The unsteady behavior of fluid flow such as pressure variation and fluctuation in a hydraulic turbine may lead to operational instability. Such dynamic behaviors effect the performance of rotating machines, which may reduce life span and even have impact on the overall safety of the turbine. The objectives of this study are to analyze the flow characteristics and to undertake a transient Fast Fourier Transform (FFT) analysis of a model turbine to investigate the stability of operational conditions. Flow analysis was conducted by changing the number of revolutions to 100, 200, 300, and 350 rpm. Reynolds-averaged Navier Stokes equations were discretized by the finite volume. method and a two equations shear stress transport model was used to account for the three dimensionality of unsteady flows. FFT analysis was performed by monitoring dynamic pressure fluctuation on the rotor and casing. Results revealed that as the number of revolutions increased, the flow gradually became more stable as it approached the rated rotation speed of 350 rpm. Also an experiment was conducted to verify the numerical performance and a good tendency of the results was achieved.