LW-P model

[Umair Ahmed]

Hi,
I am trying to run the LW-P combustion model with 4 peaks and adiabatic
conditions. The problem is that it is not showing any combustion. I am trying
to simulate a V flame anchored behind a cylinder. I have premixed methane air mixture
(with an equivalence ratio of 0.7) in the middle and air co-flow on the sides.
I have tried all a number of different values of ta, tstar ect. Does anyone
know what might be going wrong?
 
Thank you
Umair Ahmed

[Matthieu Guillaud]

ello,

it's difficult to answer your question without more informations.

Can you send your files?

Thanks.

Matthieu Guillau

[Umair Ahmed]

Hi,

I am using the 4 peak model. It seems to be working, but the
flame is not in the place where it should be. i.e. behind the cylinder. Instead
it stabilises at the edges of the burner exit. I am trying to model the
experiment done in this paper “Numerical simulation of a laboratory-scale turbulent
V-flame”. I think the problem might be due to converting it into 2D. I once did
get some reasonable results i.e. the flame stabalised behind the cylinder. But
this was done using the finer mesh than what I am using now, and K-Omega SST
with scalable wall-function (ideuch=2), so it was wrong.  I am attaching the files in zip format here.
The mesh is a bit over 10 mb in zip format, so it is divided in several parts.
If you could have a look at these files and let me know what I am doing wrong.
It might be the case that I have to model it in 3D. I also want to know about
the lwctss.f90 subroutine, it is mentioned there, that there is a constant Cf in
the dissipation term, which has not been included and is considered to be 1.  Could you please tell me about that constant? Thank
you for your help. Looking forward to hear from you.
 
Regards

Umair

[Umair Ahmed]

the mesh part 1

[Umair Ahmed]

mesh part 2

[Umair Ahmed]

mesh part 3

[Umair Ahmed]

Hi,
I have managed to get the LW-P model working for my test case. It works fine until I try and time average the results. All the values remain the same other than the temperature which increases by almost 5-6 orders of magnitude. I think there is a bug with memory allocation as the two listing files have temperature listed at different places. I was wondering if some one could look into this.
 
Regards
Umair

[Mickael Hassanaly]

Dear Umair,
Could you send me your latest routines? And your last results also.
Because it seems that your increase of temperature is about 2 degrees which appears to be very few.
 
Best regards
 
Mickaël Hassanaly

[Umair Ahmed]

Hi

I resolved the earlier problem by defining the length scale in usini1.f90. As it was set to almax(iphas) = -grand. I changed to the diameter of the cylinder in my case i.e.  almax(iphas) =0.002d0.

So now I get temperature rise up to 18632 degrees. Which is fine as I was expecting a value around this number. I have  uploaded the instantaneous results (from the tmp folder) on the url 
http://cfd.mace.manchester.ac.uk/twiki/ ... UmairAhmed.

Now I am having some trouble with time averaging the results from LW-P combustion model. I have uploaded the files on the url given above

 The files are under attachments tab at the bottom of the page.

The problem is that when I try and time average the results. All the values remain in a reasonable range  other than the temperature which increases by almost 5-6 orders of magnitude.  If you look in the tmp_Saturne folder for the two cases uploaded,  one with the averaging off (LW-P.) and the other with averaging on (LW-Pb). The temperatures in the listing files for the  LW-P are normal and temperatures for the LW-Pb are very high and non-physical. Also the temperature is listed in a different place in  LW-Pb listing file. Please have a look at these and let me know what is going wrong when the time averaging is switched on.  Looking forward to hear from you.

Regards

Umair Ahmed

[Mickael Hassanaly]

Dear Umair,

I send you a patch which will correct your problem.

Regards
 
Mickaël Hassanaly