![]() ![]() Alternatively, it is also possible to employ a single-block mesh to fit the entire fluid domain. From the viewpoint of practicality and general application, the attractiveness of multi-block meshing is the ease of porting the mesh information into any commercial computer package. This approach offers immense flexibility in generating different grids in each block, particularly the increased mesh densities in blocks 2 and 5 capturing the developing boundary layer along the chord line between the leading and trailing edges and the expanding shock layers along the airfoil. The entire fluid region is subdivided into six contiguous blocks. One approach that can be suitably considered, especially for RANS simulations, is the block-structured or multi-block mesh (see Chapter 6) shown in Figure 7.54. Two different grid topologies that could be specifically used to solve the problem are illustrated in Figures 7.54 and 7.55. Here, the complete three-dimensional Navier–Stokes equations are solved to accommodate the spectrum of varying length scales that exists within the complicated fluid phenomena along the streamwise ( x), spanwise ( y), and vertical ( z) directions.ĬFD simulation: One challenging aspect of the CFD example of fluid flowing over an airfoil is the generation of appropriate meshes surrounding the geometry. ![]() At flows that are just below the speed of sound ( Ma = 0.2 is considered for the present problem), currently available computational hardware permits the use of DNS techniques to study the onset of flow instability and subsequent transition to turbulence subject to different inlet conditions. Numerical calculations are thus carried out in a two-dimensional fluid domain, and the calculations also include parametric investigations of the influence of different angles of attack on the expanding shock layers as the fluid travels past the airfoil. Because only time-averaged results are of primary interest, especially in RANS simulation, and since the length b is infinite, such conditions or assumptions mean that the flow is truly two-dimensional there is negligible spanwise variation of flow patterns and forces for a constant-chord airfoil. The Reynolds-averaged Navier–Stokes (RANS) equations are solved along with the shear stress transport (SST) turbulence model for supersonic flow ( Ma = 2.5) over the wing geometry. The CFD example in this section considers the subsonic and supersonic flows past an infinitely long airfoil.
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