Rotating blades of steam turbines are subjected to unsteady forces due to the presence of both wake and potential field from the adjacent stationary blade rows. The combined effects of both axial gap and blade count ratio on the unsteady forces have been demonstrated on a steam turbine stage. This study shows their effects on the forced response. Further investigations show their effects on stimulus, aero damping and frequency shift. This study uses a one-way coupling dynamic stress prediction tool, which integrates an in-house Computational Fluid Dynamic solver TF3D-VIB with a commercial Finite Element solver ABAQUS.Copyright © 2013 by Alstom Technology