A Tesla Valve | Hacker News Reader

A Tesla Valve

en.wikipedia.org

197 pointsstazz142 comments

I’m assuming this is being posted due to this recent popular video, which I think is a very well made demonstration of how the valve works:

https://www.youtube.com/watch?v=tcV1EYSUQME

While this is a very cool video, I don't think it demonstrates a Tesla valve that well. In this example, the flame moving isn't really the same thing as a fluid moving with the exception of the gas expansion within the tube that he mentions.

Instead, the flame basically does a BFS (to put it in programmer terms) of the tube instead of actually moving the fluid through the tube. It just also works out that the gas expanding pushes it in the right direction due to the design of the valve.

BFS is big flame search for anyone unfamiliar with the term.

You deserve the upvote for that joke. Well done. (For the uninitiated, it's Breadth First Search).

I agree and I don't see why he couldn't have just used a smoke bomb. I don't see the big difficulty of demonstrating this valve like he mentions at the beginning.

In this particular case, maybe he didn't have a smoke bomb. He clearly isn't a stranger to this sort of thing but he has online commentators commenting that he failed to properly demonstrate the valve. Pretty solid evidence that the valve is hard to demo.

On a positive note the observation about gas expansion probably makes the whole thing more interesting than a plain demo of the valve. His demo is better than a smoke bomb demo.

It would work with fluids also, wouldn't it? It would be cool to watch it submerged in a clear fluid, with a colored fluid forced through in one end.

This is really clever, but I bet there's all sorts of wacky ways that a 3d version of this could be optimized.

It would be really interesting to throw this design into a learning algorithm with an attached fluid simulation to estimate effectiveness. I wonder if anyone's done this. What learning algorithm would be most effective? And I'd love to see what a learning algorithm would come up with. I suspect an optimized version of this would be really organic looking and have lots of weird spirals and things in non-obvious ways.

Akin to this: https://en.wikipedia.org/wiki/Evolved_antenna

And that in turn reminds me of the obscure zig-zaggy convoluted shapes in molecular biology: https://www.youtube.com/watch?v=B_zD3NxSsD8

These are also born out of an evolutionary optimisation process, and probably has a form that is intrinsically linked to its function - we just haven't remotely uncovered yet.

Continuing this line of thought and i am reminded of steganography, hiding complexity in simplicity or objects with several functions. Also encoding by moving things in relation to each other and the mysterious field of emergence. Especially in biology where complexity or patterns can emerge seemingly from nowhere and hide properties that has to do with relations between points instead of the points themselves.

Alogorithms like what you are describing (minus the learning part) are a very active area of research, its quite exciting! https://en.wikipedia.org/wiki/Topology_optimization

It would have to balance multiple objective functions, 1) does it impede fluid flow 2) is it buildable, can it be constructed 3) is it sturdy, will it last, will it perform under the required criteria. Train an AI to turn knobs that drives the parameters (hyper) that generates networks that solve problems across multiple competing objective functions.

Don't generate networks, generate schools that make networks.

Wouldn't surprise me if you would also find a lot of bugs and inaccuracies with the computational fluid dynamics module through that. That is the algorithm would find an optimal solution in simulation and when tested in real life it would turn out not to be nearly as good.

Notable Quotes:

Let the future tell the truth and evaluate each one according to his work and accomplishments. The present is theirs; the future, for which I really worked, is mine.

Money does not represent such a value as men have placed upon it. All my money has been invested into experiments with which I have made new discoveries enabling mankind to have a little easier life.

https://en.wikiquote.org/wiki/Nikola_Tesla

First time I discovered Tesla's Valve through this post back in 2013 [0]. Author did some extensive testing on its functionality and made some interesting comments/observations about old patents. Highly recommended.

[0] https://fluidpowerjournal.com/teslas-conduit/

This 2000 PhD thesis: http://www.microplumbers.com/pubs/BardellRL-PhDDissertation....

gets into the details (including the math). It also thoroughly defines 'diodicity' (not in wiki or some online dictionaries). I'm wondering if Tesla thought of this while thinking about the operation of diode tubes, and perhaps the idea of electricity as a fluid.

Diode: Fleming valve, 1904. https://en.wikipedia.org/wiki/Fleming_valve

Here's a video showing a microfluidic version of the valve made using shrinky dinks: https://www.youtube.com/watch?v=eNBg_1GPuH0&t=9m15s

So I have one of these in my office. I 3d printed it and tested it. It doesn't really work, but it does give you an interesting flow curve.

IANAFDE (I am not a fluid dynamics engineer).

My gut tells me that for this to work as designed, you would need to ensure the fluid moves exactly as intended, primarily smoothly and evenly. I know nothing about your 3D printer, but if the output is like most I have seen (even high-end ones), I wonder if the surface aberrations in most 3D-printed objects would be enough to impact the fluid flow such that it would be turbulent enough to overcome the intended friction of the channels?

