Computational mesh

Two- and three-dimensional meshes have been generated for the clean airfoil and several Gurney-flap configurations. For the 2d case, the numerical C-grids contain $40,500$ cells in total ($453 \times 89$). The computational domain covers 7 chords upstream and 10 chords downstream of the configuration. The non-dimensional wall-distance of the first cell center remains below $y^{+}=1$ over the entire surface for an attached steady-flow case with the exception of the bluff trailing edge surface. Mesh dependency has been investigated by comparison to additional simulations using a $137,000$ cells mesh in the 2d case.

The Gurney-flap is represented by a single mesh line on both sides of which non-slip boundary conditions are applied (fig. ). Very fine mesh resolution is required in the boundary layers on the suction and the pressure side of the airfoil as well as in the shear layers behind the upper and the lower edges of the Gurney-flap.

Figure: Left: detail of the computational mesh around the HQ17 airfoil with Gurney-flap; right: mesh for a configuration with Gurney-flap and wake body.