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Implementing the eN method into OpenFOAM

Paper presented at the 6th Symposium on OpenFOAM in Wind Energy, June 13th-14th, 2018, Visby, Sweden
: Bouville, Olivier; Daniele, Elia; Stoevesandt, Bernhard; Plaut, Emmanuel

Fulltext urn:nbn:de:0011-n-5067702 (811 KByte PDF)
MD5 Fingerprint: 9d33fdbf44c62d620d7c002b9477637c
Created on: 24.8.2018

2018, 7 pp.
Symposium on OpenFOAM in Wind Energy (SOWE) <6, 2018, Visby>
Conference Paper, Electronic Publication
Fraunhofer IWES ()

This work deals with programming the transition to turbulence detection method denominated eN for the airflow around an airfoil. The OpenFOAM software contains several transition prediction methods but not the so called eN, based on linear stability analysis and solving the Orr-Sommerfeld equation with the computation of the amplification ratio N. This implementation uses the output of a C++ program computing the main boundary layer properties as a post-processing of a numerical simulation. The accuracy of the results obtained have been compared with those provided by XFOIL application, a FORTRAN tool developed by Drela that uses the eN method. The OpenFOAM simpleFoam solver and the k - ω - SST turbulence model have been adapted to run multi region simulations, where a laminar and a turbulent zone coexist. Moreover, the code computing the boundary layer properties performs run time checks to detect the transition to turbulence, i.e the boundaries of the two regions can be updated during the numerical simulations. For the sake of completeness the eN method has been implemented via two alternatives: a straightforward programming reproducing Drela’s method, and a coupling between a FORTRAN code from Cebeci and the transition prediction code. Simulations show that the present implementation outperforms the g γ - Req transition model when compared to the XFOIL results for the airfoil NACA 63-425.