Sir, as you have mentioned to specify Supersonic Initial Gauge Pressure = 0 (if really no supersonic flow coming from there)
Sir, this problem is similar to like Nozzle Chamber at given stagnation pressure and temperature. So I don't think so there will be any flow at nozzle Inlet, because of pressure difference created by Chamber Pressure and Ambient Pressure the flow will pass through nozzle.
Sir, my doubt is why 0 instead of specifying Supersonic Initial Gauge Pressure = Po.
As static pressure is same as stagnation pressure at nozzle chamber inlet.
Or is it because as there is no supersonic flow at nozzle chamber inlet, hence specify Supersonic Initial Gauge Pressure = 0.
Sir, I hope my understanding is correct.