# Urgent help needed: flow through orifice

1. May 3, 2010

### sovietjet

Hi. I am looking for a relation or coefficient which describes the pressure loss of a flow through an orifice. Now I know what this is for a normal flat plate orifice for water. What I need is the appropriate coefficients for an orifice plate at an angle both for water(incompressible) and air(compressible). Assuming choked flow at the orifice for the air. Here's a diagram of what I'm talking about.

As you can see the flow approaches the orifices like that. The thin plates are at an angle of 45 degrees. After it passes through, both streams mix. I need to figure out the pressure difference before and after the orifices. I have broken it down into the following.

K = K1 + K2 + K3

K1 = K loss coefficient for a flow through an orifice. I know this already.
K2 = K loss coefficient of the projected area. Since it is at 45 degree the "projected" area is smaller than the actual area of the orifice. In other words what the flow "sees" as it approaches is a smaller hole than what is in fact there. There must be some type of coefficient for this.
K3 = K loss coefficient for the turbulent mixing that occurs after the flow passes through. Any links? Estimates?

Once I get this total K I can get an estimate for the pressure drop. Again, I only need estimates. I know that K1 is about 0.63 for a typical sharp edged orifice. The orifices are circles. The two upstream conditions are:

1) water, incompressible at some flow rate(not low Reynolds number)
2) Air, flow at orifice is choked.

Any ideas?
Thanks