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-   -   Ansys CFX Vs. NACA Summary Report. Mismatch Result (http://www.cfd-online.com/Forums/cfx/23522-ansys-cfx-vs-naca-summary-report-mismatch-result.html)

Santiago Orrego. January 12, 2007 11:38

Ansys CFX Vs. NACA Summary Report. Mismatch Result
 
Hello. We are working on a NACA 4415 airfoil. We are trying to validate the model, making a comparation between the results from Ansys CFX and the summary report 824 from NACA, page 143.

The conditions of the NACA experimental Test are (if Im wrong please let me know): Re: 3e6 Density: 1.225 ???? kg/m3 Viscosity: 1.7986 ??? kg/m*s Chord= 2ft (0.6096m) Ref pressure= 1 atm ????

We assumed ISA conditions @ sea level. (if somebody know the conditions, please confirm us)

In CFX the conditions are: Re:3e6 Density: 1.225 kg/m3 Viscosity: 1.7986 kg/m*s Chord of the airfoil= 2ft (0.6096m) Ref pressure= 1 atm alfa= 4 turbulence model= SST turbulence intensity= 5% turbulence wall function=automatic Gas ideal @ 15C

for the iteration convergence: High resolution conservative max= 1e-4 autotimescale

meshed in ICEM. C grid hex elements, we used edge spacing, leaving the same spacing and changing number of nodes in the three meshes.

Hence: the results in CFX are: 1.Mesh: Elements 35466 - Y+:2.448 - Cd: 0.0301079 - Cl: 0.6131 2.Mesh: Elements 47886 - Y+:0.7881 - Cd: 0.029875 - Cl: 0.601245 3.Mesh: Elements 78606 - Y+:0.5475 - Cd: 0.0288936 - Cl: 0.589375

The results form NACA report are: Cl:0.81 Cd:0.0075

Can anybody can help us out? thanks for reading and contribuying.

Santiago - Andres - Colombia.

Santiago Orrego. January 13, 2007 12:00

Re: Ansys CFX Vs. NACA Summary Report. Mismatch Re
 
Hello Again. We modified some boundary conditions and we got more closer.

Cl= 0.78 Cd=0.013

The error in Cl is about 7%, but the error in the Cd is about 60%.

Is this correct? its possible to get an error <10% in the Cd ?

Thanks Santiago Andres

bill February 5, 2007 09:31

Re: Ansys CFX Vs. NACA Summary Report. Mismatch Re
 
use transition model

Santiago Orrego. February 5, 2007 12:05

Re: Ansys CFX Vs. NACA Summary Report. Mismatch Re
 
Thanks Mr Bill. Ww used Langtry Menter and it worked ok. We had problems with the convergence, but the results where ok. Thanks santiago


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