radial inflow turbine rotor periodicity problem
 

hi, i've modelled a flow passage of a radial inflow turbine consisting 15 blades.for modelling purpose i made use of the periodicity of the flow and modelled a single passage.however when i displayed the result by taking 0.5 constant grid spanwise location and displayed the 360 degrees view, the default number of repeats was 17 which is not consistent with my model.any suggestion of what am i doing wrong? i've already checked and rechecked my model in gambit.