[LemosLD]

Hi! Anyone know if fluent has a Macro for rms temperature? Modeling turbulent combustion the rms temperature is available as a result, but I want to use the information in one UDF. I did not find this on the manual.
Thank you!

[vinerm]

It depends on the combustion model. If you are using PDF, then you can try to use SV_T_RMS. It is defined, but whether available for UDFs or not, I am unsure.

[LemosLD]

Thank you for answer. I am using PDF model, but is a steady state simulation and I think that SV_T_RMS works in transient solutions. I tried to use but the result is a single value for all the domain. Not a field of rms temperature. The PDF model provide this field of rms temperature as a result, so I think it would be possible to use.

[vinerm]

Transient RMS are usually not saved in data file, but you are most likely right because its used in unsteady.h. As far as PDF based RMS is concerned, I don't see any such variable.

[vinerm]

There is a way to fetch any variable that is available in Contours, but I don't remember it right now. However, I am sure that it exists and you might find it either on this forum or online.

And there is a function called Calc_Pdf_RMS that requires three arguments. First and second are standard cell_t and Thread but third one is an integer. In my view, that might corresponds to the index of the RMS variables. So, if you want temperature, then you have to use the index as given in list when it displays in Contours. It returns a real value corresponding to that cell.

[LemosLD]

Thank you again, I tested Calc_Pdf_RMS(c,t,integer number) and the function return the rms value of mass fractions, according the index of species.
I think I am close to finding the rms temperature.

[Junjun Guo]

Hi Larissa,

Did you find the way to get the RMS temperature in UDFs? I face the same issue.

Thanks
Junjun

[LemosLD]

Hi! No, I still have not. I am using the PDF model for non-premixed combustion, so now I am trying integrating the temperature in PDF function. I am doing something that is ready, so it is the double of work, but I asked this question for many people and no one knows a macro for rms temperature. If I find I will write here, if you find could you do the same? Thanks!!

[Junjun Guo]

Originally Posted by LemosLD

Hi! No, I still have not. I am using the PDF model for non-premixed combustion, so now I am trying integrating the temperature in PDF function. I am doing something that is ready, so it is the double of work, but I asked this question for many people and no one knows a macro for rms temperature. If I find I will write here, if you find could you do the same? Thanks!!

I try to use Calc_Pdf_RMS(c,t,integer number), the integer number is one more than the number of species, if the mechanism you used has 47 species, then the integer number is 47, since the index of species starts from 0. In my case, it gives me the rms temperature which is the same with that in contour, but I don't know why should be this number.

[LemosLD]

Yes, it really works!!! When I tested I think it was only for species, but the last one is rms temperature! Thank you so much!
What do you mean, do you want to know how is calculate the rms temperature? Thank you!!

[Junjun Guo]

Originally Posted by LemosLD

Yes, it really works!!! When I tested I think it was only for species, but the last one is rms temperature! Thank you so much!
What do you mean, do you want to know how is calculate the rms temperature? Thank you!!

Root mean square in Fluent, it is probably not genuine!
In this post, they guess the rms in Fluent is not the genuine RMS as we normally learned. Do you know the equation used to calculate the rms in Fluent?

[LemosLD]

Actually I am testing this, I think the result of rms temperature is only about the fluctuating part, as commented in the post for velocity. However, I don't found this explication on the manual.

[Krutika Appaswamy]

Hi,

I have been trying to obtain the RMS of temperature (PDF method for combustion calculations) but the RMS temperature's XY plot is much lesser than expected. I read a couple of posts explaining the reason being it is the RMS of the fluctuations. I was wondering if there is any way to obtain the actual RMS values.
Thanks!