Learning Forum

[TAnsys]

Hey!

I'm working on a project to simulate a physical 30m tube (0.5m dia) full of air, with the first 6m filled with premixed 9% Methane before being ignited by spark. This test is to better understand the behaviour of the flame front, pressures and temps over the 30m.

I'm struggling with 2 things.

1: In my physical test, the 6m section is separated by a ballon which is vaporised during the test. I want to fill my simulation in a similar way but whenever I create a split for the different sections it separates the simulation completely, I can't find a way to connect them but have different mixtures.

2: What setup should I use? Ive tried 2D and 3D premixed combustion (have been restricted to the 6m section) and species transport (with a velocity inlet of methane before spark ignition) with no good results.

I'm using fluid flow (fluent).

Any help or advice would be greatly appreciated, thankyou :)

[Rob]

1) Use Share Topology to connect the two volumes. Or multibody part (DesignModeler).
2) It's going to be very transient, what time step are you using? Why a velocity boundary, or is air & methane supplied after the initial premixed section is ignited?

[TAnsys]

Hi Rob, Thanks for your reply.
1) Thankyou this has worked for me connecting the two bodies.
2) Sorry, forget the velocity boundary I was just trying that when I couldn't connect the two mixtures.
I am currently using premixed combustion with spark ignition. The 30m simulation seems to be finished in 0.5 seconds or less, I am using a timestep of 0.001 seconds, for some reason when I reduce the timestep much more than that, the system does not combust, very frustrating haha.
Have you got any pointers for settings or anything else important I may have forgotten?
Thanks again

[Rob]

Run double precision.