Dimpled Precision Ports

Do Dimpled Precision Ports show any real increase in performance?

According to some reputable fluid dynamics researchers, dimples placed in the first 5-10% of an air flow obstruction CAN extend laminar flow regions (less turbulence). Specifically, Texas A&M has a few profs that are VERY well funded by NASA/various government and military sources.

Theoretically, dimples placed at very specific locations will nucleate small, well-organized vorteces that stay separated, and never grow to turbulent flow. In normal "smooth" wall flow, randomly generated vorteces will usually build up to turbulent flow, even at speeds well below the speed of sound (port noise speed).

These small vorteces give naturally occuring flow imperfections a place to go. Flow won't be perfectly linear, but it's well organized and laminar for up to 60% of the flow surface (big improvement). That corresponds to a decrease in friction of ~20% (also a big deal).

Does air plane tech apply to subwoofer tech?

Pic of DPP:

well you know how to find out. if they are making the ports that way then they problem assume they work lol

i was hoping no one else would notice these are out as im going back to boxes with aero ports next year

i bet its .3 or less if it changes.

ive alway wanted to try a whole box like that.... hell thats why golf balls are made like that better air flow

kickercrx wrote:

i was hoping no one else would notice these are out as im going back to boxes with aero ports next year

*accepts the shame*

Alan, do you know if anyone has atleast qualitatively verified if the effect is positive or negative, compared to normal aeros?

I know it reduces the joy of experimenting, but I'd rather not spend college loan $$$ that taught me the fluid mechanics.

@ Rowlands, it's probably a waste to dimple the whole box. Anywhere that has a high-Reynolds Number flow (near speed of sound) can benefit from controlling the turbulent transition. Box walls should be silky smooth, but corners and edges (as you know) are places where rounding/45's are many times worth the effort. If you can organize the flow and prevent turbulence, a box "should" be more efficeint.

Never saw the aero port design but I have seen the slot port one an wasn't gonna say anything till tested an proven. Good luck though.

Alan wrote:

i bet its .3 or less if it changes.

i have lost by .3 or less before lolololol

anywho, we thought of this before, not ports, but boxes, heck whole cars, but that'd be way to time consuming, heck we even layed alum foil and resin the cargo area floor of a crx hoping it'd be more slick or whatever, that didnt gain anything

From what I have read, this phenomenon only occurs at a very narrow range of air speeds (such as golf ball speed). I have no idea what port velocities are, but if they are in the region of golf ball speeds (100-200mph), then they should certainly help. Of course, that theory took a hit when Mythbusters showed an increase in mpg when they dimpled a whole car, so it could be effective at lower velocities, but if it were effective at higher speeds, then I can guarantee we would see fighter planes with dimpled skin. You would probably need the entire port to be dimpled to really see any gains though and not just the flares.

But wth do I know?

what i gather from what chris is saying is that enclosure walls and the inside of the port has no where near the pressure as the bottle neck created at the opening .. where the dimples are much more effective.. correct?

I hear ya, but what's the point of speeding it up with dimples only to slow it down and disrput the laminar flow when it hits the smooth skin of the tube? Could be a zero (or negative) sum gain if the entire port isn't consistant.

makes sence.. i dunno.. lol

I'm all about testing. I'll order some and let you guys know.

Or will I

If they had a 6" dimpled I'd buy it to test. Can't fit two 4s though

so how much are they and where do you get them? if they arent that expensive ill get some and see what difference there is between these and the regular ones!!!

On a similar topic, FastSkinz is a "golf ball" style vehicle wrap, which claims 15-20% fuel economy savings... which was debunked by Popular Mechanics.
Link!

The FastSkinz marketing is pretty lame, citing theory that you learn in the first week of Fluids class... but it does reinforce the idea that strategic placement of items that will "trip the turbulent boundary layer" may offer some reduction in drag.

The problem with FastSkins is that they air flowing around the car is not moving that fast... 50-70 mph + wind speed. Tiger Woods has golf ball speeds reaching 180-200 mph + wind speed. The skin friction on a golf ball is MUCH higher than a car. As Ford notes in the PM article liked above, the primary drag mechanism for cars is vehicle shape.

Port velocities can get fast, something less than sonic flow (760 mph) if you restrict the port area too much... but it won't see those speeds in monster walls. So, to maximize port efficiency, you have two choices, use plenty of port area and smooth the transitions (corners, edges, port walls)... Think S-10 box. Or in "restricted flow" conditions, you also need to prevent widespread turbulence (energy loss)... like what aero ports do for CRX or SUV boxes.

TaylorFade wrote:

I'm all about testing. I'll order some and let you guys know.

Or will I

I know a certain mini vehicle we can try them in...