All of these cases have a big problem. Can you tell what it is?
If you said the intake fans are starving for airflow,
give yourself a gold star. This was a widespread problem in case design for years,
but new airflow edition cases have flooded the market,
completely solving it, or have they? See, there's nothing that Lee and Lee
or Fractal can do about users, shoving their cases right up against the wall
or on top of a shag carpet. You could be totally killing your gains, bruh.
Killing your gains.
But by how much? How much space does a fan need
before it gets starved for fresh air? To find out, we sent Adam all the way
to NASA's Langley Research Center in Virginia.
Oh, sh! To work with some of the top scientists in America
to figure out just how close is too close
for good PC cooling. And how close is too close?
For me to segue, to our sponsor.
I know how I would try to answer our question, but where would NASA start with a problem like this?
Great question. We're at the Hypersonic Test Complex
at the NASA Langley Research Center, and we're gonna do some super scientific stuff,
and that means we're using this tape and this string. I'm not even joking.
This is called tufting, and it is decidedly low-tech,
but it remains one of the most important forms of aerodynamic testing that can be done,
and it's basically where NASA starts every single time.
You see, air is difficult to study because it looks like this.
So we rely on the way it affects other things
to understand its behavior. Wow, I wasn't that far off.
What you're looking at is a Noctua NF-A12X25,
with some acrylic acting as our airflow restrictor or our panel.
With tufts or little pieces of string on the backside of the fan,
we can see how adjusting the distance of our panel from three and a half centimeters
down to just 0.5 centimeters affects our airflow.
We'll put the specifics up on the screen, and you can pause and read them.
Actually, we changed our minds. It's an article on the lab's website. It's in the description.
So what did we find out? Well, a few things.
As you'd expect, at an ample distance from our panel, our fan performs admirably,
sucking air in on one side and blowing it out the other. What I didn't expect, though,
was that the tufts near the center only started to get a little floppy
when the front panel got really close, just one and a half to two centimeters
from the face of the fan. Another thing I didn't expect was that getting even closer
caused the fan to not only blow in effectively,
but even start sucking the tufts back into the blades,
indicating reversed airflow. But it's a little hard to see like this.
Oh yeah, I forgot. These are strings they glow in the dark. We took this big-ass NASA grade ultraviolet lamp
to get maximum glow from our tufts while we recorded on this beast,
the Kronos 4K12 high-speed camera.
We're prepping our 1000 FPS 4K camera.
That's about 11 gigabits per second of data,
which means that recording on this for a minute is going to be bigger than your call-of-duty install.
And in slow motion, we can get a much closer look.
Note the increased tuft movement in our close-up test condition, indicating more turbulent flow.
And you can even see some of the tufts dragging into the middle of the fan
where there's areas of low pressure. Pretty cool, huh? Super cool, Adam, but we have Kronos camera at home.
Why did we need NASA for this? We didn't, but for what we're going to do next,
we sure did. And besides, if NASA invites you out,
are you really going to say no? They were even nice enough to give us a whole tour
that included an incredible new makerspace that they use for rapid prototyping.
Our supporters on Floatplane get exclusive access to that and a ton of other content,
so if you want to check that out, head over to LMG.GG slash Floatplane.
For now, I'll just give you a TLDR. The Langley Research Center
is kind of the OG NASA facility. In fact, it predates NASA itself,
founded in 1917 as part of the NACA, which is the aeronautics organization
that would eventually become NASA. The Langley Research Facility
was keyed in numerous discoveries and improvements to early flying machines,
creating the first hypersonic jets and paving the way for space travel
and would go on to play a key role in the Apollo missions. Currently, one of the focuses of the research center
is assisting the Artemis campaign to get to the moon as a means to get to Mars, pretty cool.
A little bit out of the scope that we're going to be working on today. So we're going to steal a couple of the 3,500 employees
that come here every day to do some more down-to-earth testing.
We're inside of the Hypersonic Test Complex at the NASA Langley Research Center
to answer that... Wait a second, this is the same lab?
Yep, same lab. I thought we were supposed to go somewhere that was like more high-tech.
Oh, it's more high-tech over there.
Oh, right, and this is Dr. Lewis Edelman. He's a researcher here at NASA,
and he's helped design all of these experiments that we're going to be running today.
Hello. So what the heck are we doing? So we've moved on from tufting
to particle image velocimetry, or PIV.
Oh. Flashing lights in fancy cameras. Sounds like my kind of deal.
