Burst open of Diaphragm Valve.

jitukr · May 23, 2010, 21:30

I want to simulate a diaphragm valve in a pipe. Diaphragm of valve is required to burst after certain pressure and allow flow of fluid. Here what I guess, that remedy is that upto certain pressure diaphragm is wall and after certain higher pressure it has to become opening, how do I make this happen it Ansys-Cfx transient simulation in Ansys 11 or 12. Is their any other way out also? My thesis is stuck because of this problem.

ghorrocks · May 24, 2010, 06:45

You have not explained why you intend to do the simulation. What results are you looking for? Do you want details of the fracture process? Or just the shock wave which comes out of it? Do you care about the compression process before the rupture? I assume you are talking about a shock tube diaphragm, so are talking about high Ma flows.

jitukr · May 24, 2010, 21:35

Two pipes are joined with a metal foil between them acting as a diaphragm. In first pipe piston moves and compresses gasses ahead of it. Compressed gasses bursts diaphragm and enters second pipe. I need to simulate this and find flow pattern, pressure temp, velocity, choking etc of gasses thus flowing through mouth in second pipe. Flow may reach sonic velocity and shocks may also be produced. I am not able find solution to rupture of diaphragm and simulate in CFX-Ansys as transient problem. My PhD thesis is stuck.

ghorrocks · May 24, 2010, 21:40

Isn't a good starting point simply modelling the impulsive start (ie starting from rest) of the shock tube? That is, it has an initial condition and you suddenly impose a high pressure at one end (ie rupture) and this causes a high speed flow? When you have got this working well and you know how to do it properly then consider the secondary effects caused by the actual rupture process (if that is important at all).

Start simple and build the physics in one step at a time. Forget about the rupture for the moment.

jitukr · May 25, 2010, 21:50

Bursting of diaphragm is important as it is deciding factor for flow in second tube. I think that it can be solved through (first) If diaphragm is modeled as assembly of 12 circular sector and sector are fixed at periphery but meet at center. Each sector is bound at edges with each other. Each sector bends under pressure and against binding force at edges. I think Binding of components is allowed in Ansys 12 only. I am able to model Ansys-Cfx transient simulation in Ansys 11(Without bursting of diaphragm) but not very sure as how to proceed in Ansys 12.(second) I think Ansys Autodyn 12 or LS DYna allows rupture or bursting; so coupled with CFX it can be solved; but I don;t know how to work upon Autodydn or LS dyna. Are there any tutorial available for transient analysis in Ansys-CFX 12 and some tutorial on Autodyn or LSDyna in Ansys WB 12

ghorrocks · May 25, 2010, 22:39

OK - so I take it you can model this type of high Ma flow without the bursting? You had not mentioned that before. Obviously you have to be able to model this before you can add the more complex bursting issue.

Due to the large deformations in the bursting process you will need to have remeshing in there to stop inverting elements. Talk to CFX support about some demo examples of how to do this.

I have no information about Autodyn of LSDyna - wrong forum.

May 23, 2010, 21:30	Burst open of Diaphragm Valve.	#1
jitukr New Member jitukrjain Join Date: Mar 2009 Posts: 6 Rep Power: 10	I want to simulate a diaphragm valve in a pipe. Diaphragm of valve is required to burst after certain pressure and allow flow of fluid. Here what I guess, that remedy is that upto certain pressure diaphragm is wall and after certain higher pressure it has to become opening, how do I make this happen it Ansys-Cfx transient simulation in Ansys 11 or 12. Is their any other way out also? My thesis is stuck because of this problem.

May 24, 2010, 21:35	Burst Open of Valve	#3
jitukr New Member jitukrjain Join Date: Mar 2009 Posts: 6 Rep Power: 10	Two pipes are joined with a metal foil between them acting as a diaphragm. In first pipe piston moves and compresses gasses ahead of it. Compressed gasses bursts diaphragm and enters second pipe. I need to simulate this and find flow pattern, pressure temp, velocity, choking etc of gasses thus flowing through mouth in second pipe. Flow may reach sonic velocity and shocks may also be produced. I am not able find solution to rupture of diaphragm and simulate in CFX-Ansys as transient problem. My PhD thesis is stuck.

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May 24, 2010, 06:45		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,547 Rep Power: 104	You have not explained why you intend to do the simulation. What results are you looking for? Do you want details of the fracture process? Or just the shock wave which comes out of it? Do you care about the compression process before the rupture? I assume you are talking about a shock tube diaphragm, so are talking about high Ma flows.

May 24, 2010, 21:40		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,547 Rep Power: 104	Isn't a good starting point simply modelling the impulsive start (ie starting from rest) of the shock tube? That is, it has an initial condition and you suddenly impose a high pressure at one end (ie rupture) and this causes a high speed flow? When you have got this working well and you know how to do it properly then consider the secondary effects caused by the actual rupture process (if that is important at all). Start simple and build the physics in one step at a time. Forget about the rupture for the moment.

May 25, 2010, 21:50		#5
jitukr New Member jitukrjain Join Date: Mar 2009 Posts: 6 Rep Power: 10	Bursting of diaphragm is important as it is deciding factor for flow in second tube. I think that it can be solved through (first) If diaphragm is modeled as assembly of 12 circular sector and sector are fixed at periphery but meet at center. Each sector is bound at edges with each other. Each sector bends under pressure and against binding force at edges. I think Binding of components is allowed in Ansys 12 only. I am able to model Ansys-Cfx transient simulation in Ansys 11(Without bursting of diaphragm) but not very sure as how to proceed in Ansys 12.(second) I think Ansys Autodyn 12 or LS DYna allows rupture or bursting; so coupled with CFX it can be solved; but I don;t know how to work upon Autodydn or LS dyna. Are there any tutorial available for transient analysis in Ansys-CFX 12 and some tutorial on Autodyn or LSDyna in Ansys WB 12

May 25, 2010, 22:39		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,547 Rep Power: 104	OK - so I take it you can model this type of high Ma flow without the bursting? You had not mentioned that before. Obviously you have to be able to model this before you can add the more complex bursting issue. Due to the large deformations in the bursting process you will need to have remeshing in there to stop inverting elements. Talk to CFX support about some demo examples of how to do this. I have no information about Autodyn of LSDyna - wrong forum.