How does water flow from a faucet?

In summary: Thicker and with the "gravity" turned down a bit.A bit thicker and with the "gravity" turned down a bit.
  • #1
richengle
26
1
water flow from a faucet will neck down its radius as it flows to the bottom of the sink. It is asserted that this is due to the fact that gravity increases the velocity of the fluid. This is shown at . I am trying to simulate this, and am not having much luck. shows this for a flat surface. Most normal faucets aren't like that. Has anyone seen a good simulation, with explanation of methods for a standard faucet, preferably with flow in the sink as well?
 
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  • #2
What is described in the first video is a good physics problem to work through, but it does not represent the actual behavior of real water from real faucets. If you look at that, you will see that water rather quickly forms into drops.

So, do you want to describe the "toy" model or something more realistic. A more realistic model probably doesn't have a closed form solution.
 
  • #3
id like to model water from a faucet. my simulations have it just running straight down, and not necking. it must neck because outside pressure is greater than inside pressure, no?
 
  • #4
Don't forget surface tension. If the stream breaks into drops, surface tension probably dominates.
 
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  • #5
richengle said:
id like to model water from a faucet. my simulations have it just running straight down, and not necking. it must neck because outside pressure is greater than inside pressure, no?
What are using to model it?

If I do a quick default setting fluid sim with Blender, I get necking:

tap_flow.png

This is one frame of the simulation.
 
  • #6
Janus said:
What are using to model it?

If I do a quick default setting fluid sim with Blender, I get necking:

View attachment 276037
This is one frame of the simulation.
cool. blender with manta, right? how long of baking to make 5 sec of simulation?
 
  • #7
richengle said:
id like to model water from a faucet. my simulations have it just running straight down, and not necking. it must neck because outside pressure is greater than inside pressure, no?

No. Pressure at both sides is equal (except for surface tension effect). The flow necks because it accelerates due to gravity and needs to confirm to the continuity equation (no water is lost).
 
  • #8
richengle said:
cool. blender with manta, right? how long of baking to make 5 sec of simulation?
On my machine it takes about 3 min total bake time (data and mesh), without particles ( foam, spray or bubbles) for 5 sec. This is with a fluid resolution set at 96.*
This sim is about 3 1/3 sec long, and includes some bubbles and spray. Most of the time is taken in rendering the frames (Over an hour for 80 frames)
water_tap.gif

It is somewhat grainy as I converted it to a compressed GIF in order to get the file down to a size I could directly upload here.

*Your bake times may vary.
 
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  • #9
Here are a couple of more examples produced by playing around with the viscosity of the the fluid.
thckfld1.gif


A bit thicker and with the "gravity" turned down a bit.
thkfld2.gif

That bit where it kind of hangs there and spurts out was not planned, but this kind of thing can happen with Blender, where a tweak in the settings can produce unintended results.
 

Related to How does water flow from a faucet?

1. How does water flow from a faucet?

Water flows from a faucet due to the force of gravity. When the faucet handle is turned on, it opens a valve and allows water to flow through the pipes and out of the faucet.

2. What causes the water to stop flowing from a faucet?

The water flow from a faucet stops when the faucet handle is turned off, closing the valve and stopping the flow of water.

3. Why does the water flow from a faucet at different rates?

The rate at which water flows from a faucet can vary depending on the water pressure in the pipes, the size of the faucet's opening, and any obstructions or blockages in the pipes.

4. Can the temperature of the water affect its flow from a faucet?

Yes, the temperature of the water can affect its flow from a faucet. Cold water is denser than hot water, so it may flow more quickly through the pipes and out of the faucet.

5. How can I control the flow of water from a faucet?

The flow of water from a faucet can be controlled by adjusting the faucet handle. Turning the handle to different positions can increase or decrease the flow of water.

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