# Choking in a Circular Orifice Plate in a pipe

1. Jan 21, 2009

### boka33

The equation I have for velocity through a circular orifice plater is as follows:

$$Ud = \frac{Yi\timesC}{\sqrt{(1-(d/D)^4)}}\sqrt{\frac{(2\times(P_{2}-P_{1})}{\rho}}$$

To my understanding, flow becomes choked when this velocity exceeds a Mach number of 1, and is no longer sub-sonic.

Intuitively, decreasing orifice diamter would increase the likelyhood of choke (at least in my mind), but this does not seem to be the case.

If d/D is decreased, the denominator becomes larger, and the velocity becomes smaller, in turn yielding a smaller mach number.

Can anyone explain this so that it make more intuitive sense to me, or tell me if my thouhgt process is off.

Thanks alot