  We describe a semi-structured method for the generation of high-order hybrid
meshes suited for the simulation of high Reynolds number flows. This is
achieved through the use of highly stretched elements in the viscous boundary
layers near the wall surfaces. CADfix is used to first repair any possible
defects in the CAD geometry and then generate a medial object based
decomposition of the domain that wraps the wall boundaries with partitions
suitable for the generation of either prismatic or hexahedral elements. The
latter is a novel distinctive feature of the method that permits to obtain
well-shaped hexahedral meshes at corners or junctions in the boundary layer.
The medial object approach allows greater control on the "thickness" of the
boundary-layer mesh than is generally achievable with advancing layer
techniques. CADfix subsequently generates a hybrid straight sided mesh of
prismatic and hexahedral elements in the near-field region modelling the
boundary layer, and tetrahedral elements in the far-field region covering the
rest of the domain. The mesh in the near-field region provides a framework that
facilitates the generation, via an isoparametric technique, of layers of highly
stretched elements with a distribution of points in the direction normal to the
wall tailored to efficiently and accurately capture the flow in the boundary
layer. The final step is the generation of a high-order mesh using NekMesh, a
high-order mesh generator within the Nektar++ framework. NekMesh uses the
CADfix API as a geometry engine that handles all the geometrical queries to the
CAD geometry required during the high-order mesh generation process. We will
describe in some detail the methodology using a simple geometry, a NACA wing
tip, for illustrative purposes. Finally, we will present two examples of
application to reasonably complex geometries proposed by NASA as CFD validation
cases.
