls.

Good luck.

walls are assumed adiabatic, zero heat flux is the BC.

I am wondering which term in energy equation is making this energy production. flow is continuously blows from inlet toward the outlet, how energy remains in the domain even using zero heat flux in walls!