Questions regarding Equilibrium and Dynamic Inflow model

Wind & Water Rotor Aerodynamics
1

Hello,

I have some questions regarding some theoretical part of BEM and DynIn models.
I have note down the following limitations of BEM and DynIn models from user manual:
BEM:
BEM has problems at very high TSR where turbine is heavily loaded. The question is how high the TSR should be? Is there a particular value because I have a simulation where TSR reaches to 18 and the results are good.
DynIn:
DynIn has problem at low wind speeds and high TSR ------ the question is:Is there any particular ratio between these two values which states the limit beyond which DynIn is unstable?

   DynIn is unstable at high TSR where rotor acts like propellor  --- the question is how high this TSR should be? I have a simulation where DynIn becomes unstable at TSR ~ 7 - 8

Thanks
Chaitanya

2

Dear Chaitanya,

I’m not familiar with the limitation of BEM at high TSR. Are you referring to the comment regarding the Prandtl tip-loss model on the bottom of 5 of the old AeroDyn Theory Manual: nwtc.nrel.gov/system/files/AD_Theory.pdf? Regardless, we typically enable the Prandtl tip-loss model for all solutions with BEM.

I’m not sure I understand your question regarding DYNIN, but the instability of DYNIN at low wind speeds is discussed briefly in the following forum topic: Dynamic Inflow.

Best regards,

3

Hello Jason,

Thanks for the reply. My question regarding BEM actually refer to one the topic in forum:question concerning AeroDyn

Even my question regarding GDW (DynIn) is from the same topic.

Thanks
Chaitanya

4

Hi Chaitanya,

I’m not sure I can add anymore to what Rick said in that post. Perhaps Rick can comment further.

Best regards,