11 ms·
Why does a spray bottle work?
- bitofhope 8y agoIt's a simple mechanism, but the writing and diagrams deserve an A+ for clarity.
- bluedino 8y agoA clearer title would be, 'How does a spray bottle work' I'm guessing the authors first language isn't English, but saying 'why' would be better suited to explaining why a spray bottle works for a certain solution or process. Why does a spray bottle work well for watering a plant? A spray bottle produces many small drops of water which is an effective method of covering the leaves of a plant.
- deleted 8y ago[deleted]
- jstanley 8y agoI thought "Why does a spray bottle work?" was a fun way to phrase it. It implies that OP originally believed, upon casual inspection, that it shouldn't work at all.
- otras 8y agoAuthor here, thanks for the feedback! English is indeed my first language, but I am always looking to improve. I chose "Why" for reasons similar to what jstanley wrote. When I was first considering the mechanism, connecting these components by simple tubes seemed like it wouldn't work. Why then did it work? Why does a spray bottle work [when it seems like it shouldn't]? vs. Why does a spray bottle work [well for watering a plant]? I saw that sctb temporarily changed the title to "How", but it looks like we're back at "Why". I apologize if any readers were expecting a more metaphysical discussion about spray bottles, but I'd be more than happy to explore that in a future post!
- amelius 8y agoWouldn't this design create a vacuum in the reservoir? Edit: (reservoir = bottle)
- ninkendo 8y agoNo, because the one-way valve on the bottle end is pointed the other direction, so that it allows fluid into the reservoir, but not back into the bottle.
- ninkendo 8y ago(Too late to edit: you’re using the terms correctly, I was wrong. I was thinking of what the article calls the “staging area”)
- userbinator 8y agoThere is usually a vent somewhere else.
- xenadu02 8y agoThere is usually a small air vent into the bottle. Small enough that fluid tension stops any spillage even when turned upside down. Because it is small you can cause the bottle to collapse if you do a lot of spraying quickly, an effect you might have noticed before.
- deepdiving12 8y agoGreat write-up, awesome diagrams, some parts could use some improvement in language, but the diagrams more than make up for it.
- anotheryou 8y agoHow does the nozzle diffuse?
- jstanley 8y agoI would guess it's just a fine mesh that the liquid is forced through.
- masklinn 8y agoI wouldn't think so, that's how you go from spray to foam (e.g. some household detergents around here have a small mesh screen you can clip over the spray nozzle to get a detergent foam instead of the liquid droplets of a regular spray bottle).
- steve_adams_86 8y agoI think it's actually that the particles are forced to collide at relatively high speed due to the pressure behind the small opening. A mesh could eventually get clogged with minerals or debris, but this approach leaves less room for failure. Basically you're just ripping the fluid into mist with high pressure.
- deltron3030 8y agoIt's just a hole. If you take a hot needle you can widen the hole of spray caps and increase the throughput (and size of the throw if you also increase the distance to the object). Another trick for spraypaint bottles is to stomp them vertically if you run out of spraypaint, it won't hurt the system that takes your cap, and gives you little bit more paint.
- masklinn 8y agoThank you, I was also expecting that information, not an essay on small-scale ball check valves.
- btrettel 8y agoFluid dynamicist here who works on the breakup of larger water jets. How the jet breaks up depends on the design of the system. (I assume you mean break up, not diffuse. Diffusion is a different physical process which occurs independent of breakup.) A low speeds (laminar flow), Rayleigh's analysis shows that a simple liquid jet breaks up due to surface tension effects. https://en.wikipedia.org/wiki/Plateau%E2%80%93Rayleigh_instability https://en.wikipedia.org/wiki/Plateau%E2%80%93Rayleigh_insta... At higher speeds (e.g., transitional or turbulent flows), the mechanisms change. For your typical spray bottle (without a swirl chamber) I'd say turbulence is the primary cause of breakup. Aerodynamic influence won't factor in at typical air densities and cavitation isn't happening as it probably would break the nozzle. Here's a conference paper I wrote on turbulent breakup theory, which hopefully is readable for anyone with an understanding of probability theory and basic turbulence theory: https://engrxiv.org/35u7g/ https://engrxiv.org/35u7g/ (RMS velocity is just the standard deviation of the velocity. Turbulent kinetic energy is an energy formed from the RMS velocity. Kolmogorov's 5/3 theory is used a bit, but you can just view it as power law distribution. Etc.) I also have some small spray bottles with swirl chambers, which makes the bulk fluid spin, destabilizing the interface, leading to droplet formation. The spray angle for these is large compared against the simple pressure atomizer described previously.