First, we shine a bright light focused
into a thin vertical sheet. Then we fill the air with, you guessed it, particles
and start rapidly taking pictures. Now, that might sound like video,
but it's different in one important way. Instead of taking images at a constant frame rate,
we instead take two samples just microseconds apart,
followed by a short gap, then another two samples,
and so on and so forth. We can then use really clever math
to determine the velocity of the particles. Note that this is not speed, but velocity,
because we're talking about how fast they're going and also their direction.
Sounds simple, right? I mean, not really, but for starters,
the particles we're tracking are not air, which means that they won't move exactly like air.
Second, to do this right, we need the velocity of many particles.
That means thousands of samples across thousands of images.
And third, we need some pretty special cameras.
The Levision Flowmaster is a super high precision machine
that uses a double frame buffer to take photos just nanoseconds apart.
All right, it's finally time to test.
Hit it. So this is our first test result.
I mean, there's no obstruction on this fan. No obstruction, pure control.
So we're doing the analysis now on one image pair
as a test for the processing stream, and we go, okay, that's not very clean.
Once we take an average of the 200 or 158 images
we just took, this will fill out to look like a fairly nice picture.
Importantly, that this is kind of the hub, like we're really only looking at the top half
of the fan right now. We're looking at the top half of the fan. Would it be fair to expect that there would be,
I mean, it's a circle, so there'd be symmetry on the bottom? I would expect radial symmetry in all things
you wanna try and measure in as much detail as possible. So if we were fully zoomed out
and looking at the whole fan, we'd be wasting resolution effectively.
So this is it, applying the scaling from pixel space to physical space
from our calibration plate. Now it's starting to do the PIV,
and we can see for our 158 frames,
that's probably gonna take about 20 minutes. What is this computer running on?
This is a
i9-14900K with 192 gigs of RAM.
So this just takes a long time, is what you're telling me. Yes. After considerable number crunching,
we've got our results, and what you're looking at is a narrow slice of air
that is flowing out of the fan. The colors indicate the stream-wise velocity of the air,
so how fast it's going away from our fan blades,
and then the arrows are kinda just an easier way to visually process that same information.
Then to make it even simpler, we added these dots. Without a front panel, flow is smooth and fast moving.
There's a small section where you can see there's no flow, but if you look closely,
that's right behind the fan hub where there are no blades.
Now, it is important to remember that this is just a thin slice of the overall airflow
in what is a 3D space. Our test isn't gonna capture
the spiraling 3D vortex of the air, but the overall direction away from the fan
is what's most important for cooling, so this is good enough for our purposes.
Fun observation, by the way. Dr. Edelman noted that the way that Noctua's fans
throw momentum inward more than a typical fan contributes to reducing their overall noise.
Good job, Noctua. When we move the plate closer, we don't see much change.
That is, until, just like in our Tuft test,
we get as close as about 15 millimeters. Take a look at how large our dead zone has become now.
We also noticed that the flow of air is starting to curl outward
rather than coming straight out of the fan. What that means is lower stream-wise momentum
to blow air across your components or to pass through a restrictive heat sink or radiator.
But why? Well, it's due to the difference in radial pressure.
The air that passes through the tip of the fan blades is lower pressure and almost bounces off the stagnant
and thus higher pressure air that's right by the fan hub.
This isn't optimal, but our overall airflow
is still pretty good, so for a case fan,
it's probably still fine to have this much restriction. We will check on this test condition again later
once we add a radiator. For now, let's look at our worst case scenario in open air.
Imagine your case is right up against a wall or your power supply intake is on the floor on a carpet.
This is what you're doing to your poor, poor PC.
Not only is the fan barely pulling any air in at the edges,
it is so starved for air that there's a reverse flow
that causes the air to curl into a vortex that isn't gonna move heat anywhere
and that's your best case scenario. What if we were trying to cool something directly
with our starved fan? To find out, we whipped out a water cooling radiator
to create a scenario with much higher back pressure. You can think of back pressure as the friction
that a fluid experiences in movement, and as you can see, adding a ton of friction
to an already restricted fan results in a two-word review of my debut rap album, Zero Flow.
Now naturally, backing this off to a 15 millimeter gap yields much better results,
but it's still worth noting that this is a massive drop in performance compared to our free air test,
especially with respect to the size of our dead zone over the fan hub.
Practically speaking, we're only getting flow on about the outer 50% of the fan blades.
Interestingly though, the radiator completely straightens out the flow
and we don't see that same outward curling, but the speed is cut about in half.
So what does all of this mean? Well, we can't draw overly broad conclusions.
We only tested the NFA 1225 at full speed, but it seems like you can get as close as about 15 millimeters
or a little over half an inch from your fan with reasonable performance.
