I had a personal brush with Feynman with regards to this experiment.
Circa 1986, I read Surely You're Joking, Mr. Feynman and became mildly obsessed with the fact that Feynman doesn't present the result of the sprinkler experiment (see the first few seconds of the video for context). A number of colleagues (at the software startup where I was working) and I tied ourselves up in knots debating what the answer must be.
I wanted to perform the experiment, but lacking materials, skill, and (frankly) ambition, I settled for a laughably primitive apparatus involving a couple of bendy straws, the bathroom sink, and my mouth. This was enough to reproduce the well-known fact that if you push water out through the sprinkler, it will spin. When I tried sucking water in, it would give a momentary rotational jerk and then stop moving... but perhaps that was due to my mouth tightening up on the straw?!?
After I shared this inconclusive result, one of my co-workers decided to get to the bottom of the matter. He called the Pasadena operator, asked for the home phone of a Mr. Richard Feynman, and – to my utter horror – dialed the number.
It seemed impossible that this was a viable procedure for making contact with a Nobel Prize-winning physicist, but through the speakerphone, we could all hear a gruff voice that certainly sounded like it might be him. All doubt was removed when my friend explained that we were looking for the answer that isn't presented in the book, and the gruff voice said, "Why should I tell you?"
Feynman then asked whether we had tried the experiment, and to my redoubled horror, the phone was handed to me. I stumbled through some explanation of what I had tried and what result I had observed. Fenyman then relented, and explained the entire situation in ten short words:
"The sprinkler cannot rotate, because no angular momentum is transferred."
(Not an exact quote, but something very much like that)
That's basically saying that it's sucking air from all directions, not predominantly from the direction the pipe is facing. Counterintuitive to say the least.
My understanding here is shallow, but I think you are correct.
Here's a simple exercise to help your intuition: open your hand up flat, and hold it facing your mouth, a few inches away. Blow, and you can easily feel the air pressing on your palm. Now inhale sharply; your hand will feel no suction at all.
That's true, but all the air molecules entering a tube aligned with X axis have negative momentum along X. You'd think this means the total X momentum of all molecules become more positive.
If you watch the whole video, it ends with Mathias asking for help understanding why a straight tube would also lift when sucking air in. There's a short companion video that provides the answer:
Perhaps I’m missing something but it all felt sort of underwhelming to me? I won’t claim to have predicted the motion of the thing prior to watching, but watching his demonstration was not very surprising or counter intuitive.
What am I missing exactly? I’ll admit I only made it about halfway through the video…
The jitter is likely due to the suction pulling the air from the outside of the tubes, which then get pulled in the gap between the things - which does so in a buffeting fashion due to the movement of the pipes, so it finds the oscillation... (the tubes are a Foil - so you have to accomodate the flow diff on the external and internal of your receiving tube - and how the flows from the outside of the foil are a diff speed/flow/rate than the center of the tube - thus the light suction guy gets enough strength for the outside air to push it back - once it gets far enough from the horizontal tube, the pressure from the outside flow drops and the lever goes back to its resting position and begins again)
The other thing, as he mentioned eddys -- the inlet and outlet cones should be turbine-spiral shapes - as the air/fluid comes down the pipe, if you give it a spiraling/riffling it will keep the flow somewhat cohesive as it spins it.
Further, as a YT comment mentioned - stuffing a bunch of small straws in the main tube helps, because if you have a lot of smaller tubes - (especially with water) you can get the effective "orientation of the molocules" the same - so your stream can be more cohesive (this method was (invented?employed) by Disney Land Engineers when they were building the fountains that shoot clean, cohesive lasers of water.
They run the streams to the fountain through pipes that have a ton of staws inside - so the water gets orientated in such a way that when the stream leaves the nozzle, the water stays together.
"After graduating from Stanford, Fuller worked as an Imagineer for The Walt Disney Company, applying the laminar flow technology he developed and refined to create Disney's “Leapfrog” fountain feature at Epcot Center."
There are certainly eddy currents within the heart, but the heart is not an eddy pump. As pumps go, the heart is most similar to a reciprocating volumetric pump.
> stuffing a bunch of small straws in the main tube helps, because if you have a lot of smaller tubes - (especially with water) you can get the effective "orientation of the molocules" the same - so your stream can be more cohesive
This is not the right way to think about it. The straws reduce turbulence by preventing fluid motion in a radial direction, and reduce swirl by preventing a swirling motion. (The screens have similar effects.) Both turbulence and swirl prevent the formation of a coherent liquid jet. The straws (and screens) aren't without disadvantages as they will cause significant pressure losses.
How I know: I did a PhD on the range of large fire-fighting water jets and ended up reading a LOT of laminar fountain stuff online out of curiosity.
> this method was (invented?employed) by Disney Land Engineers when they were building the fountains that shoot clean, cohesive lasers of water
Definitely employed. Flow straighteners (or flow conditioners, or whatever you want to call them) were quite common for turbulence and swirl reduction in general before laminar fountains appeared. I recall seeing patents with flow straighteners for fire-fighting purposes in the 1930s, and I'm confident that they were in use in other areas earlier than that.
***
A side note: Laminar fountains are neat, but you'll find a ton of misinformation about how they work online. I started writing more, but Brandolini's law comes into play, and I don't have the time to go into it.
I'm not familiar with FluidX3D. Lattice Boltzmann methods are uncommon, probably because they are computationally expensive. I'm a finite volume and finite difference guy myself. Finite volume methods are the most common approach in computational fluid dynamics.
Do you recall they showed the blip that the google folk made, and it was in the hangar at Moffett field... they were showing all the different motors and sensors - and it was brought up that they had LIDAR sensors pointing at the interior helium balloon... and someone asked why they would be lidaring the thing...
I surmised that they were using it to calculate the internal volume due to the deformation of the balloon as it loses volume.... was I correct?
Circa 1986, I read Surely You're Joking, Mr. Feynman and became mildly obsessed with the fact that Feynman doesn't present the result of the sprinkler experiment (see the first few seconds of the video for context). A number of colleagues (at the software startup where I was working) and I tied ourselves up in knots debating what the answer must be.
I wanted to perform the experiment, but lacking materials, skill, and (frankly) ambition, I settled for a laughably primitive apparatus involving a couple of bendy straws, the bathroom sink, and my mouth. This was enough to reproduce the well-known fact that if you push water out through the sprinkler, it will spin. When I tried sucking water in, it would give a momentary rotational jerk and then stop moving... but perhaps that was due to my mouth tightening up on the straw?!?
After I shared this inconclusive result, one of my co-workers decided to get to the bottom of the matter. He called the Pasadena operator, asked for the home phone of a Mr. Richard Feynman, and – to my utter horror – dialed the number.
It seemed impossible that this was a viable procedure for making contact with a Nobel Prize-winning physicist, but through the speakerphone, we could all hear a gruff voice that certainly sounded like it might be him. All doubt was removed when my friend explained that we were looking for the answer that isn't presented in the book, and the gruff voice said, "Why should I tell you?"
Feynman then asked whether we had tried the experiment, and to my redoubled horror, the phone was handed to me. I stumbled through some explanation of what I had tried and what result I had observed. Fenyman then relented, and explained the entire situation in ten short words:
"The sprinkler cannot rotate, because no angular momentum is transferred."
(Not an exact quote, but something very much like that)