Under what circumstances would there be an increase in pressure in a divergent nozzle ?

Under what circumstances would there be an increase in pressure in a divergent nozzle ?
Ans. For subsonic flow at inlet section of a diffuser a lower velocity and higher pressure will exist at the exit section. For supersonic isentropic flow at the inlet section a higher velocity and lower pressure will exist at the exit but if a shock wave occurs in the diffuser then a higher pressure will exist at the exit.