Fluid Dynamics: Pressure / Opening a hatch underwater

In summary, the conversation discusses the calculation of the force needed to open a hatch on a submarine. The hatch has a pressure of 2 atm on the outside and 1 atm on the inside. There is a debate about whether the pressure inside the vessel should be taken into account when calculating the force needed to open the hatch. The correct formula is determined to be F = (Po - Pi)S, where Po is the outside pressure and Pi is the inside pressure. It is also mentioned that the conversation is a year old.
  • #1
Farzan
15
0
Let's say that you're deep under the surface of the water in a submarine type thing.

There is a hatch on the top.

Let's say that the absolute pressure on the top of the hatch was calculated to be 2 atm.

Inside the vessel, the pressure is only 1 atm.

Someone is inside the vessel and the force needed to open the hatch must be calculated.

Do you need to take into account the pressure inside the vessel?

P = F/A

Do you plug in 2 atm, or 1 atm?

My physics teacher said that you only look at the pressure on the outside, but he does not remember why.
 
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  • #2
Farzan said:
My physics teacher said that you only look at the pressure on the outside, but he does not remember why.

Then why is he teaching physics? :confused:
I know pretty much nothing about anything, but I do know that the force required to open the hatch is based upon the ratio of interior/exterior pressure.
 
  • #3
Danger said:
... the force required to open the hatch is based upon the ratio of interior/exterior pressure.

Not the ratio. The difference: F= (Po-Pi)S
 
  • #4
Good catch. I have to start being more accurate in my terminology. After a few beers I get sloppy.
 
  • #5
Wouldn't you take the difference in pressure? You have 2 atm pushing in and 1 atm pushing out, requiring you to push through 1 atm to open the hatch, right?
 
  • #6
Deathwing said:
Wouldn't you take the difference in pressure? You have 2 atm pushing in and 1 atm pushing out, requiring you to push through 1 atm to open the hatch, right?
Realize that you are responding to a thread that's been dormant for almost a year. In any case, the point about needing the difference in pressure was made by lpfr in post #3.
 

1. What is fluid dynamics?

Fluid dynamics is the study of how fluids (liquids and gases) behave when they are in motion. It involves understanding the forces and pressures that act on fluids, and how they affect the motion and behavior of the fluid.

2. How does pressure relate to fluid dynamics?

Pressure is a key concept in fluid dynamics. It is the force per unit area that a fluid exerts on its surroundings. In fluid dynamics, pressure is used to describe the forces that cause fluids to flow or move.

3. How does opening a hatch underwater affect fluid dynamics?

Opening a hatch underwater can significantly affect fluid dynamics. When a hatch is opened, it creates an opening or a hole in the fluid, causing changes in pressure and flow patterns. This can lead to the movement of the surrounding fluid and can also affect the stability of the object or vessel the hatch is attached to.

4. What happens to pressure when a hatch is opened underwater?

When a hatch is opened underwater, the pressure inside the hatch will equalize with the pressure outside. This can cause a sudden change in pressure, which can lead to turbulence and changes in the flow of the fluid. It can also create a force that can push or pull objects in the fluid.

5. Why is it important to understand fluid dynamics when opening a hatch underwater?

Understanding fluid dynamics is crucial when opening a hatch underwater because it can help predict the effects of opening the hatch. It can also help in designing hatches that are more efficient and less likely to cause turbulence or instability in the surrounding fluid. Additionally, understanding fluid dynamics can help in ensuring the safety of divers and equipment when opening a hatch underwater.

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