code_saturne User's Forum

Hello,

I have a question regarding the above mentionned item. while activating the thermal model in celsius, the xml file shows a reference temperature in the xml file of 1273,15 as you can see hereafter :
<reference_values>
<pressure>101325</pressure>
<velocity>1</velocity>
<temperature>1273.15</temperature>
</reference_values>

But I read in the documentation that this temperature should be 298.15 if the reference temperature displayed in the xml file is the trefth. I don not know if this is normal or not. Can someone tells me if I am correct suggesting that this temperature should be 298.15 instead of 1273.15, and what can be the impacts ?

Thanks.

Hello,

Yes, you are correct (and I had already mentioned this to colleagues some weeks ago), but there is usually no impact:

- "trefth" does not seem to be modified by the GUI. The value modified is "t0"

- This reference temperature (t0) is used automatically only for some specific physical models (meteo, and combustion), but in this case, you can set its value in the GUI, and the default is set to a correct value (293.15K)

- "t0" could be used in an MEI expression for physical properties, in which case you would need to have a correct value, but you could just as easily define another local variable for the reference temperature, so the issue is very minor (except for scaring users).

I am not sure we'll have time by release of 3.1 (early June), but by 3.2 (October), I hope that for better clarity, we can either define t0 only when using the associated models, or always allow the user to define it, even when not used, but not have some intermediate solution such as we have now).

Regards,

Yvan

OK, thank you Yvan.

Hello again Yvan,

I am using user physical properties. If I well understood this can be a problem. To overcome this, can I manually change this value in the xml file before lanching the calculation?

Thanks.