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.