Normal shocks form in pipe outlets?
Normal shocks form in pipe outlets?
(OP)
Hello all,
How do you explain that downstream from a regulator you have a pressure of several hundred psig and further downstream (some 200 ft) the pipe is discharging to the atmosphere, hence the pressure is 0 psig.
Is there a normal shock standing at the pipe outlet to the atmosphere?





RE: Normal shocks form in pipe outlets?
However, for "several hunderd" psi drop across a 200 ft pipe, you will probably have choked flow at the outlet.
RE: Normal shocks form in pipe outlets?
CJKruger, thanks for the reply.
The pressure ratio certainly indicates that the flow is choked. However, there is an even larger pressure drop across the regulator (from 2kpsig to 150psig) which would indicate choking as well.
In other words, I have a regulator in which the pressure drops from 2kpsig to 150psig, and then (200 ft downstream) an opening to atmosphere where the pressure drops to 0 psig. So, the flow is choked in two locations?
RE: Normal shocks form in pipe outlets?
From what you describe, it sounds very much like you have choked flow at the outlet, which implies a standing wave immediately upstream of the outlet.
David
RE: Normal shocks form in pipe outlets?
David, thanks for the reply.
The flow path through a pressure regulator is designed to avoid (not prevent) choked flow within the regulator
Do you know of any publicly available reference that states this? Maybe a manufacturer's catalog, or some instrumentation book?
Thanks,
RE: Normal shocks form in pipe outlets?
David
RE: Normal shocks form in pipe outlets?
To reduce noise, vendors use things like "whisper trim" and staged letdown. I have not had good success with the whisper trim type installations, as they plug up.