Any closer and you are seriously harming its cooling ability.
An obvious question would be, why go to all this trouble?
Couldn't you have just sent a piece of acrylic and a fan to Cybernetics to put in front of their fan tester?
Well, yes, but also no. While a fan tester would tell us the performance
of the fan under various conditions, we were more interested in measuring the behavior
of the air, which tells us not only the answer,
but it also lifts the veil on why the answer is what it is.
It also gave us an excuse to check out another really cool piece of kit down in Virginia.
If you thought air was complex, we'll just wait till human perception gets involved.
Yeah, we're gonna talk about sound. Now, we have been hard at work improving
our audio testing at LTT Labs. I mean, we even just built a home theater room
to test more speakers now. But what we don't have is a NASA grade audio chamber.
This is the shack and it's a little old place where we can do some testing.
The small hover anechoic chamber was constructed in the late 80s and it gets as quiet as 18 dB,
which is disconcertingly quiet.
For our testing today, we're using two different arrays, a linear one up there and a spiral one.
Why are they different shapes? Well, they have two different jobs. The linear array is a directivity array
that gives us a broad idea of where sound ends up in the chamber.
The spiral array, also called a phase array, is a collection of 40 beamforming MEMS microphones
that allows us to get super detailed information about the source of a sound.
These microphones are so precise that we can map the location of the sound
onto footage from the camera that sits in the middle of the array.
Essentially, you can define a region in here and it will perform an integration.
So right, it's a little hard to see, but right now it's just region one, two, and three.
And then you can basically go ahead and have it process it and give you a spectrum like this
with the different contributions of those regions to the total sound field,
or at least what their array picked up. Why would folks at NASA need to know this kind of stuff?
Well, when they're testing the acoustic properties of something, they want to know where that sound's going to be coming from.
Like this, for example, they might want to understand if the sound is coming from the tips of the blades
or if it's coming from the rotor itself. There's only one way to find that out,
and that's to use the phase array. I mean, there's probably another way to find out,
but the way we're going to do is the phase array. So stop asking questions.
Well, you can ask one more question. If you noticed, our fan is looking a little pink.
Why would folks at...
That's because this apparatus was designed to test rotors for things like drones.
So our NF-A12X25 that we were using before,
it was a bit too quiet, and we swapped it out for this industrial version
that runs considerably faster and considerably louder. The paint that's on it is this funky pressure sensitive paint
that we were going to use for another test, but we ran out of time
because NASA has a lot of important work to do. Anyway, I bring up the paint
because it might make the fan perform a bit worse than what Noctua would ship from the factory,
but we aren't comparing it to other fans. We're only comparing the intake clearance,
so we're not worried about that. Again, because of time constraints, we decided to just test the fan without the front plate
and at the 15 millimeter point. Now, intuitively, you might think that covering a fan
would decrease the amount of noise that it makes, right?
But if you've ever tried placing your hand in front of your PC fan, you might have noticed that it often gets louder
up until the point where it becomes completely started there. And in our test conditions, that's true.
You can see a broad spectrum increase in noise when the front panel's present.
Why? Well, referring back to our PIV results,
remember the stalled flow in the middle? That causes the overall airflow to be more unsteady,
which makes it louder. Think of it like roaring rapids
versus the smooth flowing water in the Mississippi Delta.
And this increase in noise also shows up in our phase array results.
Yet another reason to not let your fans get too close to obstructions.
Even if you have cutouts in the side panels, those can still cause annoying resonances.
Fractal terra owners will know this very well. In summary then, for performance,
keep your fans more than 15 millimeters away from any surfaces and 20 millimeters or more
if you're gonna be contending with other obstructions like a heat sink or a radiator.
As for noise, it seems like you can't have too much clearance from the intake,
but you can definitely have too little. There are a hundred other questions
we would have loved to answer, but frankly, NASA was already extremely generous
with their time and they are hard at work answering much larger questions.
This may not have been the be all and end all answer that you were looking for,
but that's just how science is. It's the accumulation of many tiny discoveries,
solving many tiny mysteries that build up to create a knowledge base that allows us to
have a greater depth of understanding of the world that we live in.
Before we go, I wanna thank all the folks that Massa, who helped made this possible,
Lewis, Brittany, Nick, Jordan, so many more folks that I haven't named
helped make this trip possible. Thank you so much. Thank you for watching and of course,
thanks for the segue to our sponsor. Thanks for watching.
If you like this video, why don't you watch another one of our videos where we tour some cool place,
like how about there's an internet exchange in Toronto
that was pretty dang neat. Thanks again to NASA. Thanks for watching.
Bye.