Flared Ports Part 2

[Collo]

About 6 months ago, I posted results of testing flared ports for turbulence.
The discussion ran for 6 pages in the following thread:
Flared ports and turbulence

That work described how increasing flare size allowed a higher velocity to be used before turbulence became audible.

Since then, I've built some larger boxes and more ports, allowing me to discover where this effect "rolls off" as "core" turbulence takes hold. Additionally, I've found that port performance varies with frequency.

All the findings, along with a much improved "Flare-it" calculator can be found at the original URL:
http://www.users.bigpond.com/bcolliso/index.htm

I hope you all find it useful, and I look forward to the discussion...

regards
Collo

[Collo]

whoops,

that link is to the homepage

the one for the tests is:
http://www.users.bigpond.com/bcolliso/flare-testing.htm

Collo

[paulspencer]

Great work Collo!

[Collo]

Thanks Paul,

thanks for that comment.

Here's an example of how the new calculator can be used .....

In the original thread you asked:

Can this be right? I entered a 100mm vent with 72mm flare radius and it says 42.9m/s is ok!!!

my best answer at the time was:

There is of course the principle that the unflared section of the port also has a speed limit.

"Flare-it" now provides a much better answer:

The limiting velocity for a 100mm diameter port is 29 m/sec @ 30hz, and 19 m/sec below 25hz.
To control boundary turbulence up to these velocities, a 44mm flare is required - there is no advantage in going any larger!

Regards
Collo

[phillfyspoon]

cheers your programs are of great help

[phillfyspoon]

Hi collo Could I have a chat with u on msn my addy is phillfyspoon@msn.com

want to talk about flares

[Collo]

Done. That MSN Messenger makes things so easy.....

[phillfyspoon]

hi collo

Im poor at maths could u workout what mold i need to heat mold 25mm flares on a 6inch port

[Collo]

Cut three MDF disks to the same size as the internal diameter of the pipe. Screw the first disk to a baseboard. Screw the next disk to the first one, end then the last one to that.

I usually calculate the exact size of the disks to minimise the amount of filler required, but for a 25mm flare, the savings are minimal.

Cut a 25mm disk from whatever material you have available to use as a scraper.

[phillfyspoon]

Hi Collo

Been alittle busy but got everything I need

I found something that might act as a mold for me but does the shape of the flare matter?

this is what the shape will be like: