different solutions for the same problem!

Ema40 · February 14, 2016, 12:04

Hello,

I am simulating a very low speed turbine (transient simulation, VOF model). I run the simulation and monitor the torque at the shaft. Then, I have re-run again the same simulation, identycal, with the same conditions, discretization, ect. The results (the shaft torque) has changed of 20-25%...very strange..It does not happen always, only few times, but it is strange.

Do you know why? Caos?

Thank you

hwet · February 16, 2016, 04:45

Did you initialize again?
if not you will ofcourse get different results, it just means that your transient simulation has yet not reached steady state. continue the simulation till the result gets constant.

Ema40 · February 16, 2016, 05:33

Thank you. Yes, I did.
Consider that the transient time of my simulation has a physical meaning. My transient time is physical, not only a numerical transient time.

Yes, I initialized the solution, but in the same way of the other simulation, exactly the same.

Thank you

February 14, 2016, 12:04	different solutions for the same problem!	#1
Ema40 Senior Member Join Date: Oct 2014 Posts: 124 Rep Power: 12	Hello, I am simulating a very low speed turbine (transient simulation, VOF model). I run the simulation and monitor the torque at the shaft. Then, I have re-run again the same simulation, identycal, with the same conditions, discretization, ect. The results (the shaft torque) has changed of 20-25%...very strange..It does not happen always, only few times, but it is strange. Do you know why? Caos? Thank you

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February 16, 2016, 04:45		#2
hwet Senior Member Join Date: Mar 2014 Posts: 375 Rep Power: 13	Did you initialize again? if not you will ofcourse get different results, it just means that your transient simulation has yet not reached steady state. continue the simulation till the result gets constant.

February 16, 2016, 05:33		#3
Ema40 Senior Member Join Date: Oct 2014 Posts: 124 Rep Power: 12	Thank you. Yes, I did. Consider that the transient time of my simulation has a physical meaning. My transient time is physical, not only a numerical transient time. Yes, I initialized the solution, but in the same way of the other simulation, exactly the same. Thank you