How fast does water flow from the syphoning method ?

[Erina]

Watching this video of how easy it is to syphon, I was wondering of how to calculate the rate of flow, but I couldn't find out because I needed to know the velocity, but have no idea?

video : 

It seems that the rate of flow has an arc as it slows down once approaching an equilibrium. However, in my own test I didn't syphon into a container, but down the sink, so the flow would have remained constant.

All I know is the Density of the water at 0.99975cm³ at 10°C, and the inner diameter of my pipe being 16mm. Every equation online asks for information I do not have, or that of which I cannot figure out.

How do I calculate how fast the water is flowing (in my experiment with no collection beaker, but down the drain) please ?

[Sensei]

55 minutes ago, Erina said:

Watching this video of how easy it is to syphon, I was wondering of how to calculate the rate of flow, but I couldn't find out because I needed to know the velocity, but have no idea?

Measure the volume or mass of water prior the experiment, start the timer, measure the volume or mass of water after the experiment. Divide. You will have mL/s or g/s (which will be the same, because water has density ~1 g/mL). You can use beaker or graduated cylinder. They have scale printed on them. Record everything using digital camera placed on tripod and analyze video in gfx application.

Edited November 6, 2020 by Sensei

[Erina]

That's a sound approach. I just did the experiment again with 10 litres of tap water, with a 16mm ID pipe (1 metre long) handing about 15cm below the bottom of the container, which emptied itself in 49 second (we'll call it 50sec), which was one 1 litre every 30 seconds.

 

I was sure to hold the submerged orifice to the side to allow the maximum flow of water after I noticed it struggling

[Sensei]

9 hours ago, Erina said:

That's a sound approach. I just did the experiment again with 10 litres of tap water, with a 16mm ID pipe (1 metre long) handing about 15cm below the bottom of the container, which emptied itself in 49 second (we'll call it 50sec), which was one 1 litre every 30 seconds.

In science, each experiment should be repeated multiple times, and calculated average/mean of samples.

Then repeat this with pipes of different diameters and pipe lengths to see how the results vary (or not).

When you will have enough data, you can enter them on the graph (in e.g. OpenOffice Spreadsheet or Excel). Then derive universal math equation taking diameter of pipe as parameter.

Then repeat this with different fluids e.g. alcohol, oil etc. etc. to see how the results vary (or not).

Edited November 7, 2020 by Sensei

[John Cuthber]

This might save you a lot of time repeating  experiments done long ago.
https://en.wikipedia.org/wiki/Hagen–Poiseuille_equation

[Sensei]

@Erina don't listen to party pooper. Have fun figuring it out by yourself.

[Erina]

It was more the understanding of how to figure it out that I wanted to know. However, calculating from an average is ultimately the right approach, as well as experimenting with different fluids..

 

Thanks for your help.