BEDDOES dynamic Stall problem

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Arash.Mohammady
Posts: 4
Joined: Thu May 30, 2013 3:40 am
Organization: DTU
Location: Denmark

BEDDOES dynamic Stall problem

Postby Arash.Mohammady » Mon Jun 17, 2013 8:05 am

Hello,

I have some trouble or maybe it is better to called it I got some confusion about my result. I ran my simulations both with BEDDOES dynamic stall method and Steady dynamic stall. For each of them, I tried two methods to calculate my power.

In the first two simulations, I used RAMP wind speed:

!Time Wind Wind Vert. Horiz. Vert. LinV Gust
! Speed Dir Speed Shear Shear Shear Speed
0.0 4.0 0.0 0.0 0.0 0.0 0.0 0.0
5.0 4.0 0.0 0.0 0.0 0.0 0.0 0.0
990.0 30.0 0.0 0.0 0.0 0.0 0.0 0.0
9999.9 30.0 0.0 0.0 0.0 0.0 0.0 0.0


and in the next two simulations, I used different deterministic wind speeds (4 m/s up to 21 m/s)

Finally, when I compare the results, the simulations results of different deterministic wind speed with BEDDOES dynamic stall are different with the others. On the other hand, the rest of results are approximately equal to each other (i.e. deterministic wind speed with Steady Stall method is similar to RAMP wind speed Steady and BEDDOES stall method) :shock:

Now I got confused that which one of them could be correct. By the way I need to mention that I check the angle of attack along my blade and it has a good margin to the stall region, that is, the angle of attack along the blade vary at very low angles.
Could you please advise me about BEDDOES dynamic stall method in FAST? :?: :?: :?:

Thank you very much in advance for your help and your time.

Best Regards,
Arash

PS: I wanted to attach couple of my plots but it seems it is not possible.

Khanh.Nguyen
Posts: 8
Joined: Wed Mar 14, 2012 2:14 pm
Organization: NWTC
Location: Boulder, CO, USA

Re: BEDDOES dynamic Stall problem

Postby Khanh.Nguyen » Wed Jun 26, 2013 2:34 pm

Hi Aresh,

The “Beddoes dynamic stall” model in FAST/AeroDyn has three parts:
- Attached flow formulation includes (i) the shed wake effects due to circulation, similar to the Wagner, Kussner, and Theodorsen functions and (ii) the impulsive loadings due to the airfoil motion (of noncirculatory origin).
- Separate flow formulation models the dynamic effects of trailing-edge flow separation. Under static conditions, the results of this part should match the airfoil polar.
- Vortex lift formulation models the flow behavior of the leading edge vortices that create dynamic stall.

Thus, the proper name of this model should be “Beddoes-Leishman unsteady aerodynamic model” since dynamic stall is only a part of it.

The differences in your simulations are likely caused by the unsteady aero effects in the attached flow component of the model.

Cheers,

Khanh


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