- billsix 8y agoHaving source be in the "staging area" after "git add" makes more sense to me now :-)
- jarfil 8y agoI think this use of "staging area" comes from the military use, which in turn comes from the theater "staging", both predating git and the bottle.
- Sharlin 8y agoYep, it’s more likely the author got the ”staging area” from git, as an analogy familiar to software engineers (or else from the military/theater context), it’s not an official fluid dynamics term used by spray bottle engineers. At least I don’t think so :p
- userbinator 8y agoYes, I was a bit bemused by the use of "staging area" and thought the author was deliberately going for an anachronistic effect, in much the same way that (computer) machine instructions were called "orders" in the very beginning. The more common term is just "cylinder".
- jimnotgym 8y agoI am not sure about the military use coming from the theatrical. My understanding is that staging means 'standing place', and that the theatrical stage is just 'something to stand on'. You sometimes get scaffolding called staging in the UK. The military use has the same root but is not derived from the theatre I beleive. A staging area is somewhere you stand and wait. Very similar in use to the staging-posts that a stage-coach goes through. The meaning in git could mean directly this, somewhere to wait, or it could be derived from the further development of the process stages. The stage having become the journey itself rather than the stopping-point. Something is staged because you have completed a stage and are waiting to start the next stage. That is rather circular really. At this stage I will pass you over to an article https://en.wiktionary.org/wiki/stage https://en.wiktionary.org/wiki/stage
- userbinator 8y agoA very simple design, based on a principle that was discovered over 2000 years ago. http://www.mdpi.com/2073-4441/7/9/5031/pdf http://www.mdpi.com/2073-4441/7/9/5031/pdf (see page 13-14) https://en.wikipedia.org/wiki/Piston_pump https://en.wikipedia.org/wiki/Piston_pump
- maym86 8y agoThat diagram at the top of the Wikipedia article made the concept more clear to me than the whole orginal post. Drawing the valves like that really helps. Edit: grammar
- alanbernstein 8y agoThat's funny, I don't know what that diagram is trying to convey.
- barrkel 8y agoI suspect it might have something to do with your mechanical aptitude - the mechanism is suggested by the shapes of the parts. The diagram is reminiscent of those tests we did in school to help choose a career.
- Stratoscope 8y agoYour confusion is understandable, since the Wikipedia article doesn't even make the slightest attempt to explain the diagram. So let me try. Let's start with the piston pump on the left. The brown piece moves up or down in a tube, and the two black "T" figures are valves that open or close in response to water pressure. The down arrow next to the piston indicates that the piston is currently moving down and pushing on the water. This causes the valve at the bottom to close and the valve on the left to open. So water comes out at the top left. After the piston is pushed down as far as it will go, you start pulling the piston back up. This is not shown in the diagram, but now everything is reversed. The valve at the left closes, and the valve at the bottom opens, both in response to the pressure change. So now, water is pulled up from the well or other source, filling the chamber. When it is full, you start pushing down again, and the cycle begins anew: the valve on the left opens and the valve on the bottom closes, pushing water out of the spout at the top left. Once that makes sense, take a look at the plunger pump on the right side of the diagram. You will see that it works on exactly the same principle: when you move the brown part up or down, it pulls or pushes on the water in the same way as the piston pump. The only difference is in the shape of the moving part.
