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Modelling Flettner rotors with Lifting Line Free Vortex theory
Hello,
For a project, I need to evaluate the aerodynamic interactions between a wind turbine (especially its wake), and a Flettner rotor positionned behind the turbine.
I consider QBlade and the LLFVW theory to model this phenomenon, considering the Flettner rotor as a lifting line with known lift and drag coefficients. Has anyone already done something similar ? If someone has an experience feedback or any consideration regarding this kind of modelling, it would be appreciated !
Best regards,
Lucas
Hi Lucas,
while I havent got experience modelling a Flettner rotor as a lifting line, the setup you propose should work in principle.
However, to set this up you would need the multi-turbine simulation capabilities of QBlade-EE (QBlade-CE is limited to single turbine simulation only).
Best regards,
David
Hi David,
Thanks for your fast answer. I’m gonna contact QBlade team to discuss the purchase conditions of QBlade-EE.
Regarding this Flettner modelling project, would you have any thoughts about how to adress that ? What would be your approach ?
Hi Lucas,
For a first engineering model, I would treat the Flettner rotor as a quasi-steady rotating-cylinder force element rather than as a conventional airfoil.
For a fixed RPM and an approximately fixed inflow velocity, one practical approximation would be to use calibrated constant CL and CD values from rotating-cylinder data at the corresponding spin ratio. This could be represented by an artificial polar with nearly constant CL and CD over the angle-of-attack range.
For a wider operating range, a single static polar would not be sufficient. In that case, CL and CD should depend at least on spin ratio and Reynolds number, and ideally also include finite-span and end-plate corrections.
Another option would be to apply the Flettner rotor loads as external forces through QBlade’s SIL interface.
This would allow a more granular modelling approach, for example by coding the Flettner force model in a Python script and applying the resulting loads directly to the structure.
I would therefore start with a simple calibrated constant-coefficient model for one operating point, validate the integrated forces, and then extend the model if the operating range becomes wider.
Best regards,
David
Thanks for your answer.
With QBlade EE, what kind of output could I have ? Does it compute the velocity field ? The pressure field ? Or only the loads ? It would be interesting to have velocity and pressure fields to make sure that the interactions between the wind turbine and the Flettner rotor are accounted for.
Best regards,
Lucas
Hi Lucas,
when using the LLFVW simulation in QBlade-EE you can obtain both the aerodynamic loads and the velocity field.
The velocity field can be evaluated for example through cut-planes, so you can inspect the wake and the induced velocities between the wind turbine and the Flettner rotor.
A pressure field is not computed, as the LLFVW method is not a CFD method and does not solve the full flow field around the bodies.
So for this type of model the interaction would be accounted for through the induced velocities and resulting loads, but not through a resolved pressure distribution.
Best regards,
David
