Dimpled fan blades REDUCE turbulence!

[jonnyGURU]

I originally saw this in a Tagan PSU:

http://www.zaward.com/products_index02.php?Cid=1140

The fan blades have dimples on them, like a golf ball.

But golf balls have dimples that CREATE turbulence and gives the ball lift and decreases drag.

But does it make the golf ball QUIETER?!?

I like these fans because the can start with only +5V and actually come with a power adapter that lets you tap +12V or +5V of the power supply. They also come with rubber isolating mounts.

But let's look at the specs for the 120MM....

@ 12V, 1500RPM, the fan moves 57.6 CFM and ~24 dB.

My typical 120MM fan @ 12V is 1700 RPM, moves 64 CFM and is 29.78 dB.

Am I wrong in thinking if I lowered the voltage on my current 120MM so the RPM is only 1500RPM that it might be pretty much the same CFM and dB?!?

I'm curious if these dimples really help these fans. Unfortunately, I can't find any reviews of these fans. Anyone ever hear of these or use these?

[kwak]

they look very similar to the sharkoon silent eagles tested here:
http://www.madshrimps.be/?action=getarticle&number=2&artpage=2152&articID=516

[jonnyGURU]

Interesting. So Sharkoon sells them at two different RPM's, 1000RPM and 2000RPM, instead of Zaward's 1500RPM.

It's definitely the same fan. They're all made by GlobalWin.

2000RPM is pretty damn fast for a 120MM fan. No wonder it's 63.2dB at close range. Too bad they didn't report the RPM's so we know how fast it's spinning at 7v and 5v.

I know the Zaward spins at 700 RPM at 5V, and at that speed it's less than 15dB, but only moves 27.5CFM. They report the 1000 at 37.8dB at 5V, but that's at close range. I wish they did the sound tests at 1m as per industry standard. :(

[GalvanizedYankee]

http://www.provantage.com/arctic-acf12~7ARCT005.htm

On topic: Yes, I read reviews about 18 months ago on the Sharkroon 80x25.
Looks good in white with dimples but won't be easy to wipe clean. They reviewed well.

My Sanyo Denki 120x38 #109R1212H1011 drive 103cfm@12V@39dBA and start/run reliably at 4.75V, so 5V is killer driving about 48cfm in near silence.
I do not lie as there are several that will back me up on this one ;)

[jonnyGURU]

Thanks GY, but I'm not looking for a replacement fan. ;)

I'm just being inquisitive about the "dimple design" and how it supposedly helps reduce wind noise.

[GalvanizedYankee]

In my teens I raced outboard hydroplane boats...Yeah baby! We built our own boats.
The nails used for the bottom were set with a large(1/2") convex punch. This gave a very slight dimpling and the boats would break away from the water much faster than a smooth bottomed boat. They didn't hook as easy either (grab as the boat turns).
I think the dimpling keeps the air from clinging to the fan blade and not shearing as it comes off the blade. Kind of like a spoiler at the rear deck on a car. Not a wing forcing the car down, just a lip that breaks up the air.
Make any sense?? :)

[GalvanizedYankee]

I had a dream about this thread last night so I back. :D

http://www.soton.ac.uk/ses/outreach/greenpower/boundarylayers.html will cut right to the chase. Used on these low speed fans, I doubt it makes that much of a difference. But I'm old and my hearing of high frequencies is pretty lame.
For further info search, fluid dynamics sites, laminar air flow or more boundary layer air flow.

Tid bit: The single longest lasting piece of engeneering that the Wright Bros. did was design the propeller as a rotating wing. Thier design was 83.5% efficient, considered decent even by todays standards.

Intake ports on very high performance 4 stroke naturally asperated engines are not smooth but nubbly, kind like this Sharkroon fan blade. The dimples are oblong however. This helps break up the slow moving boundary layer of air and helps keep the fuel in suspension. F1 engines have intake port velocities of about 550fps. At 610fps a sonic wall is hit and flow stops because of the reflected sound wave reaches the sound barrier.

[jonnyGURU]

I liked you analogy better! :D

[Skott]

Cant say I have ever heard of a noisey golf ball so must be dimple quiet. :D

[SixIron]

Hmm. I have a Zalman 400 watt PS but I've never had the need or inclination to inspect the fan for dimples. Perhaps I should whack it with my 6 Iron? lol

Edit: Oops, Zaward ain't the same as Zalman.

[jmke]

I wish they did the sound tests at 1m as per industry standard. :(

at 1m all fans would be hardly audible over ambient noise, without a special anechoic room to keep noise out, these dBA readings I do are for direct comparison only...

last time I checked, anechoic rooms don't come cheap, more expensive than a decent PSU test setup ;)

[kwak]

not really, look at spcr, they do measurements at 1m, and with their measurements, even a nexus(at 12v), is audible, so pretty much any fan will give you a measurement.

[beavis88]

Cant say I have ever heard of a noisey golf ball so must be dimple quiet. :D

If you're standing near someone who can really mash a golf ball, and especially someone who puts a lot of spin on the ball, it makes a really pronounced "whoooosh" noise while it flies :)

[Skott]

Ever notice though you never hear the ball hit you? It just does. Or if someone yells FOUR! you never hear or see the ball till it lands? Maybe on take off you hear them but once they get going its stealth in the sky. :lol:

[Bbq]

Are you recommending that they make fighter jets in golf ball shapes now? it would be hillarious. Imagine Kim Jong golfing his perfect score while inventing an ipod, and then a "hey why is my golf ball going back towards me?"

[kimandsally]

I would think if they were any good the guys at SPCR would all be using them, I rate Mike Chinn he's like Jonny Guru he says it as it is.