# Suction Pressure at different orifices

## Main Question or Discussion Point

Hello engineers,
I am struggling with this seemingly simple problem and I was hoping to get some directions. Please look at the attached figure. I have a small chamber with a tube (radius=3mm) that is connected to a vacuum pump. The pump operates at -600 mmHg. The chamber is filled with air at room temperature. The other surface of the chamber has 3 orifices with diameters 2, 4 and 6 mm. Assume that there is a a porous membrane on the other side of the chamber. Now:
What is the pressure at each of the orifices? Since pressure is force per unit area, I would think that the pressure (force per unit area) experienced by the porous membrane at each orifice will be the same. Is that right? Will it be -600 mmHg. Or will it vary depending on the orifice size?

Further, if the orifices are replaced by tubes with diameters corresponding to the respective orifices they replaced, what (if anything ) will change? I think we can perhaps calculate the air pressure and velocity in each pipe using Bernoulli equation. For pipe with 2 mm diameter, the pressure will smaller.
I appreciate any response in advance.

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