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consistently underestimating lift on a naca 0024 profile.

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Old   May 2, 2014, 17:20
Default consistently underestimating lift on a naca 0024 profile.
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Jochem Grietens
Join Date: Nov 2013
Location: Belgium
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Dear colleagues,

I have been trying to make do a static analysis of a NACA 0024 airfoil in fluent at 5 degrees AoA. But i have consitently been underestimating the Cl. I need to validate the model in this static configuration to move on to a dynamic flapping motion model.

I created the airfoil in solidworks and exported it as a parasolid file. I used ICEM to create a structured grid arround the airfoil and a unstructured grid outside the structured one.

i am working at Re=200.000 with water rho=999.7kg/m³ U=0.866666667m/s and viscosity=0.00129961kg/m-s and chord 0.3m turbulent intensity = 2% turbulent viscosity ratio=10

I am using second order space discretisation with the SIMPLE scheme. As a turbulence model, i use k-omega SST after hybrid initialization (low reynolds number correction not applied).

After modelling i get convergence but i consistantly get an underestimation of the Cl. i get Cl = 0.34208 and Cd = 0.02255 while Airfoiltools tells me that it should be Cl=0.4949 and Cd=0.01732

I have attached the y+ curve along the airfoil edge , it is not around one but i already have a cell heigth of 0.0001m at the airfoil boundary so i don't know if this is where the error get's created.

I have a picture of the mesh in the attachement and the Cl monitor as well as the unscaled residuals.

Does anyone have an idea of what might be going wrong? or something i might try to fix this ?
Attached Images
File Type: jpg yplus.jpg (18.6 KB, 7 views)
File Type: jpg farmesh.jpg (97.4 KB, 6 views)
File Type: jpg meshclose.jpg (44.6 KB, 8 views)
File Type: jpg Cl.jpg (14.1 KB, 5 views)
File Type: jpg unscaled residuals.jpg (18.2 KB, 6 views)
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