The effect of pressure gradient across dissimilar fluids

AI Thread Summary
A strong negative pressure can indeed pull gas through a liquid, depending on the pressure gradient established. In the described U-shaped pipe scenario, creating a vacuum at the open end would lower the water level on the closed end, potentially allowing air to bubble out. The air may start to flow through the water even before the water level drops below the bottom of the U, as the pressure difference initiates movement. In applications like injection molding, a low-pressure area above the fluid can facilitate fluid movement into recessed areas of a mold over time. Understanding these dynamics is crucial for optimizing vacuum systems in various industrial processes.
Dane P
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So my question is - would a strong enough negative pressure be able to pull a gas through a liquid? I can draw a diagram if anyone needs it but I'm trying to figure out what would happen in the following situation. Imagine you had a solid pipe that formed a large U shape with one end sealed, you fill the pipe halfway with water so that the bottom of both legs of the U are filled with water and the tops contain air. I understand that creating a vacuum at the open end would cause the water level on the closed end to drop, but would it have to drop to the point where the water level goes below the bottom of the U for the air to bubble out and be replaced by water rapidly or would the air start slowly flowing through the water at a slow rate as soon as the pressure gradient is created?

The real application of this I'm trying to understand would be similar to how they use vacuum systems in injection molding. Imagine you were trying to make something with a mold that looked like a solid steel sombrero in a box. If you filled the base of the mold with your fluid, created a low pressure area above the fluid, and the fluid had a pathway into the high center part of the mold, with enough time would the recessed center area eventually fill with the fluid? Obviously in real life you'd turn the mold upside down and fill it, but I'm just trying to conceptualize what would happen in this situation.
 
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Dane P said:
So my question is - would a strong enough negative pressure be able to pull a gas through a liquid? I can draw a diagram if anyone needs it
I need it.
 
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