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An octree-based algorithm for the generation of hexahedral element meshes is presented. The algorithm works in three steps: (i) The geometry to be meshed is approximated by an octree structure. (ii) An unstructured hexahedral element mesh is derived from the octree. (iii) The mesh is adapted to the boundary of the geometry. We focus on step (ii) and describe an algorithm that constructs a hex mesh for a given octree structure.

The present paper describes an unstructured hexahedral mesh generator for viscous flow simulations around complex 3D configurations. The first step of this method is the geometric adaptation of an initial non-body-fitted mesh by grid embedding. The resulting octree mesh is then fitted to the actual boundaries of the domain and its main features, such as sharp edges and corners, are captured. Degenerated cells resulting from body-fitting are removed using a splitting strategy and by insertion of buffer layers. Finally, in vicinity of solid walls, layers of highly stretched cells are marched directly from the quadrilateral surface mesh that is a by-product of the body-fitting process. Interfacing between the layer and octree meshes only requires the deformation of the octree to insert the layers. The resulting method is highly automated and significantly reduces turnaround times. To illustrate its capabilities, both internal and external applications are presented.