2D Large Eddy Simulation of Turbulent Boundary Flow around a Controlled-Diffusion Wing Section Using a Locally Refined Unstructured Grid
In this study, a 2D large eddy simulation of the flow around a thin, cambered, controlled-diffusion airfoil was carried out. An embedded local mesh refinement technique was used to achieve very fine near-wall resolution while maintaining a coarse mesh away from the airfoil. The flow was simulated at a geometric angle of attack of g• and a Reynolds number of 1.2x10s. Experimental observations show that at this angle of attack, the flow exhibits laminar leading edge separation, transition to turbulence after reattachment and vortex shedding at the trailing edge [1-3]. The embedded local mesh refinement technique was found to be very effective for selective grid refinement. A near wall resolution of y• :s:l and x+ ~ 20 was achieved. However, the solution developed numerical oscillations with a central-difference spatial discretisation. Discontinuities existed in the velocity field at the refinement interfaces which pointed to a possible error in interpolation of velocity gradients. A stable solution was achieved with a second-order monotone scheme (MARS) available in Star-CD software. The solution reproduced all qualitative features of the flow and was found to be in good agreement with the experimental results. However, the use of the monotone scheme suppressed the small-scale turbulent structures near the trailing edge.