RMS Values in RANS

  • Last Post 21 November 2018
krany3 posted this 16 November 2018

I'm trying to check the rms vaules of the temperature in RANS. But, the rms temperature value is zero everywhere. Also, I don't see rms velocity in Fluent for RANS. How can see the rms velocity values? Why the rms temperature is zero ?

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kkanade posted this 19 November 2018

Can you please give more information.

What sampling interval you used? How did you plot rms values? Did you check global or auto range in contours?

How many time steps you ran? what are input conditions?

Please insert images also. 

krany3 posted this 19 November 2018

The case that I ran was a steady case. The rms temperature value is zero and I don't see an option in Fluent to check the rms velocity values. 

My inlet conditions are 300K temperature, modeled at atmospheric pressure and 2g/s mass flow rate.

rwoolhou posted this 19 November 2018

What other boundaries did you add to alter the temperature? In R19 the steady statistics will be in the "Steady Statistics" part of the Fluent Post Processing: velocity & pressure look to be included in the statistics by default. 

krany3 posted this 20 November 2018

I did not change any other variable. Since it's combustion, I provided the equivalence ratio of 0.67. I ran my simulations in R18.1. Will I be able to see the steady statistics if I open the case and data files in R19?

rwoolhou posted this 20 November 2018

Not unless they're also recorded in R18.x   this is why we always recommend using the latest build: why learn on the older versions? 

krany3 posted this 20 November 2018

I did not have the full academic version of R19. So, I had to use R18.1. 

I've one more question. Fluent is displaying same contours for RMS and RMSE. When I tried to plot the RMS values in post processing, it plotted the same values as RMSE. What is the reason for not displaying the RMS values?

rwoolhou posted this 21 November 2018

CFD Post doesn't always have all of the data available: Fluent only keeps some values in the .dat file, the rest are generated by the solver or not saved: otherwise the data files would be ridiculous sizes.  You can add data into the .dat file, and that's under File -> Data File Quantities from the top menu in Fluent. 

kkanade posted this 21 November 2018

Please check help manual. 

29.12.4. Data Sampling for Steady State Statistics