[ckm2]

Hello,

I am currently running a transient simulation.

Between the exit of the flow from domain 1 to domain 2 I used the profile transformation.

In the menu "solver control" I have set the convergence criterion of type RMS with 10^-4 and maximum 5 "Coeff. Loops" (see screenshot 1)

In the menu "Transient Blade Models" I have set 1200 "timesteps/period" and 2 "periods per run". (see screenshot 2)

My simulation keeps calculating even after timestep 2400. In another attempt, I ran the simulation to over 3000 timesteps. Am I misunderstanding something or should my simulation be done after 2400 time steps?

I am also confused by the plots in the Solver Manager. The plots shown in screenshot 3 are from the .res file after I stopped the simulation.
Does my simulation not reach convergence or how should I interpret these plots?

I don't know what to do and hope you can help me!

Thank you!

Greetings
Christian

[Opaque]

Would you mind posting the diagnostics at the beginning of any of your time steps? from the header TIME STEP ...

Never seen that.

May I ask why are you using 1200/period? is it not overkill? What kind of signal are you expecting? I cannot imagine you can capture the "steady-periodic" flow in two periods.

What kind of precalculations have you done to come up with such a timestep?

[ckm2]

Thanks for the answer!

Attached is a screenshot of the header of the first timestep.

Excuse me, but I am still quite new in this area.

What do the values in "timesteps/period" and "periods per run" mean exactly? Maybe I misunderstood something and caused the overkill.

My thought process behind the 1200/period was as follows.
So that stator and rotor are about the same size, in my case 12 rotor segments and 1 stator segment are necessary. (for profile transformation)
1200/12 is 100, so I can analyze the behavior of one rotor segment in 100 time steps.
The prevailing flow has some vortex structures and I thought this would be a suitable value.

[Opaque]

Originally Posted by ckm2

Thanks for the answer!

Attached is a screenshot of the header of the first timestep.

Excuse me, but I am still quite new in this area.

What do the values in "timesteps/period" and "periods per run" mean exactly? Maybe I misunderstood something and caused the overkill.

My thought process behind the 1200/period was as follows.
So that stator and rotor are about the same size, in my case 12 rotor segments and 1 stator segment are necessary. (for profile transformation)
1200/12 is 100, so I can analyze the behavior of one rotor segment in 100 time steps.
The prevailing flow has some vortex structures and I thought this would be a suitable value.

From the header, I can see you started the simulation from t = 0. Also, that one timestep is effectively 0.001 of the pitch which is extremely small. You said you want about 100 timesteps per pitch of the rotor; therefore, you must increase your timestep by at least 10 and the first time step will be then 0.01 of the pitch in your model (not possible to decipher how many passages you have in your model).

A factor of 10, means 120 timesteps/period. You also used an expression for the period; hence, not possible to know how you based your period calculation. I guess you mixed period of 1 revolution with the period of interest.

In general you want to timestep not to move more than the smaller pitch the smallest face in the domain interface will move. You can then reduce it from there.

[ckm2]

Originally Posted by Opaque

From the header, I can see you started the simulation from t = 0. Also, that one timestep is effectively 0.001 of the pitch which is extremely small. You said you want about 100 timesteps per pitch of the rotor; therefore, you must increase your timestep by at least 10 and the first time step will be then 0.01 of the pitch in your model (not possible to decipher how many passages you have in your model).

A factor of 10, means 120 timesteps/period. You also used an expression for the period; hence, not possible to know how you based your period calculation. I guess you mixed period of 1 revolution with the period of interest.

In general you want to timestep not to move more than the smaller pitch the smallest face in the domain interface will move. You can then reduce it from there.

Okay thanks already!

I will take a closer look again.

Assuming I use 120 timesteps per period, what effect does the value of "periods per run" have on the simulation?

For example I use 10 periods per run (reasonable value?), then my simulation should be finished after 1200 timesteps.

Thanks!