- SimonSword91 8y agoThis is a nice example to show the illusion of explanatory depth [0]. Most people would say they know how a spray bottle works, but fail to describe all relevant details of the implementation, [0] https://www.edge.org/response-detail/27117 https://www.edge.org/response-detail/27117
- mertd 8y agoThere is a relevant interview [0] with Feynman that I always remember. [0] https://www.lesswrong.com/posts/W9rJv26sxs4g2B9bL/transcript-richard-feynman-on-why-questions https://www.lesswrong.com/posts/W9rJv26sxs4g2B9bL/transcript...
- Fnoord 8y ago> If you asked one hundred people on the street if they understand how a refrigerator works, most would respond, yes, they do. But ask them to then produce a detailed, step-by-step explanation of how exactly a refrigerator works and you would likely hear silence or stammering. This is a terrible example because its essentially a trick question. The illustration would highly depend on context. Say you meet someone on the street and you casually ask them this question, or you ask this on a birthday. "Works" with regards to a refrigerator refers to "knowing how to operate", or perhaps the basics. Whereas if its for the TV quiz program "engineering of the kitchen" or "an applicant for technician repairing Samsung's refrigerators", yes then its clear that more depth is meant. That's not to say the Dunning-Kruger effect doesn't apply here. Its just that there's a level set for a debate due to the context which then presets also the level of the expected answer.
- richardfeynman 8y agoMichael Faraday gave a great series of lectures on how candles work that also illustrates the difference between cursory knowledge and explanatory depth. Most people think they know how candles work, but when you dive into the details there are all sorts of interesting things going on. https://en.wikipedia.org/wiki/The_Chemical_History_of_a_Candle https://en.wikipedia.org/wiki/The_Chemical_History_of_a_Cand... (you can also buy the lectures in book form on Amazon.)
- TheSoftwareGuy 8y agoOne way valves are basically diodes, but for fluids rather than electrons. You can also make logic gates out of just diodes (or one way valves). Imagine writing software for a hydraulic computer!
- mbell 8y ago> One way valves are basically diodes, but for fluids rather than electrons. The analog of the fluid in that analogy is electric charge/current, not electrons which move in the other direction (which kinda breaks the analogy as a result).
- Sharlin 8y agoAnd also move really really slowly compared to the field. Their (net) movement is actually pretty irrelevant to the propagation of what we call electricity an sich.
- rossdavidh 8y agoHowever, I think it would have been quite difficult for me to get the concept of "holes" in semiconductor current, which are positively charged pseudo-particles created by the absence of electrons, if I hadn't been able to think of them as being like bubbles in a fluid. They go the opposite way of the fluid flow, and they are somewhat particle-like. So it's not a totally broken analogy, it does help to clarify some things.
- mbell 8y agoI generally found the fluid analogy did more damage than good for a lot of people in EE school. A lot of people think of electricity as electrons zipping around a circuit at the speed of light due (at least in part) to the water analogy. Having to transition from that world to thinking in charge transfer and fields while electrons move around linearly at a snails pace if at all was very difficult for many people. I'd bet in a poll of the general public, most people think electrons fly around a circuit like water in a pipe, which is of course completely wrong. I guess it's debatable whether the inaccuracy matters or not. But in general, I prefer analogies that are simplifications and leave out details, rather than those that are completely ass backwards from reality.
- davidkuhta 8y agoI found his write-up on MBTA bus mirror positioning to be a short but interesting read as well: https://alexanderellis.github.io/blog/posts/mbta-bus/ https://alexanderellis.github.io/blog/posts/mbta-bus/
- userbinator 8y agoMany of the buses I've seen in parts of southeast Asia have their side mirrors hanging in the front instead of jutting out the side, probably for a similar reason (and the streets there are much narrower too.)
- donarb 8y agoAnother reason that the right side mirror is higher is to prevent hitting passengers as the bus pulls up to a stop. Passengers tend to step up to the curb where the front door opens up as the bus approaches.
- fireattack 8y agoFrom the map I can't tell how the bus can "go through Bennett Alley and continue straight into the bus tunnel". The streets are not aligned, are they?
