r/oddlysatisfying • u/Zu_Qarnine • 4h ago
CFD simulations of airflow through vents
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u/Famous_Secret_5174 4h ago edited 3h ago
So what you're saying is, if I'm in the club I should go up to the DJ and request "CFD simulations of airflow through vents"?
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u/Zu_Qarnine 4h ago
make sure you ask for Eddy
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u/jccaclimber 3h ago
Not his early stuff though, just his current work.
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u/GravitationalEddie 3h ago
?
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u/exipheas 3h ago
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u/Mr_Abe_Froman 4h ago
That will maximize flow and get everyone moving.
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u/CyberNinja23 3h ago
John McClane does not approve of the corner turning vanes
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u/technobrendo 1h ago
John was lucky enough to get himself inside a very unique set of ventilation ducts. It had bonus features like the ability to support 200lbs and zero sharp edges or self-tapping screws. Zero dust too.
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u/imgoingtowar 4h ago
Yeah would love to know the track if anyone’s knows
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u/Famous_Secret_5174 4h ago
I shazammed it and it says 'Whatcha Want (Alvaro & Da Funk Remix)'
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u/gorginhanson 3h ago
I didn't realize people cared about vents so much unless they were sneaking through them to a secret spy base
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u/Dawn_Piano 3h ago
Yea most DJs will have COMSOL or some other comparable FEA software that can do this
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u/mattincalif 2h ago
Thank you, I had my sound off until I read this comment. I’m seriously grooving now.
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u/aaclavijo 4h ago
"turning vanes? Crawl through the air ducts they said, it would be easy they said, turning vanes!"
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u/resplendent99 3h ago
"Become a HVAC engineer, you'll have a few laughs!"
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u/Champsmilehighclub 3h ago
As a HVAC engineer whilst this is one of my favourite films, I do regularly use it to point out how amazingly unbalanced the system is. John mclaine hates dampers
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u/ryanxwing 1h ago
As a former HVAC tech you being an engineer makes me wary of you
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u/Mintastic 45m ago
As an HVAC engineer, how often do you build duct systems that can hold a 200lb person?
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u/Champsmilehighclub 42m ago
Tbf I mainly do high integrity systems so almost always, but im aware im the exception not the rule
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u/Droidigan 4h ago
but what about horror game protagonists? where will they go?
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u/Zu_Qarnine 4h ago
video game vents are too spacious
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u/E-2theRescue 2h ago
What do you mean? It's totally normal for a vent to be tall enough to crouch in, with giant box spaces to roam around in, before dropping through a grate that opens up without issue, with nothing blocking it.
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u/dr_mannhatten 1h ago
The Batman Arkham games have the funniest air vents to me. Half of them just lead directly into a cave that’s behind a building, the other half just lead directly to another room. (Also big enough for Batman to crouch inside them, not even have to lay down).
Incredible games though!
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u/foresight310 3h ago
Now do corrugated flex ducts…
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u/hartmanbrah 3h ago
Yeah, I'm watching this while imagining what it would look like for my home AC, which blows through corrigated garbage with 20 degree bends in it.
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u/freeradioforall 2h ago
but total volume that comes out has to be the same right? air cant vanish, so aside from more turbulance, why would it matter?
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u/round-earth-theory 1h ago
You would be correct if your fan was guaranteed to always push a specific volume of air. But that's not how it actually works. Your fan is able to push air up to a certain pressure. That pressure is immediately after the fan, from there the air wants to equalize to lower pressure areas which is ideally the rest of the house. But what we're seeing here is that restrictions cause those high pressure bubbles inside the ducting which means the air doesn't navigate to low pressures as quickly. The ultimate result is reduced air flow out of the vents.
Think of it like a garden hose. If you put your hand on the hose, then you'll be getting less total water out. It'll spray farther because it's still high pressure as it exits the hose, but you get a much lower total volume of water. Your finger is that flow restriction, and the hose isn't able to produce any more flow than the pressure provided by the city.
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u/thelittleking 2h ago
because those inefficiencies that make the air pump work harder translate into a higher power bill
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u/Beard_o_Bees 1h ago
Looking at this model, I wonder if anyone's made a retrofit kit of some kind that you could place at a traditional 'T' junction to make it more efficient?
Seems like you'd just need a piece of plastic/steel/etc in a roughly 'Y' shape and access to the junction.
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u/asianfarmer 4h ago
Off topic, but what genre is this? D&B? House?
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u/Zu_Qarnine 4h ago
I'm not sure what you mean by genre. HVEC in general?
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u/yaboilol24 3h ago
Deep house, deep groove.
Search combinations like that.
Also dub techno can kind of be like this sometimes, although it's usually more mellow
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u/ImSolidGold 2h ago
The 2nd worst kind of electronic music to have a party. Nice for a sunday afternoon afterhour, tho. ;)
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u/ScrivenersUnion 3h ago
I like that they are upfront about the costs associated with the increased efficiency.
