Viscous interpolation with analysis-defined flap deflections

[mr0sg]

Hello everyone,

I am a new Flow5 user and have been following the¡ YouTube series by @techwinder. One point mentioned in Video 5 (Viscous Drag) caught my attention, and I would like to make sure I have understood it correctly.

As explained in the video, when trailing-edge flap deflections are defined in the Flaps tab of the analysis window (the new workflow introduced in Flow5), it is recommended to use XFoil on the fly for viscous calculations, since the Interpolated (XFLR5 method) would use 2D polars corresponding to the undeflected airfoil, leading to inaccurate viscous predictions.

My question is the following:

If I generate additional 2D polars for several flap deflections, can Flow5 make use of those polars during the interpolated viscous analysis, or are they ignored because the flap deflection is now introduced only at the 3D analysis stage?

In other words, is XFoil on the fly always the recommended (or required) approach whenever flap deflections are specified in the analysis, regardless of whether deflected-airfoil polars have already been generated?

Thank you very much, and apologies if this is a basic question. I am still making my way around the software.

Also wanted to thank the developers, I am trully learning a lot!

[techwinder]

The short answer is that flow5 cannot interpolate among several flap deflections. I considered it at one point but it made things overly complicated.
It uses the polar mesh of the airfoil with no flap deflection, if available.
Viscous estimations on the fly are required if the flaps are deflected.

André

[mr0sg]

Okey, I will take that into consideration. Thank you André for your prompt response.