SimScale CAE Forum

What does Reference Length Mean?

Hi, I try to analyze different kind of airfoils for formula students car. To get forces coefficients, Simscale want me to set a reference length for my object. I have read below link. I understood the reference area but I did’t get the reference length. Exactly which distance is that (point from where to where)?

I also curious about how it effect the result. In drag or lift coefficient formula, there is reference area. However the reference length is not included in formula. By saying formula I mean these formulas:

Lift Coefficient:
https://www.grc.nasa.gov/WWW/K-12/airplane/liftco.html#:~:text=The%20lift%20coefficient%20Cl%20is,times%20the%20wing%20area%20A.&text=The%20lift%20coefficient%20then%20expresses,dynamic%20pressure%20times%20the%20area.

Drag Coefficient:
https://www.grc.nasa.gov/WWW/K-12/airplane/dragco.html

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@core_support @cfd_squad - can you jump in here and help our user?

Best,

Jousef

Hey @okanarif

For the reference length it should be approximately the length of your geometry that is normal to the designated flow. For A wing profile a good estimate is the Chord length. If you have a multi-element wing then use the chord length of all elements. When you do your half/full car simulation, then switch to the length of the whole car.

I am not sure how this would effect results, but if your interested, then you could do a quick study and post the results. Im sure this would benefit other members

Dan

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Thank you so much.

You mean parallel to the flow? Chord of wing and length of car will be parallel to the flow.

Yes i meant parallel to the flow. Sorry if that was confusing

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Hi All,

As some additional information, the reference length does not take part in the calculation of drag and lift coefficients, so it would not affect their values.

You can find the equations that are used for drag and lift coefficients in SimScale in this article.

Cheers

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