# Vacuum force factors (vacuum created by a "flow through" liquid)

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• Ralphamale01
In summary, the surface area of the container does not affect the amount of vacuum developed. The depth of the liquid in the container is the most important factor.

#### Ralphamale01

TL;DR Summary
How is vacuum related to surface area?
Greetings all,

I'm new here and hope I'm asking this in the correct thread. So, the question is; where you have a vacuum created by a "flow through" liquid witin a large diameter container exerting suction force upon a smaller diameter input tube submerged in a liquid, does the surface area of the container determine how much vacuum is developed, or is the depth (weight) of liquid in container an equal, greater or minimal factor? Please see attached sketch. Thank in advance for any help.

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Welcome to PF.

A vacuum is limited by atmospheric pressure, and the vapour pressure of the liquid.

The area of the wall is NOT important, because pressure is a force per area.

The most important thing is the depth, density and hydrostatic pressure. That is the force of liquid per unit area, which increases with depth.
https://en.wikipedia.org/wiki/Hydrostatics#Pressure_in_fluids_at_rest

Baluncore said:
Welcome to PF.

A vacuum is limited by atmospheric pressure, and the vapour pressure of the liquid.

The area of the wall is NOT important, because pressure is a force per area.

The most important thing is the depth, density and hydrostatic pressure. That is the force of liquid per unit area, which increases with depth.
https://en.wikipedia.org/wiki/Hydrostatics#Pressure_in_fluids_at_rest
Understood, Thank You!

In hydraulics, life is very easy because the pressure varies within the liquid simply in proportion to the depth.
So in your case, as liquid flows out the tank, the air layer gets expanded, its pressure reduces and water is "sucked" up the tube. This can continue until the depth of water in the pipe matches the depth of water in the tank.
The pressure in the air pocket will have reduced by the depth x density of liquid, so now the atmospheric pressure is just enough to stop the liquid pushing out of the tank and to support the liquid in the tube.

As an interesting (IMO) sidenote, if there had not been any air pocket at all - the pipe and tank had started completely filled with liquid - then the liquid would not drain out of the tank at the bottom, rather the liquid would flow down the pipe. Air would enter the tank from below until it had filled the horizontal pipe and enough of the vertical pipe to equalise the depths in pipe and tank.

Merlin3189 said:
In hydraulics, life is very easy because the pressure varies within the liquid simply in proportion to the depth.
So in your case, as liquid flows out the tank, the air layer gets expanded, its pressure reduces and water is "sucked" up the tube. This can continue until the depth of water in the pipe matches the depth of water in the tank.
The pressure in the air pocket will have reduced by the depth x density of liquid, so now the atmospheric pressure is just enough to stop the liquid pushing out of the tank and to support the liquid in the tube.

As an interesting (IMO) sidenote, if there had not been any air pocket at all - the pipe and tank had started completely filled with liquid - then the liquid would not drain out of the tank at the bottom, rather the liquid would flow down the pipe. Air would enter the tank from below until it had filled the horizontal pipe and enough of the vertical pipe to equalise the depths in pipe and tank.

## 1. How is vacuum force created by a "flow through" liquid?

Vacuum force is created by the movement of a liquid through a tube or channel. As the liquid flows through the tube, it creates a pressure differential between the inlet and outlet ends. This pressure differential creates a vacuum force that can be utilized for various purposes.

## 2. What are some common applications for vacuum force created by a "flow through" liquid?

Vacuum force created by a "flow through" liquid can be used in a variety of applications, including water filtration, irrigation systems, and vacuum pumps. It can also be used in industrial processes, such as distillation and chemical reactions.

## 3. How does the viscosity of the liquid affect vacuum force?

The viscosity of the liquid can have a significant impact on the vacuum force created by a "flow through" liquid. Higher viscosity liquids, such as oils, will create a stronger vacuum force compared to lower viscosity liquids, such as water.

## 4. Is there a limit to the vacuum force that can be created by a "flow through" liquid?

Yes, there is a limit to the vacuum force that can be created by a "flow through" liquid. This is determined by factors such as the rate of flow, the viscosity of the liquid, and the geometry of the tube or channel through which the liquid is flowing.

## 5. Can vacuum force be used to create a vacuum in a closed system?

Yes, vacuum force created by a "flow through" liquid can be used to create a vacuum in a closed system. This can be achieved by designing the system in such a way that the liquid is continuously flowing through the system, creating a pressure differential and a vacuum force.