Unsteady Aerodynamics Turning Off

Discuss the theory and modeling of rotor aerodynamics.

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Unsteady Aerodynamics Turning Off

Postby Sam.Ramsahoye » Thu May 21, 2020 7:06 am


I'm getting warning messages saying unsteady aerodynamics have been turned off. Does this new condition without unsteady aerodynamics persist for the entirety of the simulation?

Could this explain why my power, thrust curves appear to be insensitive to turbulence intensity?

Best wishes,

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Re: Unsteady Aerodynamics Turning Off

Postby Jason.Jonkman » Thu May 21, 2020 10:51 am

Dear Sam,

In AeroDyn v15, warnings regarding “turning off unsteady aerodynamics due to high angle-of-attack” are triggered if the local angle of attack at a given airfoil exceeds the value of input parameter UACutout, as specified in the airfoil data input file (if set to DEFAULT, UACutout = 45 degrees). You can eliminate this warning by setting UACutout higher or by ensuring the angles of attack don’t get so high (e.g. by setting proper initial conditions).

For each aerodynamic analysis node that triggers this warning, the UA model will be disabled for the entirety of the simulation.

I doubt that the disabling of UA is resulting in the insensitivity to turbulence intensity that you reported earlier.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901

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