Water tank reactions

[pegus]

Good day,

We have a pressurized volume under water inside a tank. This tank is half filled of water. We know the pressure level of the enclose volume. I wonder if there is any way to simulate the sudden decompression of this pressurized volume. My intention of this analysis is to obtain the reaction loads the tank will receive when this sudden decompression of the volume occurs. I was looking for a multi-phase analysis, but I haven't find how to model this problem. Please let me know your thoughts or what topic should I research about it. I am using ANSYS R1.

Regards,

P.P.

 

[rb1957]

you've got a pressurised tank under water inside an enclosure (a larger tank) ? (that's how I read "pressurised volume")

it sounds like something you can solve with FEA. I'd research "modelling explosions" and "sudden decompression".

is the larger tank (1/2 full with water) enclosed ? I think so as you "know the pressure level of the enclosed volume".

another day in paradise, or is paradise one day closer ?

 

[pegus]

Thanks for the reply,

Let me explain the scenario a little bit more. We have the pressurized volume, lets call it "tank 1", this volume is pressurized with air. Tank 1 is inside tank 2. Tank 2 is half filled with water and it is at ambient pressure. tank 1 is under water while is inside tank 2.
In am wondering what reactions will tank 2 will take in case tank 1 fails. I know that during an impulse load the water will transfer the load from the decompression of tank 1 to tank 2. But I want to explore the option of modeling in ANSYS.
I hope this explanation helps.
Regards,

P.P.

 

[rb1957]

yes, that sounds like "a pressurised tank under water, inside a larger tank".

the biggest question is whether this larger tank has a lid on it. If it's open, then water will slosh out and the forces will be reduced and there'll be an imbalance of force from the decompression.

Modelling decompression is quite well understood, maybe more a CFD problem than a FEA.

An imponderable issue for you is "how does the inner (pressurised) tank fail ?" does it …
1)"de-materialise", so the pressurised air expands in all directions at once,
2) does it cut itself in 1/2, around the circumference ? along the length ?
3) does it "leak" into the water ?

another day in paradise, or is paradise one day closer ?

 

[pegus]

Good day,

it is a horizontal cylindrical tank, the door is one of the caps. it has a vent area on the top of the tank.

Regarding the failure method, most of the cases is that one of the welded edges fails. But I believe I would like to model the worst case, which I believe will be 1) from your enlisted cases.

Regards,

P.P.

 

[rb1957]

1) seems to be the easiest to analyze … start with your water containing a high pressure bubble, and start the clock …
the high pressure air will expand (almost spherically) and "interact" with the water, etc

another day in paradise, or is paradise one day closer ?

 

[pegus]

Is there a way to model a bubble in CFX ANSYS? I am using ANSYS R1.I have performed pressure drop analysis on pipelines and manifolds. But not familiar with a bubble. If you have any reference source in where I can research more about, I can take a deeper look.

Regards,

P.P.

 

[rb1957]

sorry, not a clue … try YT or ANSYS manuals/tutorials/helpdesk.

another day in paradise, or is paradise one day closer ?