Hi folks,

I want to know the impact of a detonation on a distant structure. So i guess i have to model the unsteady propagation of the shock wave generated from the detonation. Can anyone suggest me how to go about it in Fluent?

Thanks in advance,

Regards, Maddy.

first off all, you have to think how you will generate your shock wave and than you have to think about the media of propagation(probably air). you can start thinking in a cube, dont need to be the real situation, and from one side of the cube you make the energy for the propagation of the shock wave.

Dear Pacheco, Thanks a lot for the response. Yes, the medium of propagation is air. I have no idea on how to generate the shock wave. Can u kindly suggest me to some reference. I have tried to simulate a hallow cylindrical space with Pressure inlet BC and Pressure outlet boundary in Fluent. But it is diverging all the time. I have used SA model with coupled implicit solver. Kindly suggest me some direction. Thank you, Maddy.

[ssixr]

hello maddy,
gud to know tat someone is working on detoantion wave like me....have u succeed in creating detonation wave?


sudhir

[Alan]

I would start by creating the rectangular domain as previously mentioned. You will need to know how far away the origin of the blast wave is from your structure. You will also need to know the initial conditions of the explosion. Then what I do is set up my mesh so I have two domains - the domain under examination (the rectangular domain initially created) and a much smaller domain representing the initiation of the blast wave. This could be spherical or cylindrical - depending on your geometry. You would then patch the blast wave initial conditions into this second domain and run a transient simulation. The blast wave will expand and relax over the course of the simulation, and propagate to your structure under examinaton.

[ndabir]

Hi Maddy,

Did you solved your problem? I am dealing with some similar problem. In fact I am not interested in generation of shock wave but I just want to simulate the propagation of shock wave in air and also in water. I use a high pressure and temperature as inlet (which is a very small sphere) and an atmospheric pressure as outlet (a much bigger sphere). But my results are not reasonable. Could you please tell me what kind of solver did you use and what did you assume for inlet conditions?

[hesamking]

I think the best software for your works are Ls-dyna and Abaqus.
I am a beginner in Ls-Dyna but I know it has the ability of doing all kinds of blast simulation and its interaction with structures or human body.
Also I have seen in several papers the use of Abaqus for this end.
The Ls-dyna has recently included CFD capability to its system.
Just forget about Ansys or Comsol. These gys are much more user friendly and specialized.
Good Luck!
Hesam

[sfotovati]

If you want to check the shock effect, also take a look on Ansys-Autodyn. fr these cases, Explicit-Dynamics works well. You can assign any pressure or velocity, or even an explosive itself, to model the detonation.

[hesamking]

Dear sfotovati,
Actually I am interested to see the flow dynamics of the blast waves. I am currently working with Ls-Dyna that is very similar in nature with Auto dyne and follows an explicit scheme. I have successfully modeled in Dyna but I want to do the CFD which I have to do in CFX or fluent.
any ideas?
Thanks,
Hesam

[Calmly]

Which turbulence model would you recommend for a blast wave propagation simulation?

I know the thread is old but i'd like to hear your ideas

[yorelchr]

hello,

I know that these posts are quite old but I am dealing with the same situation (modeling blast with FLUENT) and I don't have reasonable results: I have a room and inside this room, a small sphere. I have done a patch on the sphere, very high pressure and a patch at atm pressure for the room. I use density-based solver.
My question is: do I use ideal-gas or incompressible ideal gas? and for operating pressure, should I put it to 0 or let 101325Pa?

thanks in advance for your help

[LuckyTran]

Originally Posted by yorelchr

My question is: do I use ideal-gas or incompressible ideal gas? and for operating pressure, should I put it to 0 or let 101325Pa?

Use ideal gas. The incompressible ideal gas law takes the operating pressure and allows density to change only with temperature. Clearly for a detonation wave, this is not an appropriate EOS.

The operating pressure is quite arbitrary (unless you are using the incompressible ideal gas law). You can set it to just about anything as long as you remember that all pressures in Fluent are gauge pressure. There are some advantages in truncation error if you specify the operating pressure closer to the mean pressure. Whatever you set the operating pressure to, remember to correct all other pressure settings to get the desired absolute pressure. If it is too much of a headache then you can use 0 Pa for the operating pressure and interpret the pressures in Fluent as absolute pressures.

[hanguyen]

Dear yorelchr
Did you complete your model for simulating the blast load in FLUENT?
Could you guide me how to make a patch from the sphere?
I read the reference "Using Computational Fluid Dynamics (CFD) for Blast Wave Propagation under Structure". They mentioned abou this, but I still do not know how to do it
Thanks in advance.

Originally Posted by yorelchr

hello,

I know that these posts are quite old but I am dealing with the same situation (modeling blast with FLUENT) and I don't have reasonable results: I have a room and inside this room, a small sphere. I have done a patch on the sphere, very high pressure and a patch at atm pressure for the room. I use density-based solver.
My question is: do I use ideal-gas or incompressible ideal gas? and for operating pressure, should I put it to 0 or let 101325Pa?

thanks in advance for your help

[NAVEENRJ226]

Originally Posted by hanguyen

Dear yorelchr
Did you complete your model for simulating the blast load in FLUENT?
Could you guide me how to make a patch from the sphere?
I read the reference "Using Computational Fluid Dynamics (CFD) for Blast Wave Propagation under Structure". They mentioned abou this, but I still do not know how to do it
Thanks in advance.

Dear Hanguyen,
have u completed your model for simulating the blast load in Fluent.I am also working on the same problem.