relief valve outlet pipe - velocity

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We are modeling a relief valve 6" outlet pipe/elbow 6' long discharging to atmosphere. We have modeled the relief valve with a converging nozzle where the throat area has been adjusted to give the capacity required for the set of inlet conditions.

All of the outlet parameters (outlet pressure, temperature, and velocity at the elbow) look reasonable except that the outlet velocity exceeds Mach 1 (1.24) which it can't.

While the outlet velocity is not one of the outputs that we are concerned with there are a few questions:

1.Is it reasonable to just ignore this and accept all of the rest of the outputs?
2. Is this a limitation of the program that can't deal with shock waves?
3. Is there something that can be done to "tweak" the model to correct this anomaly?

I've attached a plot for reference.

Thanks,

 

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forgot to attach