Characterization of Sharp-Edged Airfoils Using LES
Large-Eddy Simulations are performed to characterize the flow over a sharp-edged (retreating) NACA0015 wing section. The goals were to 1) demonstrate the need for three-dimensional simulations, as oppposed to less-expensive two-dimensional simulations; 2) assess the necessary spanwise width to capture the three-dimensional structures and compare to the necessary width for blunt (advancing) airfoils and 3) compare differing angles of attack for three-dimensional simulations to explore flow separation phenomena. Comparisons were made between the simulations as well as experimental results. Two-dimensional simulations are inaccurate because the absence of a third dimension does not allow for spanwise instabilities to develop as are necessary for true breakdown to turbulence. In addition, it was discovered that a spanwise width of 40% of the airfoil chord length is necessary to allow for proper development of spanwise structures, which is twice what is needed for an advancing airfoil. Finally, asymmetric vortex shedding at α=15° was observed and the details of this structure are investigated.
For a summary slideshow of this research, click here.
For a complete video gallery of this project, click here.