RADIATION and time scaling

Altair Forum User

Hello,

i have a little question about the possibility of time scaling and the use of the radiation load collector.

I used the factor 10 (1sec in simulation=10sec in real time) to speed up my thermal analysis with radioss.

It works fine wenn i scale thermal conductivity and the heat transfer coefficent (for example convection) by the factor i used for speed up (10).

Is this although possible for the radiation? Because i don't see any way to scale this value in correct way...

 

With best regards

Kintsch

Altair Forum User

Hi Kintsch,

This /RADIATION is an imposed load condition. in this load card we have a time function identifier ( fct_IDT ) for the temperature of heat source. Here you can create a required time vs temperature function

Altair Forum User

I don't think this will work, a little example:

 

Convection:

 

Q=h_conv*(T_1-T_2)

with time scaling by 10 i just go to the h_conv value and scal it with the same value

h_conv=yy*10

 

Radiation:

Q=e*Boltzman_const*(T_1^4-T_2^4)

e = has to be a value between 0 and 1 .. so i don't have the possibility to scale this value over the emissionfactor

 

With the Time vs Temperature i only can scale an constant value, because T_1 is my sourounding Temperature and it is const. 303,15K.

 

With best regards

Kintsch

 

Altair Forum User

okay the Solution of the Problem is realy easy.

 

the emission hast to be a value between 0 and 1, but you can define values greater than 1.

So for example if you want to speed up your thermal calculation by a factor of 10 you just need to scale your emission factor.

e (with out scaling) = 0.6

e (with sclaing by 10) =6.0

 

works absolut fine.

If you want to solve radiation problems use the newest Radioss version (2017.2), with older version i had extrem deviations to the real temperature values!

 

 

With best regards

Kintsch