If I had the time, I'd make up a 3D model of this that I could cut on my CNC machine out of a block of aluminum or hard plastic to test.

from playing with 3d printed tesla valves , I think that you're right that surface distortions hinder correct flow.

The way that I created a 3d printed tesla valve that worked was by messing with overall scale. Bigger works better, until suddenly it doesn't work at all.

The idea I had previously about why scale may help was the idea that the scale is gradually turning down the amount that the flow error affects the entire system until eventually the mass of the fluid induces more 'error' into the system until the whole thing destabilizes.

In other words : with 3d printed tesla valves it's vital to find the sweet scale spot between surface-level distortion causing chaos when the valve itself is too small and liquid mass causing chaos when the valve is too big.

That margin between chaos and stability may be made wider by using a finer manufacturing technique, like milling or even SLA/SLS versus FDM. I bet that'd give a wider range of usable sizes.

all that said : even professionally made tesla valves must be made with certain scale constraints in mind. I believe those constraints are first-and-foremost a property of the liquid that's going to be transported.

I'm pretty impressed what you figured out by just experimenting.

What you are describing is the transition between laminar flow and turbulent flow. The point where this transition occurs is governed by the "Reynolds Number". As you correctly discovered, the Reynolds number is influenced by scale and fluid properties (viscosity and density).

The final missing piece is the speed of the fluid, which explains your observation: "Bigger works better, until suddenly it doesn't work at all."

Another useful device in that class is the static mixer. A static mixer splits up a fluid flow into several parts and reassembles them in a different arrangement. Multiple stages mix fluids, using less energy than stirring, especially for high-viscosity materials.

Like the nozzles that attach to those 2-part epoxy syringes? With the “stair steps” inside forcing the A and B components to mix?

Would it be possible to create a pump by just having two of these (or even just one!) and a moving membrane? That would have some interesting applications.

Yes, typical piston pumps have two check valves.

https://en.wikipedia.org/wiki/Check_valve#Pumps

I can do you one better. https://en.m.wikipedia.org/wiki/Tesla_turbine

I have often wondered if a jet engine can be made with a fixed cavity of some sort and no moving parts. One problem seemed to be combustion pushing gasses equally to the exit and inlet. This may be the piece I have been looking for to make it possible.

I think that’s a ramjet.

Right. A few ramjet aircraft and missiles have been built, but since you have to have another propulsion system to get up to ramming speed, it's only useful for special-purpose craft.

The SR-71 engine was effectively a ramjet in some modes. It started up as a turbojet, but at full speed, it was running on ramjet type compression and the fans weren't adding any value. Managing the shock waves and turbulence at the intake end was a huge problem.

Plusejet? https://en.wikipedia.org/wiki/Pulsejet

And if you haven't come across Colin Furze yet, you're in for a treat! https://www.youtube.com/watch?v=zsXWspo5hrc

Interestingly enough a video was just uploaded today on a printed Tesla pulsejet engine that incorporates a Tesla valve.

https://www.youtube.com/watch?v=28XbT11lL24

This device will operate very differently depending on flow rate, therefore the quote "the device acts as a slightly leaking valve" is probably a bit misleading. The Reynolds number determines if the fluid operates in a turbulent or laminar way. The slower the fluid, the lower the Reynolds number and the more laminar it becomes and thus the less effective the valve is.

I can't really see many uses beyond microfluidic applications.

Check out the original patent here https://patentimages.storage.googleapis.com/26/65/c7/c647a84...

What are the practical applications of this? (my imagination is having a failure)

Are there any devices in the wild that use it currently?

The shape reminded me of schematic drawings of veins showing how they have valves to constrain flow towards the heart. Arteries don't need that.

I wanted a diagram or GIF. I get the idea, but boy, it would have helped if wiki had some media.

There's a diagram, it's right at the top.

Here's a direct link if for some reason you can't see images on wikipedia: https://upload.wikimedia.org/wikipedia/commons/5/52/Tesla_va...

https://www.youtube.com/watch?reload=9&v=tcV1EYSUQME

Beat me to it, i thought this was a cool demonstration. I wonder if blowing some fine combustible material, like corn starch, would give embers that we could see to help visualize the flows more precisely.

Also i wonder if these could be used as a suppressor.

Gotta be careful blowing combustible powder around, it can become explosive if ignited.

I think this is a cool but really not proper way of showing airflows. Better just add sparkling dust or use Schlieren imaging.

Wiki is editable ;)

I think it's hard to GIF because it's just slow one way, fast the other. It works differently at different pressures, a GIF might not cut it for accuracy.

And Wiki is currently wrong or misleading. The quote from the patient is interesting, but incorrect.

Anyway, another video with gas rather than an explosion -

https://www.grand-illusions.com/tesla-valve-plastic-c2x21140...

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