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Section: New Results

Hybrid mesh adaptation for CFD simulations

Participants : Frédéric Alauzet [correspondant] , Lucille Tenkès, Julien Vanharen.

The aim of mesh adaptation is to generate the optimal mesh to perform a specific numerical simulation. It is nowadays a mature tool which is mathematically well-posed and fully automatic regarding tetrahedral meshes. Yet, there is still a strong demand for structured meshes, as many numerical schemes have proven to be more accurate on quadrilateral meshes than on triangular meshes, and as many favor structured elements in the boundary layer instead of tetrahedra to simulate viscous turbulent flows. Since no method can automatically provide pure hexahedral adapted meshes respecting alignment constraints, one solution is to use hybrid meshes, i.e. meshes containing both structured and unstructured elements. Accordingly, the following work focuses on hybrid metric-based mesh adaptation and CFD simulation on such meshes. Regarding hybrid mesh generation, the method relies on a preliminary mesh obtained through so-called metric-aligned and metric-orthogonal approaches. These approaches utilize the directional information held by a prescribed metric-field to generate right angled elements, that can be combined into structured elements to form a hybrid mesh. The result highly depends on the quality of the metric field. Thus, emphasis is put on the size gradation control performed beforehand. This process is re-designed to favor metric-orthogonal meshes. To validate the method, some CFD simulations are performed. The modifications brought to the existing Finite Volume solver to enable such computations has been developed.