Abstract：The pressure fluctuation in the flow passage of both impeller and casing is addressed on design condition． The initial
conditions for the unsteady turbulent simulation are resulted from the steady calculations， and the three dimensional unsteady turbulent
simulation concerning the rotor·stator interaction is executed by a Navier．Stoke solver embedded with k—s turbulence model and with
appropriate moving interface boundary conditions．Detecting points are distributed in the flow passage in diferent radial and
circumferential positions to capture the static pressure fluctuation character for one cycle of the impeller．The time—domain spectrums
show that the static pressure curves are periodic and have five peaks and five valleys．W ith the radius increasing，the pressure fluctuation
peak-to-peak values in the impeller are increasing，and reach the maximum value on the interface． In the casing flow passage，those
values are about 7％ of local static pressure except some ones near the tongue．The values become decreasingly in the difuser pipe．The
frequency spectrums transformed by fast Fourier transform (FFT)show that the dominant frequency is approximate with the blade
passing frequency,and the pressur e fluctu ations in impeller passage have high frequency content while those in casing ones have no
such jnformation．
