[anilkadam]

Hi friends, am working on flame jet impingement on flat plate. I want to know transient temperature change in flat plate after flame jet impingement.

Just to give a try, i run the fluent (steady) till the flame get stabilized n then i started "transient" with lower time steps and flame just extinguished after few time steps .

I would like to ask whether this problem can be solved with system coupling (Steady fluent simulation + transient thermal)??

Expecting experts opinions!!!

[LuckyTran]

I would double check your boundary conditions, etc. An unsteady simulation should not suddenly become extinguished. Anyway...

A simple calculation should reveal whether the heat conducted into the plate has any significant cooling effect on the flame temperature, it probably doesn't. If so, then yes. I would run a steady simulation to get the adiabatic wall temperature and heat transfer coefficient and then impose these onto a pure heat conduction problem. I don't think this requires system coupling (too fancy for me) but if you think you know how to do it then go ahead.

Alternatively, you only need to show that the cooling effect does not alter the flow. Then you can just freeze the flow solver and solve only the energy equation. This gives you the cooling effect on the flame and still lets you solve for the heat conduction into the plate. Hopefully this time the flame is not extinguished.

[anilkadam]

Thank U LuckyTran!!!!

yes its true, no effect of cooling on the flame temperature. Both suggestion looks great at the moment..first one i had thought of but second suggestion is just amazing..excited to see the result..once finished i will come back to u..

[anilkadam]

Hello LuckyTran ,
I am bit confused now!!!
"freeze the flow solver" mean to unable the flow equation from the solution control??
If yes then unfortunately i have to say that flame (flame using GRi mech 30 species for methane-air) is disappeared slowly with the time.

and

How to get adiabatic wall temperature as u have mentioned in first suggestion?? is it a wall temperature in adiabatic condition in steady solution!!!

[anilkadam]

Originally Posted by anilkadam

Hello LuckyTran ,
I am bit confused now!!!
"freeze the flow solver" mean to unable the flow equation from the solution control??
If yes then unfortunately i have to say that flame (flame using GRi mech 30 species for methane-air) is disappeared slowly with the time.

and

How to get adiabatic wall temperature as u have mentioned in first suggestion?? is it a wall temperature in adiabatic condition in steady solution!!!

As i mentioned earlier, initially am running steady simulation till the flame get stabilized without heating the plate (assigning constant plate temp BC) then while going to unsteady simulation, plate BC is updated to coupled BC.
Am i making mistake in procedure?? please suggest.

[LuckyTran]

Originally Posted by anilkadam

As i mentioned earlier, initially am running steady simulation till the flame get stabilized without heating the plate (assigning constant plate temp BC) then while going to unsteady simulation, plate BC is updated to coupled BC.
Am i making mistake in procedure?? please suggest.

I would do it the same way. Disable the flow equation from the solution control. If the flame still gets distinguished, that is interesting?

Yes, apply a steady state wall temperature and then change the boundary condition to coupled or something equivalent like setting the backside temperature of the plate to a set value. However, it seems like this approach inevitably results in the flame becoming extinguished. So what is happening?

Since this is not working, you can still do the original approach. Just map the appropriate boundary conditions and do transient heat conduction in a flat plate. There are many ways to do this. You can simply map the heat transfer coefficients over (note that this only works if the reference temperature is the same for both).

It is not a problem per se, but remember that the heat transfer coefficient is defined based on a specified reference temperature. Physically, the driving temperature is the adiabatic wall temperature but you don't need to worry about this. Just map the heat transfer coefficients over since your geometry is identical and you are not scaling anything.