Based on obtained frequency, 1/8 cycle time is 4.464e-04. so I set up time 1/40 cycle to 1000 steps to see 25 cycle. The measured pressure at nozzle outlet is 130000 Pa (1.3 atm).
Experimentally, shocks are not appeared in oscillator or outlet.
For my conditions, NPR 2.2 and 13m/s is obtained at chamber.
NPR 4.0 ( about 400 kPa) also has results that don’t reach the speed of sound at nozzle outlet.
So I’ll try to analyze it slowly from NPR 2.2 with ansys fluent(Fluid flow)