In particular I can imagine those turning vanes getting dirty over time, as soon as they're covered in dust and crud I think the friction losses would quickly overtake any increase in flow efficiency. And you'd need someone to go clean them regularly, which increases maintenance.
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u/SoylentGrunt 3h ago
Turbulance, not friction. Even dirty vanes are still superior to a hard turn. Sometimes turbulance is good. It promotes mixing.
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u/rothefro 2h ago
Have to make sure you’re changing out your unit filters to avoid bypassing debris….typically ducts shouldn’t get too dirty as long as you do regular maintenance
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u/finkerlime 2h ago
AC systems already need to be cleaned often
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u/Omnom_Omnath 2h ago
often? lmao, no
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u/ortusdux 2h ago
Depends on the location and quality of the filtration system. Ideally all air is filtered at intake, so minimal dust enters the ducting.
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u/Omnom_Omnath 1h ago
Sure, but i've never heard a homeowner claim AC systems need to be cleaned often. I think I know one person whos had their ducts cleaned out of everyone I know
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u/ortusdux 1h ago
It's a common door-to-door service in my area. It is an easy thing to scare homeowners into.
https://www.epa.gov/indoor-air-quality-iaq/should-you-have-air-ducts-your-home-cleaned
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u/CrashmanX 1h ago
I know 1 person who's moved their fridge to clean out from under it and clean the back of the fridge.
Doesn't mean it shouldn't be done.
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u/tuesmacherie 4h ago
This is actually satisfying as a Master Plumber.
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u/TA_Lax8 2h ago
Also as a woodworker. For dust collection, I've always been told to avoid 90 bends and do two 45s. It's really cool to see that visualized
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u/fritz236 2h ago
Yeah, I've finally gotten everything I need for dust collection except the bends/Y's and this was enlightening.
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u/--------what-------- 3h ago
As a tin knocker, this is fascinating.
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u/Reactin 3h ago
Tinners 20 years ago: *installs VAV after a 90/transition
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u/ArrivesLate 3h ago
This is a good visual of why 3x to 5x duct diameters of straight duct are a standard general note, but also never shown that way. It’s also a good visual of why not to put take offs on those sides of the duct that are blue, but also always shown that way.
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u/happycj 2h ago
I was super fortunate to work for NASA at Ames Research Center back in the 1990s, just when computational fluid dynamics software was emerging on our various supercomputers on site.
As a network engineer and desktop tech support, I got to work hand in hand with the scientists using these tools to visualize airflow over airframes, liquid and gas flows through pipes, and dozens of other applications.
As a homeowner nowadays, I see what the plumbers and HVAC guys are doing for bends and turns and think back to these visualizations I saw back then… it’s cool to be able to see in your head what these invisible flows are like!!
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u/Pansie23 3h ago
Couldn't you put vanes in the one 90 curve to reduce turbulence as well?
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u/Yogi422 3h ago
What software is this? I would play with this all day like it was a game lol
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u/hooligan99 2h ago
not sure what software they used here, but CFD programs in general are usually really expensive - thousands of dollars plus yearly maintenance fees to stay updated with latest versions.
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u/ateaktree 1h ago
There's an attribution in the video... "Simulated with AeroJAX", which does appear to be an open source CFD program.
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u/SwedenGoldenBridge 59m ago
openFOAM is free. Not that it is worst than other paid software at all, very commonly use in academic and industries. openFOAM has no graphical interface but there are other free graphical software that integrate it.
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u/hougaard 3h ago
And this is the reason why a piece of plastic can add horsepower to a Porsche engine :)
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u/TerraCetacea 2h ago
Dang I was literally just in a meeting with some engineers about adding those vanes to doctwork. Awesome to see it visualized
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u/Shoddy_Hand_4577 2h ago
Does anyone know what program this was done in? I haven't touched CFD yet, but it is on my "should get my head around" list, so I would love any advice / recommendations for accessible resources for CFD :)
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u/hooligan99 2h ago
not sure what they used here, but if you already have solidworks, solidworks flow sim is a pretty intuitive and robust CFD program. Expensive, but if you're doing it for work, could be worth it.
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u/Omnom_Omnath 2h ago
The only acceptable price is the lowest it seems when it comes to homebuilders
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u/lenzflare 2h ago
Soooo, the 1x90 vs 2x45 one isn't really about number of turns is it... looks like the effective radius of curvature is the real defining difference. The 2x45 corners essentially make a wider radius of curvature in this case, which results in a gentler turn and so less turbulence. You could stick to 1x90 but with a larger radius of curvature and get a similar improvement.
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u/Office_glen 2h ago
I'm so happy to come here and see things that I work with directly being posted here. I work in sheet metal fabrication, specifically duct work
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u/rm-rf-asterisk 1h ago
Does this simulation account for the million screws poking through?
