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Import of Polar does not show the operational points

Hello!

I have tried to import the polar coordinates of a sheet metal rotor geometry, i.e. a very flat curved foil. Since QBlade has no data for this type of foil, I tried to import my own polar coordinates. In the Airfoil Analysis module, only the first operating point is displayed after the analysis and I have no way to visualize the velocity distribution at different angles.

I imported the polars only in the order “AOA, cL, Cd” and no Cm. But shouldn’t the analysis module calculate the Cm? It doesn’t show that either. Maybe I need to change some settings or format to import the polars?

I would really appreciate some help.

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Hi Tibor,

in your project file you have created a polar that you simulated with XFoil that just converged for one or two operational points, this is the “pressure data” shown in the graphs.

For the polar that you imported such data is not available as you only imported Cl and Cd. The Moment coefficient also cannot be obtained from Cl and Cd alone but is an independent characteristic of the airfoil. If you import a polar without Cm the moment coefficient is set to zero.

BR,

David

Hi David,

thanks for the reply. I just created another airfoil section, which is slightly different to that one I just uploaded before. The polar data for this airfoil section is exactly the same; CL and CD over AoA.  But now an Moment coefficient can be shown.

The operational points are the Angle of Attack, right? So, if I understood your answer right, the operational points of the airfoil can only be shown if I import an polar data file with Lift, Drag, Moment and pressure data? Why can’t it be shown for the Lift and Drag only? Or are the operational points just for the pressure?

best regards

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Hi Tibor,

the operational point data for each AoA is only available if the polar was calculated in QBlade itself using the XFoil coupling.

If a polar is imported only the Cl, Cd and possibly Cm data is available.

BR,

David

 

A simulation of the Lillgrund windfram in QBlade, using the Dynamic Wake Meandering Model