The effect of pressure gradient across dissimilar fluids

In summary, the conversation discusses the potential for a strong negative pressure to pull a gas through a liquid. The speaker uses the example of a U-shaped pipe filled with water and air to illustrate their question. Additionally, they mention the application of this concept in injection molding and question whether a recessed center area would eventually fill with fluid if a low pressure area was created above it.
  • #1
Dane P
4
0
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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  • #2
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.
 

1. What is a pressure gradient?

A pressure gradient is the change in pressure between two points in a fluid. It is usually measured in units of pressure per unit distance, such as psi/in or Pa/m.

2. How does pressure gradient affect different fluids?

The effect of pressure gradient on different fluids depends on their physical properties, such as density and viscosity. In general, a larger pressure gradient will result in a higher velocity of flow for less viscous fluids, while more viscous fluids will experience a smaller velocity change.

3. Can pressure gradient cause mixing between dissimilar fluids?

Yes, pressure gradient can cause mixing between dissimilar fluids. If the pressure gradient is high enough, it can overcome the differences in density and viscosity between the fluids and cause them to mix together.

4. How is pressure gradient across dissimilar fluids measured?

Pressure gradient can be measured using a variety of instruments, such as a manometer or a pressure transducer. The pressure difference between the two points in the fluid can then be calculated using the measured values.

5. What are some real-world applications of studying the effect of pressure gradient across dissimilar fluids?

Studying the effect of pressure gradient across dissimilar fluids is important in many fields, including chemical and process engineering, fluid dynamics, and environmental science. It can help us understand and predict how fluids will behave in various systems, such as pipelines, pumps, and mixing tanks. It is also relevant in natural phenomena, such as ocean currents and weather patterns.

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