How does a faucet use the Venturi principle

In summary, the conversation discusses the relationship between the velocity and flow rate of water in a faucet, specifically when there is a change in nozzle area or pressure. It is noted that the velocity and flow rate remain constant as long as the pressure in the main supply pipe is constant. It is also mentioned that the velocity may increase at the valve restriction, but it is dampened by the return to normal pressure levels. The conversation also brings up the principle of continuity in fluid dynamics and how changes in velocity and flow rate are dependent on external forces or changes in mass. A simple formula for calculating the velocity of water through a nozzle based on pressure drop is also requested.
  • #1
TheWonderer1
88
1
I've noticed that a slight opening of the faucet releases less water which makes sense intuitively but I don't notice an increase in velocity. Since a slight opening in the stopper would be a convergence in cross sectional area. Am I missing something? I read about resistance affect but still thought I would ask the question.
 
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  • #2
Good question. But remember that the velocity at the spigot outlet should be compared to the velocity in the supply pipe, which IS much slower. It should not be compared to the velocity of some other valve setting, where all velocities are higher or lower.
 
  • #3
FactChecker said:
Good question. But remember that the velocity at the spigot outlet should be compared to the velocity in the supply pipe, which IS much slower. It should not be compared to the velocity of some other valve setting, where all velocities are higher or lower.
So I guess it's like I suspected? If the supply pipe is much slower than the velocity at the spigot outlet? I would just be interested bc I'm trying to learn more about fluid dynamics.
 
  • #4
TheWonderer1 said:
I've noticed that a slight opening of the faucet releases less water which makes sense intuitively but I don't notice an increase in velocity. Since a slight opening in the stopper would be a convergence in cross sectional area. Am I missing something?
WHERE is the velocity higher in a Venturi tube?
 
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  • #5
TheWonderer1 said:
So I guess it's like I suspected? If the supply pipe is much slower than the velocity at the spigot outlet? I would just be interested bc I'm trying to learn more about fluid dynamics.
I should have said the velocity within the valve restriction. Once the water gets beyond that and into the larger spigot pipe, it will slow down again.
 
  • #6
russ_watters said:
WHERE is the velocity higher in a Venturi tube?
At the restriction, I believe at the vena contracta to be exact is where it has the least diameter and max velocity. I see that I was over thinking it.
 
  • #7
TheWonderer1 said:
At the restriction, I believe at the vena contracta to be exact is where it has the least diameter and max velocity. I see that I was over thinking it.
Right, so in a faucet, the opening is full size and the restriction is at the valve...which you can't see, but might be able to hear.
 
  • #8
In most domestic water supplies the pressure in the primary mains does not usually vary much in the short term .

Pressure may vary more within a connected property depending on how much water is being used but assume that your faucet is the only one that is turned on at the time of your experiment .

So you effectively have a constant pressure water source and a variable area nozzle . What conclusion can you reach about the flow velocity and the flow rate of water through the nozzle as the nozzle area is varied ?
 
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  • #9
It's my understanding at this point that the velocity would only change at the valve. If the pressure is constant except at the valve and the velocity decreases soon after the valve, it seems I was over thinking the image in my head.

I think according to the principle of contuity in fluid dynamics, the flow rate should stay the same. Pressure getting slightly lower usually means a transfer of energy so more kinetic energy. Therefore, a slight change in velocity at that point but the increase is dampened by the return to normal pressure levels. Overall, the velocity should remain constant as it flows out of the faucet. By the way, I am assuming this from articles telling me that flow rate can only change through a force or change in mass. I got to thinking about it since I noticed a smaller stream but velocity doesn't increase by a noticeable amount. I assume a smaller area at the valve would mean that a smaller stream comes out. Obviously, this needs to be case since it happens via observation that the stream cross section area is not as wide.
 
  • #10
Can you write down any simple formula showing how the velocity of water through the nozzle varies with the pressure drop across the nozzle ?
 
  • #11
TheWonderer1 said:
It's my understanding at this point that the velocity would only change at the valve. If the pressure is constant except at the valve and the velocity decreases soon after the valve, it seems I was over thinking the image in my head.
Yes. A better example would be a hose with a spray head. There the increased velocity of the water coming out of the restriction is very easy to see. (Or just putting your thumb over part of the end of a hose.)
 

What is the Venturi principle?

The Venturi principle is a fluid dynamics concept that describes the relationship between flow velocity and pressure in a pipe. It states that as the velocity of a fluid increases, the pressure decreases, and vice versa.

How does a faucet use the Venturi principle?

A faucet uses the Venturi principle to regulate the flow of water. The faucet's spout has a narrow opening, which increases the velocity of the water as it passes through. This creates a low-pressure area, allowing air to be drawn in and mixed with the water, creating a steady and aerated stream.

Why is the Venturi principle important in faucet design?

The Venturi principle allows faucets to control the flow of water without the need for additional moving parts. This results in a simple and efficient design, reducing the risk of mechanical failure and minimizing maintenance needs.

What are the benefits of using the Venturi principle in faucets?

Using the Venturi principle in faucet design allows for a more consistent and aerated flow of water. This not only improves the visual appeal of the water stream but also reduces splashing and minimizes water usage.

Are there any limitations to using the Venturi principle in faucet design?

While the Venturi principle is an effective way to regulate water flow, it does have its limitations. It may not work as well in low-pressure systems, and the water flow can be affected by changes in temperature or altitude. Additionally, the narrow opening in the faucet may be prone to clogging if not properly maintained.

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