gas whistling while passing
gas whistling while passing
(OP)
Hi there !
hope someboby can help me.
I have a problem with some gas flowing in an header.
The gas flowing in the header is generating a whistle
I was wondering: is there a formula relating gas velocity to the whistle ?
May this whistle be related to tube diameter, too ?
May this be related to tube lenght ?
One important detail is this: the gas comes into this tube from a bigger tube, having a section that is 4 times bigger than the same tube.
The ratio of the two diameters is 2.
many thanks !
hope someboby can help me.
I have a problem with some gas flowing in an header.
The gas flowing in the header is generating a whistle
I was wondering: is there a formula relating gas velocity to the whistle ?
May this whistle be related to tube diameter, too ?
May this be related to tube lenght ?
One important detail is this: the gas comes into this tube from a bigger tube, having a section that is 4 times bigger than the same tube.
The ratio of the two diameters is 2.
many thanks !





RE: gas whistling while passing
I calculated the gas velocity, that is 45 m/s
this means we have a Mach number of 0.13.
Thanks for your help
RE: gas whistling while passing
Your whistling could be piping configuration (two elbows out of plane sets up some interesting flow patterns that make noise) or a (planed or unplanned) restriction in the pipe, or gas blowing over a dead leg. I haven't seen a simple step down in diameter turn a quiet system into a noisy system, but don't see anything that would prevent it.
The only field of science that is less well defined than fluid mechanics that I know of is acoustics. I would be really shocked if you came across a reference from piping configuration or fluid velocity to sound frequency.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. ùGalileo Galilei, Italian Physicist
RE: gas whistling while passing
RE: gas whistling while passing
I'm sure you are not looking for a single cut-off point. You need to know at what velocities the noise increases from silent, to a whisper, to a whistle, a scream and finally a roar. In a typical HVAC handbook I found the recommendation that air conditioning duct velocities should be kept below 7 m/s in domestic and office environments. This should give you an indication of when the "whisper" point is reached.
Some very useful recommendations for water velocities in various environments were given by DRWeig in thread378-348061: Maximum Velocity in Piping Systems
The size reduction is also a likely source of noise. When a fluid flows through a standard pipe reducer (big to small direction) the fluid continues to converge after the narrowest point in the pipe forming the "vena contracta" where the local velocity could easily be double the calculated average. After the vena contract you have all sorts of eddies and turbulence which could also initiate your whistle. Replacing a pipe reducer with a very slowly converging conical taper may help the situation, but I suspect that your 45 m/s is too high anyway.
Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: gas whistling while passing
I am here attaching you the description of the tubes, with velocities and dimensions
I would be grateful if you could help me
@mr katmar
Many thanks
I am starting to think that the phenomena may be due to following elements
- high gas velocity
- sudden contraction
- possible cavitation ?
I am wondering: is there a number that I can correlate to a cavitation phenomena ?
Thanks !
RE: gas whistling while passing
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. ùGalileo Galilei, Italian Physicist
RE: gas whistling while passing
PLease, may I ask you if you have any experience concerning this whistiling phenomena ?
Have you ever faced to something similar ?
Many Thanks
RE: gas whistling while passing
Try uploading your sketch again, no cigar this time.
The issue is common where branch connectons are encountered.
RE: gas whistling while passing
hope it works now
thanks in advance
RE: gas whistling while passing
Best regards, Morten
RE: gas whistling while passing
Interesting to see the velocity increase in the small diameter piping. First you need to carry out your flow analysis and identify the various pressure drops in your system.
Once you've done that, there are noise estimating procedures available in the technical literature.
Good luck,
RE: gas whistling while passing
RE: gas whistling while passing
given that 45m/sec would be colloquially referred to as "whistling along", it is not surprising that you've got issues. If the contraction is a sharp edge like you show it will not be good. You could try a much smoother or longer reducer to reduce the turbulence that must be occurring.
Any good reason why it is going at this velocity?
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: gas whistling while passing