[LTT X NASA] How Close is Too Close? Applying Fundamental Fluid Dynamics Research Methods to PC Cooling

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rain3h@reddit

I had a bunch of older 140mm fans laying about so I removed the middles and have been using them as spacers, the sound profile is far more pleasing.

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corruptboomerang@reddit

My napkin maths had me at 2x the normal fan profile being the sweet spot. But 1x is a massive improvement.

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VenditatioDelendaEst@reddit

2x meaning 2x fan height dead space in front of the fan?

I wonder at what point it becomes better to use that space to put an outlet stator+diffuser behind the fan.

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corruptboomerang@reddit

2x the thickness, so fans are 25mm or about an inch, so about 2 inches (50mm).

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VenditatioDelendaEst@reddit

That jives with what I was able to turn up. 50mm is ~0.4d for a 120mm fan. Although that paper was about flat plate obstructions, not distance-along-duct.

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Jeep-Eep@reddit

It looks like many designs have the spacer problem the eLoop had, they just have a particularly pronounced version.

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TwoCylToilet@reddit

What do you mean middles? Could you explain further? I'm always interested in quiet, actively cooled builds.

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Numerlor@reddit

I assume removing the rotor and using just the frame to give an another fan some breathing room

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VenditatioDelendaEst@reddit

I think the acoustic effect might be less dramatic under real-world conditions where the intake plate is the only impedance. Going from near-zero Δp to "some" will necessarily increase turbulence and therefore noise. When there's a whole computer on the outlet side, you start from a higher baseline.
Author of this article is from University of Tokyo. When I was reasearching fan obstructions a couple months back, I ran across a couple of good papers from Japan about it:

https://sci-hub.st/10.1115/fedsm2017-69182
https://sci-hub.st/10.1115/fedsm2014-21251

Interesting effect is that downstream obstructions can sometimes make fans perform better against higher system impedance, by moving the fan into a mixed-flow regime. The centrifugal force from residual swirl in the exhaust works with the flow to contribute a bit of extra pressure rise.

The effect is reversed for upstream obstructions, where the centrifugal Δp works against the flow. Sufficently close inlet obstructions can overcome impeller lift and cause the fan to work (very poorly) backwards.

So if you need to fit a fan in a confined space, better to offset it back a bit rather than having it right in the middle.

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hardware-ModTeam@reddit

This subreddit is not a Youtube Drama subreddit. It's not against the rules to like / dislike a content creator but it is not relevant to /r/hardware.

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CallMePyro@reddit

Exactly everyone! We need to band together and support fellow hardware enthusiasts! It doesn't matter who you are or what you've done in the past - if you're a fan of hardware you have a welcome place in our subreddit!

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Sopel97@reddit

I don't see the point of testing such extreme cases when every sane person has like 10cm clearance at least

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Olde94@reddit

I can see i need to check out some more of their articles! This is great!

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MWink64@reddit

For three decades, it has driven me insane how many case manufacturers can't get it through their thick skulls not to restrict intake fans to the point where they become unnecessarily loud. It's such an obvious flaw in countless cases. I didn't think it required involving NASA to figure out something so obvious. Does this mean I'm a rocket scientist?

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pdp10@reddit

Does this mean I'm a rocket scientist?

Yes, but only at a 1930s level of understanding.

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avboden@reddit (OP)

Video on the subject for those that are interested but the article posted is probably more up this sub's alley.

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Spitfire1900@reddit

They definitely didn’t emphasize in the video well that this was available as an article written by a PHD.

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ThankGodImBipolar@reddit

I honestly do my best to try and forget they even have a website, because it makes me irritated to use it. Whether the data that they collect actually makes it to the website or not is a complete crapshoot, and searching for products which you'd think would have obviously made it there (like the 5070 or 9070XT) only to find nothing is a terrible user experience. That's before you consider the hundreds of displays and headphones that we see Labs data for on Short Circuit. It's a completely useless resource right now, and I'm not surprised that they didn't spend much time plugging it, because it's rarely worth it.

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Plank_With_A_Nail_In@reddit

Your downvoters clearly didn't look at the website, the data they recorded isn't included outside of some jpeg's of charts.

It may well have been written by a PHD but its clearly not a scientific document.

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ThankGodImBipolar@reddit

It's frustrating for me because I love using TechSpot to find HUBs benchmarks, and wish I could use LTT Labs as well, but they've failed to hit the (IMO) minimum viable product of dumping all their data on the website. Not really sure what they've been doing for the past 5 years.

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please_respect_hats@reddit

“The intent of this article is to accompany the LinusTechTips video (and Floatplane exclusive videos) on the testing conducted.”

If I was interested, I would have watched the videos. You can’t see why people take issue with LTT content, and the. attack people for not loving your random Reddit link submission? Lmao

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Exist50@reddit

You can’t see why people take issue with LTT content

So what exactly is the problem with this content? Some people seem to just hate them because GN said they should.

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taz-nz@reddit

They could have just done the math.

The blades area of a 120mm fan is 112mm in diameter giving an area of 9852.03mm2.

Less the 50mm in diameter hub, which has an area of 1963.5 mm2.

Giving you an active area of the fan of 7888.53mm2.

If you put a solid plate in front of fan, the intake area is 480mm perimeter of the fan body x the gap between fan and plate.

So, 7888.53mm2 / 480mm = 16.3mm minimum gap. (The air turning would have some effect too.)

It's not rocket science. If your intake area is less than the active area of fan blades you will have a restriction.

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ritz_are_the_shitz@reddit

they mention in the video that they didn't really need to do all this to find the minimum distance, they did all this to understand what happens to the air when you do go under that minimum. the most interesting part is a vortex where there is airflow acting in the reverse direction

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taz-nz@reddit

Yeah, while I understood with enough restriction the air flow would stall and there would be flow inversion because of the pressure gradient across the blades, the model I had in my mind had the flow looping inward from the tips of the fans towards the hub, but the visualization showing the flow stall at the tips, and loops from the middle of the blades which I didn't expect.

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mundanehaiku@reddit

I'm so glad your account is sticking up for this poor multi millionaire.

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skinlo@reddit

What relevance is his wealth? If he makes a good product or a good video, its fine to say its good.

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260X@reddit

The same LTT that bought a private jet a few days ago, even though the Linus fellow was seen on a 2 year old old WAN clip criticizing Elon Musk for using one, and then the mods on r/LinusTechTips went on a rampage, mass-deleting criticism of the purchase?

r/LinusTechTips reacts very normally to Linus buying a private jet, old anti-private-jet WAN clips resurface, and the mods start deleting again - SubReddit Drama

Nah, why would anyone downvote anything LTT?

Crazy talk!

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FabianN@reddit

No one has actually been about to show a clip to me of him criticizing Elon on his jet.

They've been able to show a clip where Luke reads off the topic on how Elon said he a free speech absolutist, banned the plane tracking account, and that people didn't like Elon's actions. Linus says almost nothing during the topic, the most opinion Linus gives is a comment about how he understands being concerned when the vehicle with your child in is stopped and blocked.

Is there another clip I'm missing?

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StickiStickman@reddit

I was able to find a comment with clips from multiple WAN shows where he's talking about how dumb private jets are in under a minute of searching. Here's one with timestamp.

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FabianN@reddit

No Elon in that clip.

He did say he's interested in trying it, and made it clear he personally doesn't think it is something he can support. Describing that as him saying private jets are dumb is a mischaracterization of that moment.

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Wakakokokaka@reddit

Damn, I had eard about this sub before, first time here. The rumors were true and you sound like what your profile picture look like.
I'am getting trolled?

Also checked your links: 1st He did not criticised Elon for jets use AFAI can tell, it was about free speech ans stalking. (the only outrageous thing in this clip is JerryRig telling Ellon that he should not giveaway the plate of his stalker... completly out of this world biased logic, classic from Jerry.)
2nd clip is indeed related to him criticising private jet use... and so what?
Completly ignoring the context he gave in the video, ignoring all wan show where gaming jets was mentioned.
Its just banning people and comments, at first he was doing it then he said he didn't care and now he's back to banning "intentional missunderstanders".

Its like you can never change your opinions based on your lived experience and the world changing around you.

Also the plane exist, it's not about him owning it, its about how much is he going to fly with it.

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trevaftw@reddit

So you're more concerned with drama than hardware? Maybe you're in the wrong sub.

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DrLogic0@reddit

Cannot be a guy if he's that worried about another mans money spending.

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harper247@reddit

Can we ban LTT videos from this sub?

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hepcecob@reddit

What did I miss? Why ban LTT?

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Guac_in_my_rarri@reddit

comment on this sub

I'll be back with more receipts

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NetJnkie@reddit

Weird. They warrantied my backpack, just as they said they would to everyone.

The sexual harassment? 3rd party found no problem.

"Stolen" prototype? The company told them to keep it. We've seen those receipts.

Y'all need to touch grass and stop getting carried away with YT drama.....goodness.

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Vitosi4ek@reddit

The sexual harassment? 3rd party found no problem.

A third party that was paid by LTT.

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NetJnkie@reddit

Who else would pay them? Same with any audit. Financial or otherwise.

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FullFlowEngine@reddit

I guess a party with vested interest in finding wrongdoing would pay costs of an external audit (like the IRS). Which means Vitosi4ek is going to foot the bill for this one.

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skinlo@reddit

So? I take it you don't understand how independent investigations work.

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can_ichange_it_later@reddit

Its a reputable company. Its a law firm. They do this kind of shit All. The. Goddman. Time!

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FabianN@reddit

Paid to tell them the truth, so they know what further actions they need to take.

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Conjo_@reddit

LTT even made it to subreddit drama sub

oh noes how will they recover from this

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hepcecob@reddit

I thought every single one of those has been addressed. Even then, the LLT Labs testing is very impressive, did you actually read this article?

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5panks@reddit

/u/mulletarian is ready to ban one of the best YouTube channels to ever happen to /r/hardware because he's unhappy that LTT isn't perfect.

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GoombazLord@reddit

Wrong person to throw shade at

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5panks@reddit

Yeah, oops. I apologized to him and edited my comment. I think I must have mis-clicked in RES or something.

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mulletarian@reddit

What?

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5panks@reddit

I'll edit my comment sorry. I think Reddit Enhancement Suite tagged the wrong person. I was talking about /u/Guac_in_my_rarri

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skinlo@reddit

cannot accept when he's wrong

GN maybe, Linus has often apologised on the WAN show.

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stuff7@reddit

drama subs lmao

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LengthMysterious561@reddit

Is that it? If that's the worst that happened, he's done better than most big YouTubers.

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FabianN@reddit

Giving someone an item to keep, and then later changing your mind and wanting it back but not getting it back, is not getting that item stolen.

For someone concerned about facts you sure have a hard time with them.

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SomeoneBritish@reddit

Just watching the YouTube version of this and it’s really interesting.