Tesla valve(en.wikipedia.org)
en.wikipedia.org
Tesla valve
https://en.wikipedia.org/wiki/Tesla_valve
42 comments
"Turbulence is the most important unsolved problem of classical physics." -- Richard P. Feynman
"I am an old man now, and when I die and go to heaven there are two matters on which I hope for enlightenment. One is quantum electrodynamics, and the other is the turbulent motion of fluids." -- Miller
According to an apocryphal story, Werner Heisenberg was asked what he would ask God, given the opportunity. His reply was: "When I meet God, I am going to ask him two questions: Why relativity? And why turbulence?"
The Tesla Valve design is turbulence harnessed. When it comes to simulations of such, expect ... discrepancies.
"I am an old man now, and when I die and go to heaven there are two matters on which I hope for enlightenment. One is quantum electrodynamics, and the other is the turbulent motion of fluids." -- Miller
According to an apocryphal story, Werner Heisenberg was asked what he would ask God, given the opportunity. His reply was: "When I meet God, I am going to ask him two questions: Why relativity? And why turbulence?"
The Tesla Valve design is turbulence harnessed. When it comes to simulations of such, expect ... discrepancies.
Can't the simulation at least give some error bars?
Just asking that, you are not familiar with the horror of turbulence. I put those quotes in for a reason: some very great minds have stared into the abyss of turbulence. The Navier-Stokes equations have a "smoothness problem" where some values sometimes go to infinity. Error bars on infinity ...
This makes no sense whatsoever, maybe the abyss has stared back? Turbulent flows can be quite predictable, as the fluctuations smooth out statistically. Even simple turbulence models are quite accurate when it comes to the effect of turbulence, say, in pipe flow, or over flat plates and airfoils. Even for situations in which that is not the case, why would error bars go to infinity?
As to the smoothness problem, that may get you to claim a $1,000,000 Millenium prize in mathematics, but plays no role whatsoever in practical simulations.
As to the smoothness problem, that may get you to claim a $1,000,000 Millenium prize in mathematics, but plays no role whatsoever in practical simulations.
That's a great question and indeed a full research direction -- uncertainty quantification. Unfortunately it turns out that it's not that simple.
It's really not, though. It wouldn't work in laminar micro fluid applications otherwise.
"laminar" and "micro" makes me think you've "solved" turbulence by stringently avoiding it at all costs.
I'm not solving anything and I did not bring turbulence into this. Parent wrote that the Tesla valve harnesses turbulence to function, I gave a counterexample of how Tesla valves are applied for laminar microflows, ergo turbulence cannot be the working principle behind Tesla valves.
It's very easy. Mind you that 'simulation' means you're trying to solve a system of partial differential equations at tens of thousands to billions of positions simultaneously.
The simple truth is that computational fluid dynamics codes are nowhere near a calculator-like fire-and-forget reliability, even though the UI of commercial solvers implies as much when you just have to click a button to get 'an answer'. It's still much more of a black art and you really have to know (1) the physics, and (2) the numerics to reliably generate physically meaningful results.
The simple truth is that computational fluid dynamics codes are nowhere near a calculator-like fire-and-forget reliability, even though the UI of commercial solvers implies as much when you just have to click a button to get 'an answer'. It's still much more of a black art and you really have to know (1) the physics, and (2) the numerics to reliably generate physically meaningful results.
For the same reason why we still use wind tunnels and a lot of other types of physical simulations when it comes to fluid dynamics and many other fields of “classical” applied physics.
The reality is that all the equations and formulas we use are approximation, even simple things like the actual direction of flow in a pipe aren’t as simple as you think take any pipe and flow fluid through it in one direction, now introduce a dye in the middle and without a recirculating system the dye will eventually creep up against the flow.
None of the equations you can nominally apply to fluid flows would enable you to predict nor explain this. There are now diffusion calculations that you can apply to calculate how much and how fast things could diffuse upstream, but these are essentially statistical models that we derived from experiments.
So back to the Tesla valve question, the simulation likely work on ideal flows and geometries which are nearly impossible to actually produce through engineering so the slightest of variations in the surface, fluid density etc. can have drastic impacts on the outcome.
The reality is that all the equations and formulas we use are approximation, even simple things like the actual direction of flow in a pipe aren’t as simple as you think take any pipe and flow fluid through it in one direction, now introduce a dye in the middle and without a recirculating system the dye will eventually creep up against the flow.