- otras 8y agoGood call! You're right that "continue straight" might not be the best wording, as they aren't aligned on the map. In real life, they're also not perfectly aligned, but the entrance area to the tunnel is much wider than appears on the map, meaning they can take a slight right to continue down the tunnel. My bet is I was thinking about roads in terms of Boston roads, where going straight is often more of an abstract concept than a true direction. Here's a streetview with Bennett Alley on the right and the bus tunnel on the left if you want to get a feel for the turn: https://www.google.com/maps/@42.3731803,-71.1223078,3a,75y,139.59h,84.47t/data=!3m6!1e1!3m4!1sBV8J62aMITLNkWYsq-qNRA!2e0!7i13312!8i6656 https://www.google.com/maps/@42.3731803,-71.1223078,3a,75y,1... Unfortunately you can't see through to the tunnel from the other side of Bennett [0], but the good news is you can see the 3 buses in action! https://www.google.com/maps/@42.3725618,-71.1225705,3a,85.4y,27.74h,85.66t/data=!3m6!1e1!3m4!1sUtPWI3cNFUs0atO9W-JheQ!2e0!7i13312!8i6656 https://www.google.com/maps/@42.3725618,-71.1225705,3a,85.4y...
- vanilla-almond 8y agoA few years ago, a British inventor appeared on a TV show called Dragon's Den (UK version of Shark Tank) and pitched his idea of an improved spray bottle called the Anyway Spray. Instead of a normal plastic tube inside a bottle with an opening at the end, he designed a tube with millions of tiny perforations along its length. This meant the spray bottle could operate at any angle (even upside down) and could empty all liquid in a bottle with no leftover. Here is a 1 min demo of the spray: https://vimeo.com/195318537 https://vimeo.com/195318537 Here's an explanation of how it works https://www.youtube.com/watch?v=xXk46rvzdpY https://www.youtube.com/watch?v=xXk46rvzdpY And here's the original pitch he made on Dragon's Den https://www.youtube.com/watch?v=RjOvyjeZyIw https://www.youtube.com/watch?v=RjOvyjeZyIw
- fouc 8y agoSeems like he managed to license it to Tesco's range of label products. Good for him.
- nothrabannosir 8y agoGood for us! :)
- MichaelApproved 8y agoWhy isn't this in everything? I'd easily pay an extra few cents to have this in spray bottles. It's such a frustrating problem.
- gxs 8y agoJumping to the conclusion that everything a company does is calculated and delibarate is a mistake I see a lot of people make, but in this case it’s accurate. In a business that operates at a scale of 100s of thousands if not millions of bottles sold annually, cents matter and can make up a significant portion of revenue. With this in mind, there is a huge incentive to get people to buy sooner rather than later and more often. Forcing a small amount to remain in a used up bottle is definitely a benefit to the company even if the product is going to waste. This doesn’t include the cost of implementing something new. I’d imagine a company would do extensive survey based research to understand if the additional customer satisfaction would outweigh the costs/downsides. If it’s not a conscious decision, it’s a nice coincidental benefit to them.
- sbilstein 8y agoI would have loved this explained in my high school physics class
- augbog 8y agoClever blog! Design taking apart :) Hope he does more of these!
- seomis 8y agobecause kitty don't like water, duh
- deleted 8y ago[deleted]
- saagarjha 8y agoIf anyone's curious for more, look up how an atomizer works. It's simpler but requires more background knowledge (namely, the Bernoulli principle).
- trumped 8y agoThe spring might be the reason why a spray bottle doesn't last very long if you re-fill it with a bleach solution, when it was not designed for it?
- intrasight 8y agoWhat I find most frustrating about the current class of spray bottles is that they've removed the ability to unscrew the head, and therefore you can't a) get out the liquid which can't be sprayed, or b) reuse the bottle.
- mirimir 8y agoThis is cute and all, but still silly. At least, for those of us whose childhoods included dependence on wells with hand pumps. Or particularly, responsibility for maintaining said hand pumps. Because it's an ancient design. Old ones used leather flaps as one-way valves. Same for tire pumps.
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- plaidfuji 8y agoI know why I clicked on this; one of my cleaning spray bottles just broke. What's everyone else's excuse?
- test6554 8y agoI was literally just thinking "how does this work" when looking at a spray bottle yesterday. Thanks!