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André June 19, 2002 09:03

Pressurewave from explosion
 
Dear Fluent users,

Has anyone of you got information for me about modeling the pressurewave occuring after an explosion? We do not want to simulate the explosion itself, but only the pressure produced by it.

Many thanks in advance.

Evan Rosenbaum June 19, 2002 13:27

Re: Pressurewave from explosion
 
Please clarify your question. Do you want to know how to specify a pressure pulse in FLUENT, or how to determine the pressure pulse that would result from a specific explosion type/size?

André June 25, 2002 02:52

Re: Pressurewave from explosion
 
Dear Evan,

The first one is the case: we want to specify a pressure pulse to design equipment for releasing the pressure. But the information we have concerning the explosion is limited so information about pressure pulses for different types of explosion is welcome aswell. People at Fluent allready indicated that patching in a (very)high pressure in a small area would be a way to model this.

Thanks in advance.

Evan Rosenbaum June 25, 2002 13:14

Re: Pressurewave from explosion
 
Andre,

The pressure pulse will be a sharp (nearly linear) pressure rise fom ambient to the peak pressure followed by a slower pressure drop back to a low pressure (neglecting any blast-wave reflections). The final pressure may be lower than the pre-blast pressure, depending on your exact conditions.

If you geometry allows, you may be able to use a pressure inlet in the model and specify a time-varying pressure spike. If not (i.e., explosion within a tank of vapor or similar) you can patch the pressure directly into some cells.

Evan

steven June 25, 2002 22:06

Re: Pressurewave from explosion
 
hi,all as i know,pressure is assumed to be constant in the premixed turbulent combustion.but pressure can be variant in the case that gas/air is ignited in the tube? Can that quietly gas/air in the tube may be ignited at the end of tube be modeled by premixed turbulent combustion or species transport eqution? thank you sincerly


steven June 26, 2002 03:03

Re: Pressurewave from explosion
 
hi, i'm simulating gas explosion in the tube ,one end of tube is close,and another end is open,gas/air is premixed before mixture is ignited.then quietly gas/air is ignited in the tube which end is close ,this case can be modeled by fluent species reaction or premixed turbulent combustion? thank yousincerly

steven June 26, 2002 03:06

Re: Pressurewave from explosion
 
hi,all i'm simulating gas explosion in the tube ,one end of tube is close,and another end is open,gas/air is premixed before mixture is ignited.then quietly gas/air is ignited in the tube which end is close ,this case can be modeled by fluent species reaction or premixed turbulent combustion? thank you sincerly

Lanre June 26, 2002 10:30

Re: Pressurewave from explosion
 
Yes. You'll need to use the the finite-rate model using either the segregated solver or the coupled solver for your detonation problem.

steven June 26, 2002 22:12

Re: Pressurewave from explosion
 
Dear Landre:

thank you!

because gas/air mixture is so small in my problem,and L/D(tube)is so small,it belongs to deflagration case.in order to simulate the case of spark ignition, i patchs pressure and temperature in a small cells,but it often wasn't coverging,can you tell me why ? in addition,it seems that fluent's three combustion model must have the velocity,doesn't it? thank you in advance steven


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