None of the equations you can nominally apply to fluid flows would enable you to predict nor explain this. There are now diffusion calculations that you can apply to calculate how much and how fast things could diffuse upstream, but these are essentially statistical models that we derived from experiments.
So back to the Tesla valve question, the simulation likely work on ideal flows and geometries which are nearly impossible to actually produce through engineering so the slightest of variations in the surface, fluid density etc. can have drastic impacts on the outcome.
So the simulations are off by a factor of 10? How is this possible?
It's hard to say since there is zero information about how the simulation they mentioned was done in the footnoted article. Most likely they either screwed up the mesh or the, more likely, the turbulence modelling. It's hard to say why the Wikipedia author chose that particular article/simulation results, since the article presenting the results is very superficial. If you look at results from other simulations you can find numbers between 1.5-7 depending on the exact simulation setup.
If you read the paper linked to in the footnote to the steady flow experiment you'll see that the results are very dependent on the turbulence and Reynolds number of the liquid so how you feed the liquid into the valve (how fast and how steady) can greatly impact your results. So if the simulation and the experiment used different pressures for the water entering the system, just that could explain some of the discrepancy.
It's hard to say since there is zero information about how the simulation they mentioned was done in the footnoted article. Most likely they either screwed up the mesh or the, more likely, the turbulence modelling. It's hard to say why the Wikipedia author chose that particular article/simulation results, since the article presenting the results is very superficial. If you look at results from other simulations you can find numbers between 1.5-7 depending on the exact simulation setup.
If you read the paper linked to in the footnote to the steady flow experiment you'll see that the results are very dependent on the turbulence and Reynolds number of the liquid so how you feed the liquid into the valve (how fast and how steady) can greatly impact your results. So if the simulation and the experiment used different pressures for the water entering the system, just that could explain some of the discrepancy.
You seem to know a thing or two. Could you point me to an intro for material/physics simulation? Keywords and such? Some basic ideas or even tutorials how this is approached and the common pitfalls?
Is water simulated like gas, sand, or spaghetti? Are internal grid configuration and electromagnetic properties considered usually? Water's chemistry and physics makes it such a special thing, no? What's the scale when things commonly fall apart? Is quantum computation a possible answer to scalability? Can you "divide and conquer" a fluid system? Do real life model measurements tell you much about upscaled applications?
I only know people hate fluid dynamics studying physics and that it's a hard problem.
Is water simulated like gas, sand, or spaghetti? Are internal grid configuration and electromagnetic properties considered usually? Water's chemistry and physics makes it such a special thing, no? What's the scale when things commonly fall apart? Is quantum computation a possible answer to scalability? Can you "divide and conquer" a fluid system? Do real life model measurements tell you much about upscaled applications?
I only know people hate fluid dynamics studying physics and that it's a hard problem.
When it comes to fluids (and gases) the keyword you are looking for the the Navier-Stokes equation. In most cases gases and fluids can be handled essentially the same way.
There is pretty a good video introduction to Navier-Stokes here:
https://youtu.be/ERBVFcutl3M (part 1)
and
https://youtu.be/wtIhVwPruwY (part 2)
The big 'problem' with fluid dynamics is that from the equations it looks like a really simple problem. The Navier-Stokes equation is a couple of lines and you can explain it to a reasonably smart high school student who has taken calculus.
And in the 'easy' case where you assume laminar flow and no turbulence it is pretty easy. The problem is when you introduce turbulence into the system then it becomes basically unsolvable and you are forced to rely on 'tricks' and approximations to make the problem computable. Most of the 'art' of CFD is picking the right tricks and approximations to solve the particular problem you have (the second 'art' is creating and a good mesh to run the solver on).
The big 'problem' with fluid dynamics is that from the equations it looks like a really simple problem. The Navier-Stokes equation is a couple of lines and you can explain it to a reasonably smart high school student who has taken calculus.
And in the 'easy' case where you assume laminar flow and no turbulence it is pretty easy. The problem is when you introduce turbulence into the system then it becomes basically unsolvable and you are forced to rely on 'tricks' and approximations to make the problem computable. Most of the 'art' of CFD is picking the right tricks and approximations to solve the particular problem you have (the second 'art' is creating and a good mesh to run the solver on).
Just guessing, but I think water is more compressible than how it's commonly modelled.