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u/viotix90 1h ago
As an engineer, this is porn to me. Yeah, baby, make it laminar for me!
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u/Lilwolf2000 4m ago
I'm putting together an older endless pool right now (where the seats around the outside is how the water moves back to the front)... they do the same thing.
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u/23370aviator 3h ago
Most residential applications use flex duct these days anyway. Flex duct is much better insulated than box duct could ever hope to be as well so any losses in the systems efficiency through a not perfectly smooth interior surface are more than made up for by the insulated walls.
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u/LittlePlasticFists 2h ago
Yeah that's not even remotely true. Metal duct has much less friction per foot which increases the efficiency of the blower.
It can also be insulated or lined to provide the same or even higher R-Value as flex duct.
Metal duck work is much more robust and won't fail after being exposed to water once. It's also rodent proof. Somewhat antimicrobial, much easier to clean. I could go on and on.
Flex duct is a great solution when you have a specific problem, and it's much less labor intensive, but it's inferior to metal duct in just about every way.
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u/FluidVeranduh 2h ago edited 1h ago
Flex ducts work well if installed really well. Problem is that they are rarely installed really well.
Flex ducts are chosen in resi because they're less labor intensive and quicker to install, which is attractive to builders trying to make money on volume of houses built.
Losses due to airflow restriction impact more than energy efficiency, it's also noisier and harder on the blower motors.
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u/skilas 4h ago
In construction, I've never need two 45s implemented.
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u/Dawn_Piano 3h ago
Engineers draw them all the time, but one elbow cost less than two so…
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u/iMissTheOldInternet 3h ago
Notably, that looks like the one that has more cons than pros, so it’s probably a niche application, unlike the cheeked up t-junction, which is just better from every angle.
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u/oneeyedziggy 3h ago
I would like numbers please... what speeds and pressures does this really start to be relevant for? Commercial scale? Home scale?
What's the observable result? Lower energy consumption to maintain the same temp? Or does slow turbulent air eventually do the job within an insignificant margin?
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u/gaobij 3h ago
Lower pressure drop = lower blower motor energy consumption. Probably lower noise levels, too. This is true at any scale, but becomes more critical at the airflow capacity limitations of the duct (when the color is this visual is very red).
Numbers are irrelevant here - this is a representation of a best practice and numbers are going to be very specific to the application.
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u/car_buy_2021 3h ago
This is exactly the right question. The simulation output animations do not include the numeric scale that corresponds to the color gradiation.
Ultimately a slight imbalance in velocities or pressures at turns or branches, or turbulence, only matters if there is a negative performance consequence, or possibly a negative reliability consequence, or other negative consequence associated with it.
If the only consequence of this is that one outlet duct receives 0.1% more or less air flow than the one next to it, who cares.
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u/0nlyRevolutions 1h ago
And there's a whole science to generating and validating mesh sizes and defining boundary conditions before you can even start to get results that mean anything!
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u/oneeyedziggy 3h ago
It seems like you could get a lot of this value by just retrofitting the square ducts with a diverter wedge in the square duct, and maybe some rounded corners where the input duct dumps in to minimize negative pressure zones
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u/psychohistorian8 2h ago
any know of good free CFD software we can use to play around with?
wanna build my own F1 car
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u/BondGoldBond007 2h ago
This is why vehicle performance exhaust systems use mandrel bends during fabrication.
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u/Pretty-Resort-7640 2h ago
Oh this is cool. Does anyone have anything similar for water flow? I've always questioned my pool setup and if 90 elbows were The best choice
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u/ripkin05 2h ago
oh yeah this 25 second video on how air vents work totally needs a club dance beat over it for no reason.
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u/LogoMyEggo 2h ago
Makes sense for liquid but how much does it matter for air in an AC duct? Air is compressible unlike liquid, so it can expand and increase flow rate after the bend?
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u/Zu_Qarnine 2h ago
I think compression like in jet engines would need supersonic speed. here it's just an AC pushing the air
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u/GSxHidden 2h ago
I would agree, but wouldnt the last simulation just be a larger surface area for dust and particles to stick to?
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u/FragrantCombination7 2h ago
Does anyone know if the Aston Martin F1 team have an official reddit account? This might be useful info for their research.
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u/graphitehead 2h ago
Now show me cost difference for the additional duct bends and connections.
Efficiency is ultimately the most satisfying though
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u/RecipeFunny2154 2h ago
I thought the vanes part was interesting. Could you put those in a T branch and start getting results closer to a Y branch?
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u/hillmo25 2h ago
Imagine a Y branch made of 4 45* elbows with turning vanes. The air would flow so smoothly.
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u/Gino__Pilotino 2h ago
Corners in ducts are always rounded, guiding vanes do help a lot though with high speed flows.
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u/Synner1985 4h ago
But if you use some of these designs how is John Mclaine going to sneak through the vents to save the day?