We simulated compressible flow at Mach=0.5, Re=10,000 (based on total chord length) past a multi-body airfoil at zero angle of attack. The small scale features (i.e. nose and tails of each component) need to be resolved as well as the wake region and boundary layers. We used thin quadrilaterals on the components, and small elements at the noses and tails then blocked out using triangles in the far domain and a regular array of quadrilaterals in the wake.
1678 quadrilaterals and 3699 triangles were used in the mesh which was
created by Kirby [82] using SIMPLEX2D [83]
and his own advancing front/blocking routines. A summary of the
simulation parameters is given in table 7.5.
| Parameter | Value |
| Dimension | 2d |
| Re | approx. 10,000 based on total length |
| Mach | 0.5 |
 |
3e-5 |
| N-Range | 4 |
| KTri | 1678 |
| KQuad | 3699 |
| Method | Discontinuous Galerkin |
 |
 |
The final two-dimensional example is a simulation of flow past a multi-element airfoil shown in figure 7.9. The hybrid grid consists of 1638 quadrilaterals and 3739 triangles. The grid was constructed in three phases. Quadrilaterals were created using an advancing front method from each airfoil. A block of structured quadrilaterals was used to cover the wake region. The rest of the domain was covered with unstructured triangles using SIMPLEX2D. This is a Delauney-based grid generator with Steiner triangulation for guaranteed quality triangulation [4]. The Reynolds number is Re=10,000 based on the total length of the multi-element airfoil, and the freestream Mach number is M=0.5. A third-order expansion was used uniformly in each element everywhere in this problem. In figure 7.10 we plot instantaneous iso-Mach contours and streamlines around the airfoils. The flow is unsteady as it is evident from the vortex street present in the near-wake.