Self-excited shock oscillation in transonic diffuser flows. 2nd report . Spectral distribution and peak frequency of oscillation; Sen'onsoku diffuser nagare ni okeru shogekiha no jirei shindo. 2. shindo no spekutoru bunpu to peak shuhasu

Concerning the self-excited shock oscillation in a transonic diffuser flow, the response of a normal shock wave to a 'white' pressure disturbance, that is, a small pressure disturbance having the same power spectral density over every frequency, is analyzed by solving the equation representing shock displacement due to the disturbance. According to the present analysis, the spectral density distribution and peak frequency of the shock oscillation depend on Mach number just upstream of the shock wave and a non-dimensional parameter determined from the diffuser geometry at the time-mean shock location. The shock displacement power spectral density distributions obtained by the analysis agree very well with those measured in our experiment. A non-dimensional relationship between the peak frequency of the shock oscillation and diffuser geometry at the shock location, Eq. (18), is obtained, and this equation agrees well with the present and previous experimental results. (author)