Learning Forum

[AlexT]

Hi everyone, any help and opinion is appreciated. I am simulating airfoil profils (2D) in fluent 2020 R2 academic. In every simulation results are unrealistic. I have tried unsuccessfully several times to understand what is going wrong. I am a beginner with fluent, so I am definitely doing something wrong and I think you can help me. I emphasize that the mistake is always the same. 

Just an example, trying to have some results for the Eppler 420 airfoil.

Airfoil Eppler 420

Chord 140mm

AOA 15 deg

Importing .IGS file from Solidworks

K-ω SST (but I have also tested several models)

Inlet Velocity 20 m/s

here follows the whole process I performed:

[peteroznewman]

I recommend deleting the All Triangles Method mesh control you are using.nA major defect in the model is the mesh has no inflation layer. Below is an example of a mesh with an inflation layer on the airfoil boundary edge.nUse an Inflation mesh control. This example shows a 1 mm First Layer Height. Don't use 1 mm. nRead this discussion to determine the correct First Layer Height for your model.n/forum/discussion/1522/near-wall-treatmentn

[AlexT]

Arraythank you for your prompt reply! nI changed the triangle method I used and added an inflation layer on the airfoil boundary edge. I had better results but still unrealistic - really big coefficients. I guess I have to try hard to find the ideal mesh and setup. nΤhe strange thing is that in some tutorials users relatively easy and quick approach a logical if not ideal solution. n

[peteroznewman]

I assume you used Inlet Velocity components and did not leave it as the default of Normal to Surface. You didn't show that input so is it possible you forgot to change the default?n

[AlexT]

Yes right. I did not make any change to this field. So it is the default.nI only set the inlet velocity as 20 m/s. n

[AlexT]

nShould I change the default ?n(I hope I understood correctly about the input you mentioned):nn

[peteroznewman]

nYes, this is one reason why your lift and drag coefficients are way off.nThe Velocity Specification Method is not correct. The air is coming in normal to the semi-circle, that is directed toward the center of the circle where it collides with the wing.nYou want Components. You want the air coming in parallel to the X axis in a nice smooth air stream.nPut 20 m/s in the X component and 0 m/s in the Y component.n