Igniting mixture

Prateek garg · December 19, 2012, 04:44

Hi Friends,

I am trying modelling DDT (deflagration to detonation transition).
My first step was to create a uniform mixture of Jet A vapor and air which I have done successfully.
During my second step I want to ignite this mixture to model DDT.
While doing this I made a new case file. in this new file I changed the air and fuel inlets into wall, made a high temperature primitive region (to initiate ignition) and defining the reactions. While defining run I am using the result file of the previous simulation (mixture formation) trying to run it but it always end up with error. once it end up with Stack overflow then I reduced the time step. but it again stopped with error.
For new simulation I am taking time step size as 10^6 sec and time duration of .001 sec. but still there is an error.
Can someone tell me If this is the right way to go or what could be the possible mistakes?

Please help...

ghorrocks · December 19, 2012, 05:51

I assume you mean a time step size of 1e-6s. What makes you think this time step is adequate? Have you tried smaller? You will also probably need double precision.

Prateek garg · December 19, 2012, 06:08

I have modeled DDT earlier with fuel/air mixture already defined in the domain, at that time I took the same time step size. In this case I have also tried 1e-08 s but it didn't worked. So, I am afraid if there is mistake in physics setup.

December 19, 2012, 04:44	Igniting mixture	#1
Prateek garg Member Prateek Join Date: Mar 2012 Location: Bangalore Posts: 32 Rep Power: 14	Hi Friends, I am trying modelling DDT (deflagration to detonation transition). My first step was to create a uniform mixture of Jet A vapor and air which I have done successfully. During my second step I want to ignite this mixture to model DDT. While doing this I made a new case file. in this new file I changed the air and fuel inlets into wall, made a high temperature primitive region (to initiate ignition) and defining the reactions. While defining run I am using the result file of the previous simulation (mixture formation) trying to run it but it always end up with error. once it end up with Stack overflow then I reduced the time step. but it again stopped with error. For new simulation I am taking time step size as 10^6 sec and time duration of .001 sec. but still there is an error. Can someone tell me If this is the right way to go or what could be the possible mistakes? Please help...

December 19, 2012, 06:08	Ignition modeling	#3
Prateek garg Member Prateek Join Date: Mar 2012 Location: Bangalore Posts: 32 Rep Power: 14	I have modeled DDT earlier with fuel/air mixture already defined in the domain, at that time I took the same time step size. In this case I have also tried 1e-08 s but it didn't worked. So, I am afraid if there is mistake in physics setup.

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December 19, 2012, 05:51		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	I assume you mean a time step size of 1e-6s. What makes you think this time step is adequate? Have you tried smaller? You will also probably need double precision.