Building a Better Turbo Funnel (revised)

This project is a remake of Turbo Funnel thing:4925561.

The original project says "We all know very well that water acquires special properties when it swirls and is able to flow at a higher speed through narrow obstacles." - but do we? Does this swirl design make a better funnel?

If water is rotating in our funnel then would not the centrifugal force lower the pressure in the centre reducing the flow?
Whilst water flows somewhat faster through a constriction owing to pressure effects, the actual volume of water is reduced by the area of the constriction. If we make a funnel with a smaller spout it would run slower.

I ask would the swirl pattern on the bowl of the Turbo Funnel have sufficient influence on the flow of water during its brief time in the funnel? I had my doubts but it is an intriguing idea so I decided to put it to the test.

Testing the Turbo Funnel

I decided to shrink the Turbo Funnel enough to fit it onto a 1.5 litre water bottle so that I could measure the time it took to empty through the funnel.

• I needed an identical funnel but plain, without the swirl pattern to compare it with.
• I wondered if the direction of the swirl made a difference because of the debated Coriolis effect? If it did then the Turbo Funnel with swirls in one direction of rotation should be faster than the plain funnel, which itself should be faster than a Turbo Funnel with swirls in the opposite direction. I made funnels with swirls in both directions.
• Finally I wondered if ensuring a straight flow of water would actually be faster than swirling. I created a funnel with straight ribs to test this idea.
  So what was the result?

I could not find any measurable difference between the different designs. The plain funnel was not slower than the other designs.

I have included my design files in turbo_funnel_variations_small.zip and the same designs but full size in turbo_funnel_variations.zip in case you would like to repeat my experiment.

Another variation and tests

Miskkin2 (the creator of Turbo Funnel) draws my attention to his second design (see the Comments on this Thing) explaining the swirl design - see (Another Turbo Funnel thing 4944971)[https://www.thingiverse.com/thing:4944971].
In the description of that Thing he points to scientific papers which demonstrate that a rotating flow through a pipe runs faster because the turbulence breaks down the connection between the liquid flowing in the centre of the pipe and that flowing at the walls of the pipe which is slowed down by friction.
There is a paper in English which explains the effect here: https://arro.anglia.ac.uk/id/eprint/704518/1/Onimowo_2018.pdf

This lead me to wonder if putting a swirl inside the spout of the Turbo Funnel would have more effect than the swirl in the bowl.
The spout has a more pipe-like shape than the bowl. Being a smaller diameter, the friction effects should be more noticeable in the spout. I also wondered if putting the rotational twist in the opposite direction to the twist in the bowl would improve the turbulence by making the flow of water more at right angles to it, or whether putting the twist in the same direction as the twist in the bowl would enhance the rotation.
I made Turbo Funnels with spout twists in each direction (as per my third photo) with a shape profile as described in the scientific paper which I quote above. I include them in turbo_funnel_twisted_spout.zip in case anyone wants to repeat my experiment.

I tested them by putting them under full flow from my kitchen tap to see which would drain the most effectively. I was unable to notice in my (rather crude) experiment, any practical difference in the performance of the different designs. I am sure that there is a difference one way or the other but believe it to be too small for me to measure. Perhaps someone with better test equipment could achieve a definitive result.
My conclusion is that the length of the bowl and of the spout is probably too short for the profile to have any significant effect on the flow of water. Furthermore the PLA which I used to print these funnels is partially water repellent so that frictional effects are small.

A Better Turbo Funnel

Bernoulli's Theorem states that the flow rate is proportional to the square of the hight of the body of water. Thus if we make a funnel four times the height then we can double the flow. A very tall funnel will not be practical but we can have a quick win by increasing the height of the funnel.

The biggest gain in flow can be achieved by increasing the diameter of the spout. By increasing the diameter by 40% I have doubled the flow rate of the Turbo Funnel, The large spout is 25mm (one inch) in diameter is fine for fuel cans, lawn mowers etc.. I have included a "regular" version with the original size of spout for filling bottles and other smaller vessels.