Aircraft Fuselage Decompression 2

[AeronauticalBG]

Hi,
I am trying to find what would be the load on Aircraft Bulkhead during A/C decompression. It looks like a fluid mechanics problem. Any suggestions will be highly appreciated.

 

[IRstuff]

Not sure how that's different than when it's not during decompression.

TTFN
faq731-376

 

[rb1957]

decompression analysis is a fluid dynamic problem ... a volume of air being driven by a differential pressure through a small opening.

since we're talking bulkheads, this implies a divider between two compartments. so you've a couple of scenarios ... one volume (larger or smaller) decompresses first, and the bulkhead is loaded by the other compartment (smaller or larger) which has only partially decompressed and continues to vent into the first compartment.

 

[AeronauticalBG]

Thanks rb1957. My approach is using the Conservation of Energy Bernoulli equation and also the low of conservation of mass. Once we have decompression, the pressure from one side of the bulkhead will start droping with curtain rate, but the pressure from the other part of the bulkhead will start droping as well, but with smaller rate (here, both pressures are related, but don't know how). If I could find the pressure droping rate p1 and the other p2, which would be function of dt, that pressure differential would give me the load on the bulkhead for that specific time frame. Do you think rb1957 I am on a right track? Thank you again for your respond. Cheers,

 

[rb1957]

it is a complicated analysis. you start with both compartments at the same pressure, and then one compartment punctures itself and starts to decompress. as this compartment decompresses, air will start to flow out of the other compartment.

as you need to define ...
1) the puncture ... area and flow rate out into the atmosphere, and
2) the airflow (areas and flow rate/discharge coefficient) between the compartments.

some things come into play ...
blow-out panels ? (will limit the differential pressure and vent(rip apart) the two compartments)
access doors ? typically doors will close against an angle, or structure, so that the extire edge of the door is supported and the door would probably remain effective. but for pressure acting in the other direction (pulling the door away from this support) the only thing working is the door latch. if you've happened to have ordered a silly plastic latch (like we did) and you have to "show it good" well, the latch will work like a blow-out panel and fail (in a "controlled" manner) and limit the differential pressure ... ie the latch will probably fail, the door would open, and limit the pressure differential.

 

[WKTaylor]

AeronauticalBG..

Suggest You start with SAE AIR 5661 Compartment Decompression Analysis



Regards, Wil Taylor

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

 

[AeronauticalBG]

Wil, how worth it is to go buy SAE Air 5661 - it is not that expensive, but what I mean, is it really related to my problem? Thanks,

 

[WKTaylor]

Take a peek at it

http://standards.sae.org/air5661

Also available on IHS standards Expert if You have a subscription.

Regards, Wil Taylor

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.