It's really not for almost all encounters we will ever have with it. In fact, you can model even air (or other gases) as incompressible as long as the Mach number is <0.3 with really good accuracy.
There is an youtube video[1] by the excellent channel Huygens Optics which goes through trying to make a microscopic tesla valve.
The valve does not work as a checkvalve (it is sufficiently small that surface tension and all that work differently than in a macroscopic system), but the author argues that it did satisfy the real goal of being a tesla valve -- which is to look sexy and high tech.
[1]https://www.youtube.com/watch?v=gQnmP7UD_zk
The valve does not work as a checkvalve (it is sufficiently small that surface tension and all that work differently than in a macroscopic system), but the author argues that it did satisfy the real goal of being a tesla valve -- which is to look sexy and high tech.
[1]https://www.youtube.com/watch?v=gQnmP7UD_zk
I tried to carve one of these in styrofoam just to show it to the kids after reading about it a year or so ago, but the material was too soft/porous. It's on my project TODO list if I can ever talk the wife into letting me buy a 3d printer or glowforge.
Forgiveness, not permission. :)
Haha, cash isn't the limiting factor -- it's the hours of disappearing into the workshop to leave her with childcare duties. I just need to wait for the kids to get a bit older and I can make it a team activity.
Yeah. Cherish that time, tho. Kiddos grow up so fast.
For a fun visual demonstration, check out nighthawkinlight's video where he runs a flamefront through one -- https://www.youtube.com/watch?v=tcV1EYSUQME
Also seconding the Huygen's optics video osamagirl69 already posted below -- https://www.youtube.com/watch?v=gQnmP7UD_zk
Also seconding the Huygen's optics video osamagirl69 already posted below -- https://www.youtube.com/watch?v=gQnmP7UD_zk
Tesla was quite the polymath.
Was I the only one who assumed it's gonna be some new Tesla (the company) product?
> Steady flow experiments, including with the original design, however, show smaller ratios of the two resistances in the range of 2 to 4.
I looked at the linked article [0] for this statement and I was hoping to see other passive check valve designs. But it mostly looked like the original Tesla design. Have there been optimizations of the design that achieve a better performance since the original Tesla design?
[0] https://www.nature.com/articles/s41467-021-23009-y
I looked at the linked article [0] for this statement and I was hoping to see other passive check valve designs. But it mostly looked like the original Tesla design. Have there been optimizations of the design that achieve a better performance since the original Tesla design?
[0] https://www.nature.com/articles/s41467-021-23009-y
Does anyone know, if there is research into hygenic aspects of Tesla valves compared to traditional ones? Like biofilm formation experiments?
I was yesterday wondering, if it would make sense to include these into household water piping to ensure mono directional flow, preventing contamination from dirty ends. Doesn't my faucet current create suction on the washing machine's connection? Then again a Tesla valve may be a bio-safespace itself, as there are probably pro-life areas around the turbulences, different water exchange rates and maybe even different gas (oxygen) concentrations.
Also why isn't the cold water line used to dehumidify the shower?
I assume my "smart" ideas about water infrastructure would mostly get me killed by legionella at some point. Excessive regulation on touching the water probably isn't just for killing the fun and creating jobs...
(I recently learned all water pipes are covered in biofilm after 2-3 years, even tho there is hardly any bacteria cell in my country's water. So, there seems to be a disgusting and probably fragile ecosystem to consider...)
I was yesterday wondering, if it would make sense to include these into household water piping to ensure mono directional flow, preventing contamination from dirty ends. Doesn't my faucet current create suction on the washing machine's connection? Then again a Tesla valve may be a bio-safespace itself, as there are probably pro-life areas around the turbulences, different water exchange rates and maybe even different gas (oxygen) concentrations.
Also why isn't the cold water line used to dehumidify the shower?
I assume my "smart" ideas about water infrastructure would mostly get me killed by legionella at some point. Excessive regulation on touching the water probably isn't just for killing the fun and creating jobs...
(I recently learned all water pipes are covered in biofilm after 2-3 years, even tho there is hardly any bacteria cell in my country's water. So, there seems to be a disgusting and probably fragile ecosystem to consider...)
I don't know how "leaky" a tesla valve is and if that leakiness (if it's non-zero) matters to the (pulsejet ? microfluids ?) applications it is used in.
Generally speaking, any volume of household/utility water is considered sewage if even one drop of sewage enters it.
In California, utility connections utilize double-check valves with inspection ports that allow an inspector to regularly check the expected pressure drop between the two check valves and ensure they are not leaking.[1][2]
I don't know if that is more, or less, aggressive than a Tesla valve with (for instance) 8 or 10 "segments".
[1] https://en.wikipedia.org/wiki/Double_check_valve
[2] https://www.mscdirect.com/product/details/65889354
Generally speaking, any volume of household/utility water is considered sewage if even one drop of sewage enters it.
In California, utility connections utilize double-check valves with inspection ports that allow an inspector to regularly check the expected pressure drop between the two check valves and ensure they are not leaking.[1][2]
I don't know if that is more, or less, aggressive than a Tesla valve with (for instance) 8 or 10 "segments".
[1] https://en.wikipedia.org/wiki/Double_check_valve
[2] https://www.mscdirect.com/product/details/65889354
Thanks.
This made me checking the situation in Germany. Apperently the washing machine needs a backflow protection by law. Not sure mine has one as it's just a simple looking double faucet (washing machine + sink connection). Maybe that's going to the long list of "deadly" oversights by my landlord XD
Either way, I read modern washing machines prevent this also by their own valve systems. Guess that's the fancy thingy at the end of the water connection. Hope that stops whatever is making notable hydrogen sulfide in the freshwater inflow from spreading into my drinking water... What do they even eat??
For real washing machines and fridges are just increasingly disgusting if you start asking questions... Really glad for my immune system.
This made me checking the situation in Germany. Apperently the washing machine needs a backflow protection by law. Not sure mine has one as it's just a simple looking double faucet (washing machine + sink connection). Maybe that's going to the long list of "deadly" oversights by my landlord XD
Either way, I read modern washing machines prevent this also by their own valve systems. Guess that's the fancy thingy at the end of the water connection. Hope that stops whatever is making notable hydrogen sulfide in the freshwater inflow from spreading into my drinking water... What do they even eat??
For real washing machines and fridges are just increasingly disgusting if you start asking questions... Really glad for my immune system.
The flowback protection is usually directly attached to the water inlet of the washing machine.
It's not an optional thing that a landlord can skimp on, you'd have to replace the inlet entirely to get rid of it.
It's not an optional thing that a landlord can skimp on, you'd have to replace the inlet entirely to get rid of it.
Thanks.
You mean e.g. this techy thing at the end of the inlet tube right? It's electrical and only opens when the machine needs water, correct? I think I read a warning about electrical hazards for this plastic tube.
On the downside, this valve probably doesn't allow flushing the inlet with some hypochlorite solution easily... Well knowing the drinking water is safe helps. Hydrogen sulfide is detectable in such low quantities, I am probably stressing over very little contamination anyway.
I wonder if you could reconstruct the whole of "western" civilization just from norms and regulations :)
You mean e.g. this techy thing at the end of the inlet tube right? It's electrical and only opens when the machine needs water, correct? I think I read a warning about electrical hazards for this plastic tube.
On the downside, this valve probably doesn't allow flushing the inlet with some hypochlorite solution easily... Well knowing the drinking water is safe helps. Hydrogen sulfide is detectable in such low quantities, I am probably stressing over very little contamination anyway.
I wonder if you could reconstruct the whole of "western" civilization just from norms and regulations :)
> Doesn't my faucet current create suction on the washing machine's connection?
Even if it did, it doesn't create any flow, which would be necessary for the valve to function.
Even if it did, it doesn't create any flow, which would be necessary for the valve to function.
Probably a good point. I think I am making the tesla valve more than it is. I am prone to this. Thanks.
You raise an interesting point. I'd definitely want to test them under water main break scenarios, when a bunch of mud and sand &c make their way through the lines. A clear inspection port (whole side, really) would be super cool.
Modern use for it:
https://www.newscientist.com/article/2277794-century-old-wat...
Outstanding. That's the closest thing to free power I've seen.
An interactive simulation of Tesla valve.
https://tinyurl.com/yzcr74gw
If you were looking for a litmus test to distinguish armchair engineers and cranks from people who build things that work, you could do worse than "How important to the future of engineering is the tesla valve?"
Recent discussion (2021 May / 223 points / 64 comments): https://news.ycombinator.com/item?id=27215894
> Steady flow experiments, including with the original design, however, show smaller ratios of the two resistances in the range of 2 to 4.
So the simulations are off by a factor of 10? How is this possible?